Postannealing effect on physical and electrical characteristics of BTS thin films. Leakage densities are given for an applied voltage of 10V
\r\n\tCongenital hearing loss means hearing loss that is present at birth. I have managed children with hearing loss for many years, and the most touching thing is the light that blooms on the face while the hearing-impaired child heard his mother's voice at first time. The scene of "happy tears" impressed me so much. To hear the voice that has not been heard is so pleasant, as if this ordinary listening experience is a supreme listening enjoyment.
\r\n\r\n\tAge-related hearing loss means a progressive loss of ability to hear high frequencies with aging, also known as presbycusis. Among them are the influence of internal and external factors such as genes, drugs and noise exposure. The studies pointed out that the brain stimulation of the hearing-impaired person is greatly reduced compared with subjects with normal hearing. The connection of auditory cortex and other brain areas has declined a lot, which is probably one of the important causes of dementia or even depression in the elderly.
\r\n\r\n\tNoise-induced hearing loss is hearing impairment resulting from exposure to loud sound. There is actually continuous and endless noise in many workplaces, which may cause chronic and cumulative damage. Some young people often work hard but easily neglect to protect themselves. In addition, in recent years, entertainment noise (such as nightclubs, concerts, and personal listening devices) has caused hearing impairment in young people. These should be avoidable and preventable.
\r\n\r\n\tHearing Science is the study of impaired auditory perception, the technologies and other rehabilitation strategies for persons with hearing loss. Public health has been defined as "the science and art of preventing disease", improving quality of life through organized efforts. To avoid the “epidemic” of hearing loss, it is necessary to promote early screening, use hearing protection, and change public attitudes toward noise.
\r\n\r\n\tBased on these concepts, the book incorporates updated developments as well as future perspectives in the ever-expanding field of hearing loss. Besides, it is also a great reference for audiologists, otolaryngologists, neurologists, specialists in public health, basic and clinical researchers.
",isbn:"978-1-83968-678-8",printIsbn:"978-1-83968-677-1",pdfIsbn:"978-1-83968-679-5",doi:null,price:0,priceEur:0,priceUsd:0,slug:null,numberOfPages:0,isOpenForSubmission:!1,hash:"a4b7dbb02ba00e7412422cd5dbffa029",bookSignature:"Dr. Tang-Chuan Wang",publishedDate:null,coverURL:"https://cdn.intechopen.com/books/images_new/10529.jpg",keywords:"Hidden Hearing Loss, Plasticity, Electrophysiology, Otoacoustic Emission, Newborn Hearing Screening, Genetics, Aging, Hearing Aids, Noise Exposure, Occupational Hearing Loss, Epidemiology, Prevention",numberOfDownloads:null,numberOfWosCitations:0,numberOfCrossrefCitations:null,numberOfDimensionsCitations:null,numberOfTotalCitations:null,isAvailableForWebshopOrdering:!0,dateEndFirstStepPublish:"September 3rd 2020",dateEndSecondStepPublish:"October 1st 2020",dateEndThirdStepPublish:"November 30th 2020",dateEndFourthStepPublish:"February 18th 2021",dateEndFifthStepPublish:"April 19th 2021",remainingDaysToSecondStep:"3 months",secondStepPassed:!0,currentStepOfPublishingProcess:4,editedByType:null,kuFlag:!1,biosketch:"Dr. Tang-Chuan Wang is an excellent otolaryngologist-head and neck surgeon in Taiwan; a research scholar of Harvard Medical School and University of Iowa Hospitals. He worked in the Hospital of the University of Pennsylvania, Boston Children's Hospital, and Massachusetts Eye and Ear. Due to his contribution to biomedical engineering, he was invited into the executive committee of HIWIN-CMU Joint R & D Center in Taiwan.",coeditorOneBiosketch:null,coeditorTwoBiosketch:null,coeditorThreeBiosketch:null,coeditorFourBiosketch:null,coeditorFiveBiosketch:null,editors:[{id:"201262",title:"Dr.",name:"Tang-Chuan",middleName:null,surname:"Wang",slug:"tang-chuan-wang",fullName:"Tang-Chuan Wang",profilePictureURL:"https://mts.intechopen.com/storage/users/201262/images/system/201262.gif",biography:'Dr. Tang-Chuan Wang is an excellent otolaryngologist – head and neck surgeon in Taiwan. He is also a research scholar of Harvard Medical School and University of Iowa Hospitals. During his substantial experience, he worked in Hospital of the University of Pennsylvania, Boston Children\'s Hospital and Massachusetts Eye and Ear. Besides, he is not only working hard on clinical & basic medicine but also launching out into public health in Taiwan. In recent years, he devotes himself to innovation. He always says that "in theoretical or practical aspects, no innovation is a step backward". Due to his contribution to biomedical engineering, he was invited into executive committee of HIWIN-CMU Joint R & D Center in Taiwan.',institutionString:"China Medical University Hospital",position:null,outsideEditionCount:0,totalCites:0,totalAuthoredChapters:"2",totalChapterViews:"0",totalEditedBooks:"2",institution:{name:"China Medical University Hospital",institutionURL:null,country:{name:"Taiwan"}}}],coeditorOne:null,coeditorTwo:null,coeditorThree:null,coeditorFour:null,coeditorFive:null,topics:[{id:"16",title:"Medicine",slug:"medicine"}],chapters:null,productType:{id:"1",title:"Edited Volume",chapterContentType:"chapter",authoredCaption:"Edited by"},personalPublishingAssistant:{id:"252211",firstName:"Sara",lastName:"Debeuc",middleName:null,title:"Ms.",imageUrl:"https://mts.intechopen.com/storage/users/252211/images/7239_n.png",email:"sara.d@intechopen.com",biography:"As an Author Service Manager my responsibilities include monitoring and facilitating all publishing activities for authors and editors. From chapter submission and review, to approval and revision, copyediting and design, until final publication, I work closely with authors and editors to ensure a simple and easy publishing process. I maintain constant and effective communication with authors, editors and reviewers, which allows for a level of personal support that enables contributors to fully commit and concentrate on the chapters they are writing, editing, or reviewing. I assist authors in the preparation of their full chapter submissions and track important deadlines and ensure they are met. I help to coordinate internal processes such as linguistic review, and monitor the technical aspects of the process. As an ASM I am also involved in the acquisition of editors. 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Venkateswarlu",coverURL:"https://cdn.intechopen.com/books/images_new/371.jpg",editedByType:"Edited by",editors:[{id:"58592",title:"Dr.",name:"Arun",surname:"Shanker",slug:"arun-shanker",fullName:"Arun Shanker"}],productType:{id:"1",chapterContentType:"chapter",authoredCaption:"Edited by"}}]},chapter:{item:{type:"chapter",id:"18049",title:"Barium Titanate-Based Materials – a Window of Application Opportunities",doi:"10.5772/18196",slug:"barium-titanate-based-materials-a-window-of-application-opportunities",body:'Since it was discovered in 1945, barium titanate (BT) attracted much attention to researchers, becoming one of the most investigated ferroelectric materials due to good electrical properties at room temperature, mechanical and chemical stability and the easiness in its preparation. It is known that above the Curie temperature, the crystalline barium titanate has a cubic, perovskite-like structure as shown in figure 1.
Crystalline structure of BT material above Curie temperature
Below the Curie temperature, the crystalline cell is suffering a series of changes: to tetragonal (at 120ºC), from tetragonal to orthorhombic (at 0ºC) and from orthorhombic to rhombohedral (at –90ºC) in which the material has ferroelectric properties.
Theories concerning the ferroelectric behavior of crystalline materials that have a perovskite structure pinpoint the important role played by the spatial oxygen arrangement having an ion in its center, to the ferroelectrical properties. Taking this into consideration it is easy to predict that a change in spatial alignment of the oxygen octahedra or a substitution of the central ion (B-site substitution) can modify the ferroelectric behavior of the material. Change in spatial alignment of the oxygen octahedra can be also made by (so called) A-site substitution, when an A-site ion is substituted with another ion. In the case of barium titanate, it has been found that substitutions can make the temperature of paraelectric to ferroelectric transition to shift towards lower or higher values and, in some conditions, the temperature of dielectric constant maxima will be affected by the frequency of the applied field (relaxor behavior). An A-site substitution, for example substituting Ba2+ with Sr2+ or Pb2+, is responsible for shifting the temperature region in which the ferroelectric properties are present while the values of permittivity remain relatively large. This is good from the applications viewpoint because the possibility of shifting Curie temperature and the selection of the sector for the temperature dependence for dielectric constant and dielectric loss broadens the application area of these BT-based materials. The representative material in this class is (Ba1-x,Srx)TiO3 (BST), one of the most studied solid solution due to its stability and the wide range of possible applications that can use its electrical properties.
A B-site substitution is also responsible of changing the degree of ordering in the solid solution resulting in a shift of Curie temperature and the appearance of the relaxor behavior when the local ordering of B-sites will make it favorable. In this category there is no widely studied BT-based material because their properties were comparable to other ferroelectric materials such as lead zirconate titanate (PZT), pure barium titanate, lead titanate or even barium strontium titanate. However, it has been found that small amounts of BaZrO3 or BaHfO3 included in BT can make it a candidate material for pyroelectric sensor, having electrical characteristics superior of those of lead lanthanum zirconate titanate (PLZT) or BST, materials that were commonly used for such applications.
As mentioned earlier, (Ba,Sr)TiO3 (BST) solid solutions are one of the most investigated ceramic materials because the shift of ferroelectric phase transition towards lower temperatures can easily be controlled by adjusting the Ba/Sr ratio while maintaining acceptable high dielectric constants coupled with good thermal stability. Ba (Ti,Sn)O3 (BTS) solid solutions are another subclass of materials that can be used for specific application. For a given application, to achieve the desired properties in the BST or BTS system, compositional control should be considered along with the preparation method and/or deposition method in the final device structure.
From many applications that can incorporate BT-based materials, here only optimization for two applications will be discussed in detail: dielectric bolometer mode of infrared sensor and embedded multilayered capacitor structures. Since the requirements for ferroelectric materials suitable for dielectric bolometer mode of infrared sensor and embedded multilayered capacitor structures are different, a good selection of ferroelectric material and fabrication method is necessary to ensure high quality ceramic layers for these applications. As a result, BTS thin films have been fabricated using metal-organic decomposition method as a suitable process to ensure good quality films for dielectric bolometer mode of infrared sensing applications. In the case of films for embedded multilayered capacitor applications, since the target require a low temperature fabrication technique, BST thick films have been fabricated using a relatively new deposition technique called aerosol deposition method, developed at National Institute of Advanced Industrial Science and Technology by Dr. Akedo, one of the coauthors of this paper, a fabrication method that allows fabrication of thick and dense ceramic layers at room temperature.
One important characteristic for a material to be suitable for dielectric bolometer (DB) mode of infrared sensor applications is to have a large Temperature Coefficient of Dielectric constant (TCD).
From 1990, Ba(Ti1-x,Snx)O3 solid solution captured the attention of the researchers because of his stable ferroelectric properties in the vicinity of the Curie point that makes it a good candidate for specific applications. Because it belongs to a class of ferroelectric materials that show a diffuse phase transition (DPT) who have promising properties behavior that can be used for various applications such as sensors, actuators or high permittivity dielectric devices, this solid solution captured the attention of many research groups as a suitable active material. Investigation made with bulk Ba(Ti1-x,Snx)O3 samples revealed that, if BaSnO3 content is 30% or more, the solid solutions of Ba(Ti1-x,Snx)O3 have relaxor behavior (Mueller et al., 2004; Lu et al., 2004; Yasuda et al., 1996; Xiaoyong et al., 2003). Moreover, Yasuda and al. observed a deviation of the dielectric constant from the Curie-Weiss law (that is specific for relaxor ferroelectrics) even when BaSnO3 content is between 10 and 20%, but only in a narrow temperature region above Curie point, and a relaxor behavior for samples in witch the BaSnO3 content is above 20%.
More recently, some authors see in Ba(Ti1-x,Snx)O3 a candidate to replace (Ba,Sr)TiO3 in microwave applications (Lu et al., 2004; Jiwei et al., 2004). Jiwei et al. showed that, in some conditions, tunability of a metal-ferroelectric-metal (MFM) structure could be as high as 54% at an applied field of 200 kV/cm and a frequency of 1 MHz.
A more important indirect result has shown by Tsukada et al. where, from the dielectric constant versus temperature for a Ba(Ti1-x,Snx)O3 (BaSnO3 content of 15%) thin film with a thickness of 400 nm deposited by PLD on Pt/Ti/SiO2/Si, a value close to 11% at 250C can be calculated.
In the processing of the thin films, the goal is not only to reduce the cost and time in fabrication process but, more important, is to optimize the film properties for specific applications. Metal-organic decomposition process (MOD) has some advantages in comparison with other widely used deposition techniques: precise control of stoichiometry, high homogeneity, large area of deposition and simple equipment and process flow. However, one of the biggest problems implying this technique is that is not possible to fabricate crystalline thin films with epitaxial or columnar structure and that the density of the material is lower than the one obtained by other technique. High quality films can still be obtained by this process comparing with other techniques and, along with the advantages offered by MOD convinced many researchers to use it in their investigations.
Liquid solution of BTS was prepared by mixing barium isopropoxide [Ba[OCH(CH3)2]2], titanium butoxide [Ti[O(CH2)3CH3]4] tin isopropoxide [Sn[OCH(CH3)2]4] and 1-methoxy-2-propanol supplied by Toshima MGF. CO.LTD.
The Ba(Ti0.85,Sn0.15)O3 (BTS) solution was deposited on Pt(240nm)/Ti(60nm) /SiO2(600nm)/Si substrates by spin-coating at 500 rpm for 5 seconds followed by another 20 seconds at 2200 rpm. This step was performed in enriched N2 atmosphere (1-5 l/min flow) to avoid moisture, because the solution is highly hygroscopic. After spin coating, the film was moved quickly on a hot plate and dried at 250ºC for one minute followed by 10 minutes drying into an oven at the same temperature in air. After drying, the BTS films were pyrolyzed at 450ºC for 10 minutes into an oven in enriched O2 atmosphere (1 l/min
Process flow of the BTS thin films prepared by MOD
TG-DTA analysis results of the BTS MOD-solution
flow). Spin-coating / drying / pyrolyzing sequence was repeated another 4 times before annealing in enriched O2 atmosphere (1 l/min flow) for 10 minutes was performed. The BST15 thin films were annealed at 600ºC, 700ºC, 750ºC or 800ºC. The deposition and heat treatment were repeated 20 times before a final annealing was performed for 20 minutes in O2 enriched atmosphere. The schematic representation of the deposition steps is shown in Figure 2. Differential thermal analysis (DTA) and thermo-gravimetric analysis (TG) (Figure 3) were used to determine the thermal decomposition behavior of the BTS solution and to select the appropriate temperatures for drying and baking. DTA curve shows an endothermic peak at 103ºC corresponding to solvent evaporation point and two exothermic peaks at 350 and 370ºC, temperatures that correspond to precursor decomposition and formation of BTS compound. The TG curve showed that the total mass of the investigated liquid decreases rapidly at the beginning, the solution loosing almost 94% of its mass at 180ºC and slowly loosing more, reaching -97% at 380ºC. The weight loss is insignificant above 380ºC.
According to TG-DTA results, a drying temperature over 180ºC and a baking temperature over 370ºC are necessary. A drying temperature of 250ºC and baking temperature of 450ºC were selected to ensure full solvent evaporation in short time and to minimize as much as possible the stress and defects caused by a further weight reduction during annealing and a rapid complete precursor decomposition and BTS formation.
The thickness of the BTS15 films obtained by this process was about 360nm.
After BTS thin films preparation was completed, Pt/Ti electrodes were formed on the film by RF sputtering to make BTS capacitors. After completion of BTS capacitor fabrication, for films annealed at 700ºC, a post electrode-forming annealing was performed at temperature varying from 200 to 350ºC in air and at 300ºC in high vacuum for 60 minutes.
In order to obtain high quality films suitable for DB-mode of infrared sensing applications (high values of TCD), the BTS thin film properties have been studied for different fabrication conditions and the results were used to optimize the deposition conditions for improved BTS thin films. The influence of annealing temperature and postannealing treatment on physical and electrical properties of the fabricated BTS thin films was investigated aiming an increase in TCD values near room temperature. The temperature of maximum permittivity for the fabricated BTS thin films was found to be near 13ºC.
The annealing effect on the properties of the fabricated BTS thin films has been checked first in order to optimize the fabrication conditions.
XRD patterns of the BTS thin films annealed at different annealing temperatures
In Figure 4, XRD patterns of the films annealed at temperature ranging from 600ºC to 800ºC are showed. The films annealed at 600ºC are still amorphous but for films annealed at 700ºC and higher, crystal structure has been detected. The films have strong (110) peaks suggesting that the crystalline BTS films have a preferential orientation along (110) direction. The other peaks, assignable to a cubic perovskite type structure, are also present but their intensities are much smaller than the intensity of (110) peak. The preferred orientation and intensity ratios among the peaks revealed little distinct differences among these films as a function of annealing temperature. The average grain size was estimated from the half-width of the x-ray diffraction peak using Scherrer’s formula to be in the 33.3 – 50 nm range.
For films fabricated at annealing temperatures of 700, 750 and 800ºC, leakage currents, C-V and temperature dependence of capacity (and through it, the permittivity dependence) were measured and analyzed. Except the temperature dependence of capacity, the other electrical measurements were performed at room temperature, well above the temperature of maximum permittivity.
The leakage current measurements showed that the films annealed at 750ºC have a higher leakage current than films annealed at 700ºC and 800ºC (Figure 5). The reason for this behavior is still not clearly understood. Because films with small leakage currents are desired the films annealed at 750ºC cannot be considered suitable for DB-mode infrared sensing applications. For this reason the attention was focused on the films annealed at 700ºC and 800ºC.
Leakage current for BTS films annealed at different temperatures
The investigations of the temperature influence on the dielectric loss (Figure 6) revealed that the dielectric loss increases with increase in annealing temperature. Moreover, the dielectric loss for films annealed at 800ºC shows large temperature dependence compared with films annealed at 700 and 750ºC. On the other hand, the films annealed at 700ºC have the dielectric loss very little affected by the increase in the annealing temperature.
In Figure 7, temperature dependence of capacitance for films annealed at 700ºC and 800ºC has been plotted. The variation of capacitance for BTS samples annealed at 700ºC is more pronounced than for the samples annealed at 800ºC.
Reviewing the results obtained after physical and electrical properties in becomes clear that annealing at 700ºC is more suitable in obtaining BTS thin films with good properties for DB-mode of infrared sensor applications.
Dielectric loss vs. sample temperature for BTS films annealed at different temperatures
Capacitance vs. sample temperature for BTS films annealed at 7000C and 8000C
The effect of postannealing temperatures on physical and electrical properties of BTS thin films was investigated keeping in mind that the films should be suitable for DB-mode of infrared sensor. The annealing temperature has been set to 700ºC as a result of annealing temperature effect investigations performed earlier. After the top-electrode deposition, a postannealing treatment has been performed at temperatures of 200, 300 and 350ºC in air and at 300ºC, in vacuum for 60 minutes. The results of the investigations made on BTS samples are summarized in Table 1.
Postannealing effect on physical and electrical characteristics of BTS thin films. Leakage densities are given for an applied voltage of 10V
Only some electrical properties are affected by the treatment. Polarization in P-E hysteresis loops is increasing with the increase in postannealing temperature (not shown here). This can be explained considering the fact that a postannealing treatment is improving the metal-ferroelectric interface. The effect of oxygen diffusion during postannealing treatment should not be neglected while considering improvement in polarization. However, as we will show below, increase in polarization due only to improvement in film surface due to reduction in oxygen vacancies by oxygen diffusion from air cannot fully explain the tendency.
Analyzing the results summarized in Table 1 it can be seen that the current leakage of the BTS samples is the most affected by postannealing temperature being smaller for films postannealed at 200ºC. It can be observed that increase in postannealing temperature will not further improve the leakage currents of the samples. Y. Fukuda et al. (Fukuda et al., 1997) reported that, by increasing the postannealing temperature in the case of (Ba,Sr)TiO3 thin films deposited on Pt/SiO2/Si or SrTiO3 substrates, the diffusion of the oxygen from the postannealing atmosphere is decreasing. Our results suggest the same effect by increasing the postannealing temperature because the leakage current, even if it is better than that for as-deposited samples, is increasing by increasing the annealing temperature.
Figure 8 is showing the I-E1/2 characteristics of the leakage current for BTS samples postannealed at 200ºC and 350ºC along leakage current for samples that were not postannealed. The leakage behavior for samples postannealed at 300ºC is not shown to avoid overlay in the graphic because it shows almost the same behavior as samples annealed at 350ºC. It can be seen in the figure that postannealing treatment decreases Schottky leakage currents. The Schottky currents can be described by (Sze, 1981; Fukuda et al., 1998):
where
J-E1/2 characteristics of the leakage current for BTS samples, as-deposited and postannealed at 200ºC and 350ºC (Schottky currents)
In figure 8 it can be observed that the first part of the I-E1/2 characteristics can be plotted with a straight line, suggesting that the leakage is mainly due to Schottky currents. Moreover, the plotted lines seem to be almost parallel to each other. Similar result has been obtained by Fukuda while investigating the effects of postannealing in oxygen ambient on leakage properties of (Ba,Sr)TiO3 thin film capacitors (Fukuda et al., 1998). Because the plotted lines are parallel, all parameters except
Focusing the attention back to table 1, it can be seen that TCD is highest for samples postannealed at 300ºC reaching 5.6% at 25ºC. Even if the leakage behavior for samples postannealed at 300ºC and 350ºC is almost similar, we expect a difference in oxygen vacancy concentration due to different oxygen diffusion coefficients.
In order to understand how postannealing at 300ºC is improving the value of TCD, the postannealing treatment has been performed in air as well as in high vacuum conditions. In this way the effect of presence of oxygen in the postannealing atmosphere can be better understood. Physical and electrical properties (especially leakage current and TCD versus sample temperature) were again investigated but this time the attention has been focused into noticing any particular differences among samples.
Post-annealing after electrode deposition in air or vacuum was found to have little effect on the BTS XRD peaks, indicating that the crystalline structure is not changed after the post-annealing. AFM observation (not shown here) revealed a root-mean-square (RMS) roughness of 1 to 3 nm.
The chemical change induced by the postannealing in films was obtained after XPS investigations (Figure 9). The attention was focused upon the chemical shifts that were clearly visible in the samples. The peaks were carefully calibrated using the Pt peaks and viewing the carbon peaks for confirmation.
XPS spectra for BTS thin films as-deposited and postannealed at 300ºC for 1 hour in vacuum and air.
TCD vs.film temperature for BTS thin films as-deposited and postannealed at 300ºC for 1 hour in vacuum and air
The exact binding energy of an electron depends upon the formal oxidation state of the atom from which it was extracted and local chemical and physical environment. The postannealing after electrode deposition was performed in air as well in vacuum to study the influence of diffused oxygen to the chemical properties of the near-surface layer of the BTS thin films. For postannealed films in vacuum or air, the Ti peaks are shifting towards higher binding energies than Ti peaks for as-deposited films. The presence of O2 in the air can explain why the Ti peaks for the sample postannealed in air are shifting more than the Ti peaks for the sample postannealed in vacuum. Chemically speaking, the presence of O2 in postannealing atmosphere causes oxygen diffusion into the BTS thin films that will be responsible for the reduction in concentration of the oxygen vacancies near the surface, increasing the oxidation state of the Ti, causing the shift of the Ti peaks position towards higher binding energies in XPS investigations.
An important electrical measurement is the investigation of the temperature dependence of the capacitance (i.e. dielectric constant). Figure 10 shows the TCD behavior for BTS thin films as-deposited and postannealed in air and vacuum. The films post-annealed at 300ºC in air have TCD values reaching more than 5.4 %/K at 25ºC and 11 %/K at 20ºC, which is very high compared with similar reported values for TCD. The improvement in TCD values makes the BTS thin film very promising for realizing highly sensitive dielectric-bolometer mode of infrared sensor.
Because of the principle of operation, a dielectric-bolometer mode is expected to offer high sensitivity compared with other detectors (Noda et al., 1999; Balcerak, 1999; Radford et al., 1999; Noda et al., 1999). This aspect, along with other advantages offered, such as chopper free device and low operation voltages are good reasons to consider the DB-mode a good choice in fabricating an infrared sensor.
Following the results obtained for ferroelectric BTS thin films, integration into a simple infrared sensing structure will confirm that the BTS can be considered a good candidate for DB-mode of infrared sensing applications.
Picture view of the infrared sensor cell
In order to investigate what are the sensor capabilities of a structure containing BTS thin film as detecting layer, a simple structure was made, containing a simple capacitance ratio sensor that will sense any capacitance difference between detector and reference capacitors. A picture view of the fabricated structure is shown in Figure11.
Fabrication of the structure on silicon was made with the use of silicon micro machining process. The fabrication steps are shown in Figure 12. Only the detector-capacitor is constructed on a membrane, the reference capacitor will stay on SiO2/Si3N4/SiO2/Si substrate.
Process of infrared sensor fabrication
Detection circuit for infrared measurement
Schematically, an infrared sensing cell can be represented as in Figure 13. A sensing cell is composed of serially connected capacitors. This sensor cell is operating on the principle of sensing the change in the capacitance of the detector-capacitance relative to reference capacitance. Because of the construction, when the sensing cell is exposed to infrared radiation, the temperature at the ferroelectric BTS material site for the detecting capacitor is higher compared with the one for the reference capacitor. Different temperatures are responsible for different dielectric constant values at the detector and reference capacitors that translate into different capacitance values. The variation of the capacitance of the detector-capacitor relative to the value of the capacitance in reference capacitor is detected as a voltage change. Because this voltage signal is very small, amplification is required for the detection.
The infrared response evaluation system is showed schematically in Figure 14. In infrared response evaluation, the temperature of a black body radiator (600ºC to room temperature range) is used as source of infrared rays. The infrared rays were focused with germanium lens so that the radiation will fall mainly on the single element sensor. A function generator was used to apply sinusoidal waves with voltage amplitude of 3V, offset of 1.5V and frequency of 1kHz to both capacitors. An almost 180 degree reversal of the phase was used in the capacitors in order to minimize the output signal. When infrared radiation will fall on the detecting capacitor, heating will cause a change in the value of capacitance. This change will affect the “equilibrium” state in the circuit and a Vout signal will be detected. The output voltage is then amplified through the band-pass filter of 1 kHz for which lock-in amplifier was substituted and observed as an output waveform with an oscilloscope. Furthermore, using the high-speed Fourier transform (FFT) function built in the oscilloscope, the output signal is extracted.
Infrared response evaluation system
The optimization of the DB operation conditions has to be made before making any comment about the sensing properties of the ferroelectric BTS thin films. Running a set of experiments such as DB output voltage behavior at different applied voltages considering the low leakage behavior of the films at low applied voltages or DB output voltage behavior at different applied frequencies are essential in increasing device sensitivity.
Blackbody temperature dependence of DB output as a parameter of the operation amplitude of supply voltage is showed in Figure 15. For the same sensing cell structure and the same applied frequency, DB output signal is increased by increase in applied voltage amplitude.
Blackbody temperature dependence of DB output as a parameter of the applied frequency of supply voltage is shown in Figure 16.
It can be seen that the DB output level increases with decreasing the frequency of the supplied voltage. The reason for this behavior is considered to be the fact that not the entire voltage amplitude is applied to the series capacitor structure while the frequency is increased.
It can be concluded now that the optimal DB operation conditions are:
Larger amplitude of supply voltage. The amplitude should be, however, small enough to ensure small leakage currents through the BTS thin film. 3 to 5 V amplitude for the applied voltage is considered here;
Low operation frequency for the applied voltage. 10 or 100Hz is considered in this experiment.
DB output as a parameter of the operation amplitude of supply voltage
DB output as a parameter of the operation frequency of supply voltage
As a result of optimization, sensing properties of the BTS ferroelectric thin film can be investigated. The output voltage for infrared sensing cells containing BTS thin films as deposited and postannealed at 300ºC in air for 60 minutes is shown in Figure 17.
Output voltage vs. blackbody temperature for sensing cells containing BTS thin films as deposited and postannealed at 300ºC in air
Output voltage for blackbody temperatures below 100ºC for sensing cells containing BTS thin films as deposited and postannealed at 300ºC in air
The importance of postannealing can be clearly seen from this figure. Moreover, a closer look at the response while exposing to the infrared radiations emitted by the black body when its temperature was below 100ºC (Figure 18) revealed that a stable detection of infrared radiation emitted by a blackbody when its temperature was 27ºC was successfully obtained. However the output signal is less than expected because 75% of the incident radiation is reflected by the top electrode; only a maximum of 25% of incident radiation will cause the heating in the sensing cell. Voltage responsivity (Rv) and specific detectivity (D٭) were calculated to be 0.1 KV/W and 3x108 cmHz1/2W, respectively, being in the same range as thin metal oxide film bolometers.
BTS obtained by metal-organic decomposition process can be successfully used as active material in fabrication of DB-mode of infrared sensor. As demonstrated above, temperatures lower than the temperature of a human body can be successfully detected by this type of infrared sensor cell using BTS deposited by metal-organic decomposition process as active material.
The demand of miniaturization and increased functionality in electronic devices trigered the need of finding ways to increase densification of components on electronic boards and 3D packing. There is a need to improve current technologies or develop new ones in order to cope with the problems that arise with miniaturization and 3D packing. The use of high temperatures during fabrication are not desirable since can trigger unwanted chemical reactions, interdiffusion, shrinkage and/or alteration of electrical properties for the component already present on the circuit board. A relatively new deposition method called the Aerosol Deposition (AD) technique based on room temperature impact consolidation (RTIC) phenomena can be a good alternative in film formation at room temperature (Akedo & Lebedev, 1999; Akedo et al., 1999; Akedo & Lebedev, 2001; Akedo, 2004; Akedo, 2006). In this way, the problems linked with relatively high temperatures needed for film formation using the current (more popular) technologies can be avoided and embedding of dense ceramics into low temperature substrate becomes possible.
As mentioned earlier, barium strontium titanate is an extensively investigated ferroelectric material due to its good electrical properties in bulk and thin film form being a leading candidate for applications in many electronic devices. Barium strontium titanate is currently considered as an attractive material in sensing, memory, capacitor and RF and microwave applications (Kirchoefer et al., 2002; Acikel et al., 2002; Hwang et al., 1995; Zhu et al., 2004; Tissot, 2003). But many important issues, such as improving dielectric constant values, dielectric loss and leakage, still need further attention in order to improve film quality and device performance. Regarding the AD-deposited (Ba0.6,Sr0.4)TiO3 (BST) films, there are few reports regarding the film particularities. The logical ways to improve film properties are by tempering with film chemical composition, deposition conditions and post-film-formation treatments, and metallization. However, preliminary results have shown that post-film formation annealing is not helpful to improve the properties of the AD-fabricated BST films (Popovici et al., 2009). The substrate is also playing an important role in improving the AD-fabricated BST film properties since a soft substrate is suitable in ensuring that the films are less stressed (Popovici et al., 2008).
For AD process, powder condition is one of the most important factors since humidity, physical characteristics of the particle and particle aggregation are affecting the deposition rate and film properties.
Below, only the results on the investigation regarding the quality of commercially available (raw) powder used in the AD-deposition and improvement by heat treatments to allow the fabrication of (Ba0.6,Sr0.4)TiO3 (BST60) layers with higher dielectric constants will be discussed due to space constrains in writing this article.
BST60 thick films were grown by the AD technique on Cu substrates using raw and thermally treated powders. To investigate the effect of powder thermal treatment on AD-fabricated BST60 thick films properties, powder from the same lot has been thermally treated for 1 h at 800 or 900ºC in O2 atmosphere.
The AD system used in film fabrication is represented schematically in figure 19. Powder aerosols are formed by oxygen flowing in the vacuum powder chamber at a rate of 4 l/min and transported through connecting tubes to the vacuum deposition chamber where the particle are ejected through the nozzle toward a moving substrate for deposition. A schematic representation of the consolidation process by AD is shown in figure 20. During AD deposition, the particles will suffer a plastic like deformation and fracture upon impact with the substrate. This plastic like deformation and the fracture of the impacting particles are essential to ensure the formation of very dense AD films.
Schematic representation of AD system
Schematics of consolidation process by AD
Before being used in AD, the powder is optimized by ball milling to allow fabrication of high quality films at high deposition rates and with minimum consumption of powder. The average particle size after ball milling should fall within the optimum range (considered to be 0.7-1.4 μm for the BST powder). The thickness of the fabricated BST60 films was around 3 μm and their density was estimated to be in the 92-93% range from the theoretical density, being independent of the powder condition. To examine the electrical properties of the films, Pt/Ti electrodes were deposited by RF sputtering on BST60 thick films to form capacitor structures.
In BST powder synthesis, there are a number of reports that suggest that the presence of BaCO3 in BT and BST powders is difficult to prevent whatever the fabrication route is used (Henningh & Mayr, 1978; Coutures et al., 1992; Hennings & Schreinemacher, 1992; Stockenhuber et al., 1993; Lemoine et al., 1994; Ries et al.,2003). Moreover, there are reports that suggest that BT is thermodynamically unstable in H2O having a pH below 12 (Lencka & Riman, 1993; Abicht et al., 1997; Voltzke et al.,1999). The BST is expected to show a similar problem since it is a BT-based material. The most probable chemical reaction with water is shown below:
The formed solid TiO2 (amorphous) will remain in the outer shell of the initial BT (or BST) particle and will act as a barrier in the further removal of Ba by water (Voltzke et al., 1999). Upon air exposure, Ba(OH)2 will react as follows:
The instability of strontium titanate (STO) material in water is not confirmed, therefore, only, only the instability of Ba2+ ions in H2O is considered here.
Whatever the reasons for the presence of BaCO3 as a secondary phase in BST and BT powders, BaCO3 formation must be controlled to ensure the fabrication of BST or BT films with the desired properties since AD is a room temperature process and post-film-formation thermal treatments at elevated temperatures are not reccomended.
X-ray photoelectron spectroscopy (XPS) has been used to clarify the presence of the secondary phase in the powder and films and the effect of powder annealing. The powder specimens were prepared on Al plate using a commercial double-sided adhesive tape on which the powder adhered. The tape was well covered with powder to avoid the occurrence of tape-related peaks in the XPS spectra. For calibration purpose and to avoid charging due to electron photoemission, a very thin layer of Au was deposited on the surface of the samples by RF sputtering. Six elements were detected on the surface of the investigated samples: C, Au, O, Ba, Sr and Ti. The Au peaks were used to calibrate the XPS profiles.
The XPS profiles of the C 1s peaks of raw powder, the AD-fabricated film obtained from this powder, and powder recovered from the deposition chamber are shown in figure 21. The C 1s peak located near 284.8 eV is commonly attributed to C-C and C-H bonds. The C 1s peak located near 288.45 eV is assumed to be correlated with the C state in CO32- of BaCO3 (Viviani et al, 1999) since the other possible chemical states for carbon, C-O and CO2, should reveal peaks located at binding energies that are higher with approximately 2 eV (Viviani et al, 1999) and 7 eV (Wagner et al.,1979), respectively, than those of the reference C 1s peak. Comparing the relative intensities of the CO32--related C 1s peak (relative to Sr 3p3/2 peak) for the raw powder, AD-fabricated BST60 film, and powder recovered from the deposition chamber it can be concluded that the relative intensity of the carbonate phase is higher in the AD-fabricated film than in the powder.
XPS C1s peak profile for raw and annealed powders
XRD profiles of BST raw and thermally treated powders
XRD profiles of 900ºC treated powder immediately after treatment and after one year
The XRD profiles of the as-received and 800 and 900ºC thermally treated powders show that the crystallinity is retained in all films. However, a closer observation of the XRD pattern near 2theta=24º revealed the presence of an additional peak that can be assigned to the orthorhombic BaCO3 phase (figure 22). Since the concentraton of BaCO3 second phase is high enough to surpass the sensitivity limit of the X-ray diffraction system, it can be also assumed that a peak related to this phase will also appear in XPS results. On this ground, it has been assumed that the BaCO3 second phase will be responsible for the appearance of a relatively high intensity peak in the C 1s XPS peak profile of the BST60 powder, peak that should be located near 289 eV.
This is another reason for linking the peak located at 288.45 eV in C 1s XPS profile to the C state in CO32- of the BaCO3 second phase. It should be notted that for powders thermally treated at 900ºC for 1 h, peaks generated by the presence of the second carbonate phase were not observed in the XRD profile, suggesting that this temperature is suitable for the removal of the secondary phase in the BST60 powders. To further test the BST powder instability against humidity and CO2 in air some treated powder was intentionally placed in atmospheric conditions for 1 year. In figure 23, the XRD patterns near 2theta=24º are shown for freshly treated powder and powder aged in air for 1 year away from dust. The carbonate peak becomes visible again suggesting that humidity and CO2 from air were sufficient to trigger Ba2+ ion removal from BST60 powders and formation of BaCO3 in the outershell of BST particles.
The effect of powder thermal treatment on the physical and electrical properties of the AD-fabricated BST60 films was also analyzed. As shown in figure 24, the dielectric constant of AD-fabricated films using 900ºC treated powders is highest among the investigated films being close to 200 for a wide frequency range. The dielectric loss in all samples was below 0.06 and no marked changes in this parameter were observed. Since the grain size is similar in all the films, the difference in dielectric constant is not due to its dependence on grain size.
Frequency dependence of dielectric constant for AD BST thick films deposited from raw and thermally treated powders
Due to the unique way deposition of films take place in AD, the material in the outershell of the crystalline particles participating in the consolidation process will always be found to form grain boundaries in the as-deposited AD films. The increase in dielectric constant can be correlated with the improvement of the grain boundary regions since, by minimizing the ammount of the secondary phase, the low dielectric constant carbonate phase will be less present at the grain boundary. Moreover, the leakage in AD films is improved by annealing the powder at 900ºC (figure 24).
Leakage of BST films deposited from raw and 900ºC thermally treated powders
For the AD-fabricated BST60 thick films obtained from 900ºC treated powders, the leakage currents stay below 10-7 A/cm2 for applied electric fields up to 500 kV/cm. A reduction in leakage current of one or two orders of magnitude is observed for the AD-fabricated films obtained from 900ºC treated powders as compared with the films fabricated from raw powders. This is another indication that the grain boundaries of the BST60 films were modified following the thermal treatment of the powders at 900ºC prior to deposition. The removal of the secondary phase from the grain boundary regions by thermally treating the powder at 900ºC increases the resistivity of the grain boundary regions, reducing the leakage currents through the grain boundary.
Thermal treatment of commercially available BST powder at 900ºC is a good approach to increase the overall performance of the AD-fabricated BST thick films deposited at room temperature and to make them more attractive for embedded multilayer capacitor applications.
BT-based materials represent a class of materials with a wide range of applications. Here, we showed how substitution in A or B site can make these materials suitable for different applications. Two examples of how BT-based materials can show potential in specific applications are discussed.
Ba(Ti0.85,Sn0.15) (BTS) ferroelectric thin films have been prepared by metal-organic decomposition (MOD) technique. Annealing and postannealing temperatures were optimized to obtain films with suitable electrical properties for application in DB-mode of infrared sensing. Annealing at 700ºC has as the result the minimization of the leakage current and the dielectric loss. Also, the capacitance of a capacitor containing BTS thin film crystallized at this temperature will decrease more rapidly with an increase in film temperature than on a similar capacitor made with BTS thin films annealed at 800ºC. Considering the results, annealing at 700ºCis suitable to fabricate with good properties for application to DB-mode of infrared sensing. Applying a postannealing treatment to the capacitors after top-electrode deposition can improve further the electrical properties of the BTS thin films. It has been found that, postannealing at 300ºC in air for 60 minutes, even if the leakage is higher than in the case of postannealing at 200ºC, will increase the value of the temperature coefficient of dielectric constant (TCD) from 1 %/K to 5.6 %/K at 25ºC comparing with only 1.3 %/K for films postannealed at 200ºC. A closer look on the leakage current behavior on BTS films postannealed in air reveals that an increase in postannealing temperature will reduce the oxygen diffusion from the air into the films that translates as higher leakage currents for samples postannealed at temperatures higher than 200ºC than on the samples postannealed at 200ºC. However these values are still smaller than that of as-deposited BTS thin films. TCD values are higher for samples postannealed at 300ºC suggesting that some degree of oxygen deficiency in the film is needed in order to obtain satisfactory values for TCD. A close investigation regarding the importance of postannealing at 300ºC revealed the important role played by the oxygen vacancies to the value of TCD. Postannealing in air-free environment will not do much improvement to the electrical properties of the film except a relatively small increase in polarization observed in P-E hysteresis loops. On the other hand, postannealing in air will promote oxygen diffusion into the film and, as a result, a change in electrical properties of the dead-layer and a change in the lattice parameters of the crystalline BTS thin films. It can be observed that postannealing at 300ºC for 60 minutes is an important condition in order to fabricate BTS thin films suitable for DB-mode of infrared sensing. The results obtained after BTS film investigations were used in the fabrication of a simple-structures infrared sensing cell. The cell consist in a series of two capacitors, one used as reference capacitor and the other, fabricated on a membrane to reduce the thermal loss, used as detector-capacitor.After optimization of the BD operation mode (application of sinusoidal waves with a voltage amplitude of 3 to 5V and a frequency between 10Hz and 100Hz) sensing properties of the films were revealed. A stable infrared detection was possible even for objects (in this case a black body) heated at temperatures of 27ºC. Good figures-of-merit such as voltage responsivity (Rv) of 0.1 KV/W and specific detectivity (D٭) of 3x108 cmHz1/2W were also calculated making BTS material a strong candidate for application in DB-mode of infrared sensing.
(Ba0.6,Sr0.4)TiO3 (BST60) thick films were fabricated on Cu substrates by Aerosol Deposition (AD) method. The quality of the raw powder has been checked and optimized in order to increase the dielectric constant of the fabricated films without the need of post-film-formation annealing procedure. Carbonate phase has been observed in the raw powders and it was successfully reduced by thermally treating the powder at 900ºC. The AD-fabricated films obtained from the 900ºC treated powder show a dielectric constant of 200 being much higher that the dielectric constant of the AD-films obtained from the as-received powders. The leakage currents in the films fabricated from 900ºC treated powders stay below 10-7 A/cm2 when the applied electric filed is less than 500 kV/cm and it is at least one order of magnitude smaller than for films obtained from as-received powders. The above results indicate that thermally treating the powder at 900ºC is a good way to improve the AD-fabricated BST60 thick films electrical properties. This results represent a step forward in our goal of ceramic fabrication at room temperature aiming integration into embedded multilayered ceramic capacitor structures in electronic devices.
The first author acknowledge the support of Japanese Government Scholarship (Monbukagakusho) program in making possible his research and study at Osaka University.This research has also been partially supported by the NEDO project on “The next generation MEMS (Fine MEMS) project” in Japan.
Chronic obstructive pulmonary disease (COPD) is among the five leading causes of death in developed world [1]. Prevalence of COPD is constantly increasing. COPD has a high impact on patients’ wellbeing, healthcare utilization, and mortality [2] and causes a substantial and increasing economic and social burden [3, 4]. Cigarette smoking is clearly the predominant cause but other environmental agents including biomass fuel and air pollution may play a role as well. Common symptoms of COPD patients are chronic and progressive dyspnea, cough, and sputum production. These symptoms can be disabling and lead to activity limitation and ultimately inability to work and take care of themselves [5]. This vicious circle of inactivity that begins with breathlessness is because of peripheral muscle dysfunction [6], and dynamic hyperinflation [7].
\nFor several decades, treatment of COPD has been focused on smoking cessation, and pharmacological but with ever-increasing literature, intense exercise programs like pulmonary rehabilitation (PR) have become an integral part of management of COPD [8]. PR has been shown to be the most effective non-pharmacological intervention for improving health status in COPD patients and has become a standard of care for these patients [2]. PR and pharmacological therapy are not competitive but rather, must work closely together, if they are to result in a more successful outcome [9].
\nDespite increasing awareness on positive impact of rehabilitation in COPD, it remains underutilized in most countries. Lack of understanding on the benefits of a PR program, in addition to the incremental cost to the management, has hindered the widespread adoption of comprehensive PR for COPD patients [9]. This chapter aims at highlighting the impact of PR on patients with COPD, focusing on the clinical usefulness of PR. We also hope to stimulate primary care and pulmonary physicians to use PR more often.
\nPhysical therapy has been incorporated into the treatment of pulmonary patients as far back as the First World War. Winifred Linton, a British nurse, first felt the need for physical therapy while treating traumatic respiratory complications during the war. Following the war, she entered physical therapy training and began to teach localized breathing exercises to other physical therapists (PTs) and surgeons at the Royal Brompton Hospital in London. A few physical therapists in the United States were instructed in airway clearance techniques and began to use and teach them to patients during the polio epidemic of the 1940s [10, 11]. Rehabilitation programs for patients with COPD have existed for more than three decades and were incorporated into ATS official statement in 1981 [12]. Comprehensive and multidisciplinary approach to the pulmonary rehabilitation programs have remained the key to its success over several years. It involves a team effort from physical therapist, respiratory therapist, nurses, physician and other support staff.
\nPulmonary rehabilitation has been defined as a comprehensive program which is individual patient focused and includes exercise training, education, and behavior change. It has been found to help improve the physical and psychological condition of people with chronic respiratory disease and to promote the long-term adherence to health-enhancing behaviors [13].
\nPulmonary rehabilitation has demonstrated physiological, symptom reducing, psychosocial, and health economic benefits in multiple outcome areas for patients with chronic respiratory diseases [14]. PR is appropriate for most patients with COPD. Improved functional exercise capacity and health-related quality of life has been demonstrated across all grades of COPD severity, although the evidence is strong in patients with moderate to severe disease [15].
\nBeside respiratory symptoms of dyspnea, COPD has been established to have extra-pulmonary manifestations. Some on them involve skeletal muscle dysfunction which results from physical inactivity and systemic inflammation in addition to hypoxemia, undernutrition, oxidative stress and systemic corticosteroid [16, 17].
\nPeripheral muscle dysfunction seen in COPD patients is a result of multitude of pathophysiological changes occurring in the skeletal muscles. Skeletal muscles in COPD patient have decreased oxidative capacity that can lead to early lactic academia [18, 19, 20], decreased muscle fiber volume [21], redistribution of the muscle fiber type (from type 1 to type 2 fibers) [21, 22, 23], and abnormal muscle fiber capillarization [23]. These changes in the structure and functioning of the skeletal muscles can lead to higher concentration of lactate for a given work. This in turn can lead to increased ventilation, resulting in dynamic hyperinflation and overall increased ventilator burden. With muscle dysfunction there is a limitation in the activity and promotion of a sedentary lifestyle. A sedentary lifestyle inevitably leads to social isolation, depression and physical deconditioning. Exacerbations of COPD also promote the reduction of exercise performance, dyspnea, and the loss of Health-related quality of life (HRQoL) [24].
\nPR has no direct impact on lung mechanics or gas exchange [25]. Rather, it optimizes the function of other body systems so that the effect of lung dysfunction is minimized [26]. A comprehensive PR program can help COPD patients gradually improving muscle function by changing muscle biochemical structure. This leads to improved tolerance for higher work load in the patients [27]. PR additionally reduces the central perception of dyspnea and dynamic hyperinflation [28].
\nA usual pulmonary rehabilitation program can range anywhere from 6 weeks to 12 weeks at various centers which incorporate aerobic exercise, education, muscle strengthening etc. Usually patients undergo supervised training 2–3 times a week, for 30–60 minutes in each session. This could include any regimen for endurance training, interval training, resistance/strength training, walking exercises, flexibility, inspiratory muscle training and/or neuromuscular electrical stimulation. The interventions are individualized to maximize personal functional gains.
\nThere are several benefits of PR not limited to improvement in symptoms like dyspnea, exercise tolerance and overall health status in stable patients.
\nPR results in reduction in symptoms of dyspnea and leg discomfort. Patients notice improved limb muscle strength and endurance. Most patients also experience improved functional capacity with more independence in activities of daily living (ADLs) [29]. In a Cochrane review [30] including 23 randomized controlled trials, PR was found to relieve dyspnea, and fatigue, improved emotional function and patient’s sense of control over their condition. All these improvements were large and statistically significant.
\nThere has been increasing interest in physical activity, as inactivity has been linked with reduced survival, poorer quality of life and increased healthcare utilization [31]. In the same Cochrane review as above [30], patients were noted to have improved exercise capacity. Other studies from Griffith’s et al. and Singh et al. have suggested similar findings [32, 33].
\nPR has also been found to reduce unscheduled healthcare visits, COPD exacerbation and hospitalization in some literature [34]. Rubi et al. reported reduction in COPD exacerbation, hospitalization and days of hospitalization in 82 consecutive patients [35]. In fact, there is some literature to suggest reduced hospitalization in patients participating in PR programs immediately after acute exacerbation of COPD (AECOPD) beginning within 1 week of discharge [36].
\nAnxiety and depression affect significantly in COPD patients leading to worse patient centered outcomes. Tselebis et al. conducted study in 101 consecutive patients and noted that psychological morbidity was improved with participation in PR program irrespective of severity of the disease (COPD) [37]. This was confirmed in a meta-analysis of six RCTs which indicated that pulmonary rehabilitation was more effective than standard care for the reduction of anxiety and depression [38].
\nHRQoL was noted to be significantly improved in patients with COPD participating in PR as well [34, 39]. The St. Georges Respiratory Questionnaire Scores were used in a meta-analysis, which showed significant improvement in HRQoL following pulmonary rehabilitation [40]. An early RCT compared pulmonary rehabilitation with education alone and demonstrated that self-efficacy improved in the intervention group [41].
\nCOPD patients have been known to have improved mortality with cessation of smoking. There is some signal that an association exists between completion of PR and survival based on a retrospective analysis involving 1515 patients [42]. But a systematic review conducted of two randomized control trials showed significant survival benefit at 1 year in one trial but no significant benefit with another study at end of 3 years. Neither of the study was powered to really derive the desired outcome [43].
\nPatients with chronic lung condition who have symptomatic shortness of breath limiting their physical activity despite optimal medical management should be considered for pulmonary rehabilitation [44]. Patients with chronic diseases other than lung such as heart failure, musculoskeletal disease have the same benefit form pulmonary rehabilitation as patients with disabling lung conditions like chronic obstructive pulmonary disease, restrictive lung disease, and pulmonary hypertension. Pulmonary rehabilitation can markedly change the course of the disease if provided at an earlier stage of disease. This is due to improved exercise tolerance and physical activity, reduced exacerbations and improved self-efficacy and behavior change after pulmonary rehabilitation. [45]
\nOne of the most important indicator for referral to pulmonary rehabilitation is based on the modified Medical Research Council Breathlessness (mMRC) score (see Table 1) [46]. The mMRC scale is a 0–4 grade scale used to establish levels of perceived respiratory disability. It allows patients to indicate the extent to which their breathlessness affects their mobility [45, 46].
\nGrade | \nLevel of breathlessness with the activities | \n
---|---|
0 | \nNo shortness of breath except on strenuous exercise | \n
1 | \nShort of breath when walking on an incline | \n
2 | \nWalks slower than contemporaries on a level ground because of shortness of breath or has to stop due to breathlessness when walking up at own pace | \n
3 | \nStops for breath when walking 100 m or after a few minutes on level ground | \n
4 | \nToo short of breath to leave the house, or short of breath when dressing and undressing | \n
The modified Medical Research Council Breathlessness (mMRC) score.
It has been strongly recommended that patients with an mMRC dyspnea score of 2–4 who are functionally limited by breathlessness should be referred for pulmonary rehabilitation. However, benefits of pulmonary rehabilitation have also been seen in patients with an mMRC dyspnea score of 1 who are functionally limited by breathlessness. Patients with COPD who have an mMRC score of 4 achieve similar benefits from the pulmonary rehabilitation as those with a lower breathlessness score [47].
\nOther frequent indications for referral to a pulmonary rehabilitation program include poor functional status, physical deconditioning, chronic fatigue, poor health-related quality of life and difficulty performing activities of daily living. Patients who are requiring increased use of medical resources due to frequent exacerbations, hospitalizations and emergency room visits also benefit from pulmonary rehabilitation.
\nCandidates for lung volume reduction surgery for severe emphysema or for lung transplantation are also good candidates for PR [48]. Patients with COPD have shown improvements following a pulmonary rehabilitation program irrespective of their age or gender [49, 50, 51].
\nLevel of functional impairment [47, 52, 53] or disease severity does not affect the benefits seen in COPD patients with pulmonary rehabilitation program [54, 55]. A program of PR may be proposed in stable COPD as well as immediately after COPD exacerbation [56].
\nThere are very few exclusion criteria for a referral to pulmonary rehabilitation, which includes patients with the following conditions [45, 46]:
Unstable cardiovascular disease, uncontrolled diabetes and an ongoing orthopedic illness that will refrain patient from exercising.
Inability to do exercise safely because of any other medical illness like severe arthritis, severe peripheral vascular disease.
Untreated psychiatric illness and cognitive impairment which makes it hard for patients to follow directions are other reasons for not referring a patient to pulmonary rehabilitation.
Lack of motivation is another exclusion criterion for pulmonary rehabilitation.
Adherence to pulmonary rehabilitation program is critical to see the ongoing benefits from the program. However, non- adherence and high dropout rate of 20–30% is reported in the studies listing predictive factors of non-adherence to pulmonary rehabilitation. These factors include [52, 53, 57, 58]:
Even though current smokers obtain the same benefits from pulmonary rehabilitation, smokers generally have poor adherence to pulmonary rehab than ex-smokers. Active smoking status is not an absolute contraindication for pulmonary rehabilitation. Patients are encouraged to undergo smoking cessation prior to pulmonary rehabilitation.
Depression and social isolation.
Lower quadriceps strength.
COPD patients with higher mMRC score and frequent exacerbations.
Long commute to pulmonary rehabilitation and lack of transport.
Cost of pulmonary rehabilitation.
Every patient referred for pulmonary rehabilitation should be thoroughly evaluated prior to initiation of the program. Majority of the patients have a regular pulmonary physician managing the lung disease. As a part of the management, pulmonary physicians refer the patient for pulmonary rehabilitation to supplement the pharmacological treatment. These patients when present to the pulmonary rehabilitation have already undergone an evaluation of symptoms and physical examination. Regardless, it is a good practice to perform a thorough evaluation of patient’s medical problems, laboratory results, social habits and specific medications. This should be accompanied by a comprehensive physical examination with estimation of patient’s functional capacity. In most of the pulmonary rehabilitation program, this assessment is performed by the physical therapists. If a pulmonologist is an integral part of the program, the physician can do this work up.
\nPrior to initiation of the pulmonary rehabilitation program, a careful appraisal of patient’s pulmonary disease and current severity should be done. For COPD patients this will include the duration of their symptoms, current symptomatology, mMRC score [46], smoking history, pulmonary function testing, arterial blood gas analysis, inhaler therapy, oxygen supplementation and non-invasive ventilation prescription. It is imperative that a special attention should be paid to patient’s co morbidities. This is essential as several other medical problems may have impact on patient’s disease course and exercise capacity. These may include obesity, OSA, diabetes, cardiovascular co morbidities, hypertension, osteoarthritis, pulmonary hypertension, peripheral vascular disease and malignancy.
\nA detailed pre rehab assessment enables the physical therapist to devise an individualized treatment plan for the patients. This strategy is particularly helpful for patients with advanced disease, low exercise tolerance, special healthcare needs such as high oxygen requirements, pacemaker or defibrillators, walkers and cane. Information gathered at the beginning of the program will help set realistic individualized goals and alert the provider regarding the possibility of adverse effects.
\nPhysical examination at the beginning of the pulmonary rehabilitation program is centered on measurements of patient’s functional status and capacity to handle additional physical stress. Most relevant for COPD patients will be an examination of muscle wasting, joint mobility, postural deformities, and cardio-respiratory examination. Results of this examination allows physical therapist to gauge individual patient’s tolerance and potential areas of improvement.
\nAn important component of physical examination is nutritional assessment. This commonly includes measurement of weight, height and BMI. Both being underweight and overweight in a COPD patient can be detrimental. Excess weight can lead to extrinsic restriction on lung capacity as well as increased work of breathing. Weight loss and muscle wasting is a poor prognostic factor in COPD patients [59, 60, 61].
\nPertinent respiratory examination in patients with COPD is directed at ability of the patients to clear their respiratory secretions, use of accessory muscles of respiration, breathing pattern, adventitious sounds on auscultation such as wheezing and crepitation. A knowledge of patients’ respiratory status will help develop an educational plan regarding self-management, medication compliance and respiratory muscle training.
\nReduced functional capacity due to physical deconditioning is widespread in COPD patients. This is multifactorial with poor nutritional status, systemic inflammation, cardiovascular comorbidities, postural deformities and osteoporosis [62] Interviewing the patient to ascertain their capacity to perform ADLs, sustained exercise and risk of falls is essential. Several questionnaires have also been used to objectively measure individual patient’s baseline functionality. A few examples include: the Functional Independence Measure (FIM), the Assessment of Motor and Process Skills (AMPS), and a Functional Capacity Evaluation (FCE) [63].
\nApart from questionnaire, various exercise tests can be used to gauge individual patient’s functional capacity. These exercise tests can be done as field walking tests, on bicycle ergometer or on treadmill. In most hospital, simple walk testing can be cost effective and practical. Walk tests are considered more reflective of daily functionality of a COPD patient. Some of the commonly employed walk tests include the 6-minute walk test (6MWT) and the incremental shuttle walk testing. Standardized protocols have been established for performing the 6MWT. If done as per the set protocol, this walk test is highly reproducible and reliable test for both diagnostic and prognostic purposes. In this test, patient walk back and forth on a 30-m distance marked hallway at their own pace for 6 minutes. During the test, distance walked, vital signs, oxygen desaturation, development of dyspnea using a visual analog scale is measured [64]. The incremental shuttle walk test is performed on a 10 m marked course. It is a paced walk test to assess symptom limited maximal exercise capacity. Test is continued until patient develops symptoms of dyspnea or for 20 minutes, whichever occurs first. This is a valid and popular testing in various resource limited clinical settings [45].
\nIf in addition to the functional limitation specific problems are identified by the physical therapists, various other tests may need to be performed. These tests address the muscle weakness, gait disturbances, and include balance testing and sit-to-stand tests [65].
\nAfter an initial assessment, patient is enrolled into a pulmonary rehabilitation program. The basic aim of such a program in any COPD patient is to assist them in performing essential daily activities with independence. Independence comes from reduction in dyspnea and fatigue. COPD patient are inadvertently caught in a downward spiral where dyspnea is leading to inactivity, which in turn leads to physical deconditioning and decreased capacity to handle day-to-day stress. To save the patient from this downward spiral a pulmonary rehabilitation program focuses on improving the cardiorespiratory endurance, muscle strength, body flexibility and respiratory muscle training. With an individualized patient’s clinical analysis and examination, a specific therapy plan can be built for each patient. This plan is intended to establish patient specific goals and focus on areas of functional limitation, which need to improve to achieve those goals. As the COPD patients undergo pulmonary rehabilitation, improvement in their physical deconditioning and exercise capacity needs to be measured and documented. This is achieved by using a variety of parameters, such as quantity of exercise performed or improvement in perception of dyspnea, symptoms, heart rate during exertion. Any changes seen in these parameters will be suggestive of patient’s improved capacity to handle the physical stress. As discussed earlier in the chapter walk tests and questionnaires can provide an objective measure of functional improvement for COPD patients undergoing pulmonary rehabilitation.
\nPhysical exercise training in COPD patients can be delivered in two forms: Continuous high intensity aerobic endurance training or an interval training, which alternates high intensity aerobics with low intensity exercises [66]. Continuous high intensity regimen of endurance training can be administered with constant load or incremental load. It has been shown that high intensity aerobic training (70–80% of peak work rate), will result in maximal improvement in physical fitness by increasing oxygen consumption, delaying anaerobic threshold and decreasing heart rate for a given exercise rate [27, 62, 67, 68, 69].
\nIn patients with advanced COPD and persistent dyspnea a high intensity endurance training is difficult to sustain. These patients can be provided with interval endurance training. In this approach, high intensity aerobic training in short bouts (30–180 s) is alternated with low intensity exercises (leading to a subjective experience of exertion between 4 and 6 on the modified Borg scale) or rest [70, 71, 72, 73, 74].
\nEven though there may be less appreciable gains in aerobic parameters, this training approach has proven to be effective in improving exercise endurance in COPD patients [42, 75]. Interval endurance training leads to lesser degree of pulmonary hyperinflation allowing patients to exercise longer without excessive dyspnea. COPD patients may more easily adapt a lower intensity exercise regimen in their daily life. The choice of regimen is ultimately based on both therapist and patient preference.
\nEndurance training is delivered using various modalities including walking (treadmill or supported ground walking with walker or wheelchair), cycling, rowing, and swimming or modified aerobic dancing. It is recommended to provide this training 3–5 times per week at an intensity aimed at a Borg Dyspnea score of 4–6 (moderate level of exercise) [26, 44, 48, 67, 69, 76, 77, 78, 79]. Exercise sessions can last from 30 to 120 minutes, with at least 30 minutes of continuous aerobic activity, based on each patient’s capacity [26, 46, 79, 80]. General recommendation for the frequency of pulmonary rehabilitation is two supervised exercise sessions a week with third unsupervised session based on the available resources [44, 81, 82]. A minimum of 12 exercise sessions or 4 weeks of rehabilitation program is essential to achieve any improvement in physical fitness. Program length can be increased up to 72 weeks if patient is inclined and insurance coverage is favorable [48, 83, 84]. While shorter (6–8 weeks) pulmonary rehabilitation programs are more cost effective and widespread, longer duration programs have shown sustained beneficial effects. This is mostly due to fact that longer duration programs not only lead to physiological changes but also behavioral changes [85].
\nMore specific for COPD patients it is recommended to check oxyhemoglobin saturation both prior to the start of the exercise and at peak work rate. This will not only help to ascertain the need for oxygen supplementation but also guide both therapist and the patient to know appropriate level to use with different intensity of work. Similarly, a careful attention on patient’s bronchodilator therapy, both long acting and short acting, is essential during the program. Patients may require administration of short acting bronchodilator at the beginning of the exercises or during the workout. For a successful outcome of endurance training it is important that patient gets trained on similar oxygen delivery device that they use at home and are on optimal management of COPD. A stable respiratory function will allow the patients to tolerate higher intensity workout for longer duration.
\nApart from improvement in endurance, COPD patients benefit from increase in their muscle strength [26, 83, 86, 87] . Increased muscle strength provides the patients with an ability to handle the ADLs better, improves their gait and reduce fall risk, thereby making them more independent [88]. A recent meta-analysis investigating different methods of PR in COPD showed greater improvement in HRQoL by adding strength training than endurance training alone [89]. Physiologically improving muscle strength in COPD patients can lead to increase in physical endurance, 6-minute walk distance and maximum oxygen consumption [90, 91]. Strength training is most beneficial if directed at muscles involved in functional living. This involves training muscles in upper and lower extremities as well as the trunk.
\nIt has been well proven that exercise training of the lower extremities leads to significant improvement in ambulatory stamina in COPD patients [42, 67, 92, 93, 94]. This is because lower extremities suffer most from disease-related muscular dystrophy in COPD patients. Additionally increasing lower extremity strength can reduce falls and maintain bone mineral density in COPD patients [45]. General recommendation to improve lower extremity strength is to provide resistance training with 2–4 sets of 10–15 repetitions of each exercise, for 2–3 days per week. Selection of weight for this type of resistance training workout is individualized based on patient’s capacity. Increment in the weight is done gradually once patient is able to accomplish all sets of exercise with a prescribed weight [45]. Lower extremity training can be achieved using walking, bicycling with incremental loads, stair climbing, swimming, weight machines or elastic bands. Choice is driven by available resources at the training site.
\nPatients suffering from COPD who have hyperinflation and flattened diaphragm have limitation in using their upper extremities to perform ADLs. Elevation of arms can result in increased ventilatory and metabolic demands in COPD patients with low respiratory reserves. This is thought to be because some of the upper extremity muscles also serve as accessory muscles of respiration [95, 96, 97]. Majority of the published literature on pulmonary rehabilitation suggests beneficial effect of upper extremity training in COPD patients. Some of the observed benefits of this training include improved upper extremity strength, which is task specific, decreased ventilatory demands and more independence in performing ADLs. Despite these observed benefits, optimal prescription of upper extremity training remains unclear.
\nPhysical therapists have to be mindful that in training the upper extremities, COPD patients may have elevated ventilatory work, asynchronous breathing and more dyspnea for the level of work. It is prudent to start with low resistance and frequent repetitions before gradually increasing the weight [81]. Upper extremity and trunk muscle strength training is achieved by using light weights (dumbbells, elastic bands), weight machines for stronger patients, rowing machines etc. Several of these instruments can also provide aerobic exercise training thereby improving both strength and endurance in the upper extremities.
\nPhysical therapists may provide training of upper and lower extremities on alternate days to improve patient tolerance. Progressive improvement in muscle strength is documented using standardized lifting tests, incremental resistive load tolerated by the patient and increased capacity in performing ADLs efficiently [86].
\nMany COPD patients suffer from modification in the structure of their chest wall due to hyperinflation, hypertrophy of the accessory respiratory muscles and physical inactivity. This further leads to changes in the posture and reduced mobility. To prevent this from happening, COPD patients undergo flexibility training as a part of the pulmonary rehabilitation program.
\nFlexibility exercises lead to improved mobility by increasing joint range of motion, reducing joint stiffness, better posture and increment in vital capacity [45]. Gentle stretching exercises with full body movements, coordinated with breathing techniques are appropriate for COPD patients [65, 98, 99].
\nThis kind of workout teaches the patient the influence of body movements on respiration. Since these exercises are done at a slower pace without any resistive loads, they can be used during warm up or cool down periods of the program. Limited research has been done on adequate duration and intensity of stretching exercises. General recommendation are to perform stretching of major muscle groups in the upper and lower extremities 2–3 days per week at the minimum [100]. Benefits of this training can be measured by documenting reduction in subjective perception of stiffness, reduced incidence of back pain and joint injuries.
\nTo provide a holistic care, every pulmonary rehabilitation program should incorporate patient education. It has been well proven that COPD patients who are well aware about the nature of their disease, its management and long-term implications are able to cope with both the disease and treatment better [101]. Education about the disease empowers the COPD patients to better recognize their symptoms, make lifestyle changes and get involved in the management of the disease. This leads to increased motivation to participate in pulmonary rehabilitation and adhere to the exercise regimen.
\nAt the beginning of the rehabilitation program, individual educational needs of each patient are identified. This is continuously reassessed while the patients are undergoing the rehabilitation program. Instead of a didactic teaching, a patient centered and self-management teaching approach focusing on lifelong behavioral changes are adopted these days [45]. Specifically for COPD patients, a collaborative self-management plan which helps them in an identification of symptoms of onset of an exacerbation, make treatment modification and to communicate early with a healthcare provider, is highly beneficial in the long run [102]. Patient education runs alongside the exercise training. It is meant to supplement the knowledge gaps and instill confidence in the principles of ongoing training. Various topics regarding disease and its management are covered with utilization of the expertise of various specialists.
\nExacerbation of COPD is an additional burden on patient’s already weakened functional capacity. It leads to hospitalization, further inactivity, deterioration of lung capacity and mortality. It may also disrupt any advances the patient may have made in improving their exercise capacity and muscle strength [45, 46]. There is an emerging data suggesting that there is benefit in instituting and/or continuing with pulmonary rehabilitation during hospital admission or within a month of hospital discharge. An early initiation of pulmonary rehabilitation reduces risk of re-hospitalization and improves overall symptoms without any adverse effects [103].
\nA pulmonary rehabilitation program incorporating occupational therapy is important in COPD patients [104, 105]. Occupational therapy assists COPD patients with development of specific strategies to perform ADLs with least expenditure of energy [106]. With conservation of energy expenditure, there is an improvement in subjective perception of breathlessness, increased efficiency in performing daily basic activities, elevated sense of control and better social engagement [104, 105, 106, 107]. Occupational therapy skills even though simple in principle, require a learning process, which is achieved through a multidisciplinary rehabilitation program. There is an ever-increasing evidence that improvement in occupation performance of COPD patients lead to a holistic improvement in their health [108]. Occupational therapist can also instruct COPD patient to use wheeled walking aids, which can result in increased functional autonomy, ventilatory capacity and waling efficiency [109, 110, 111, 112]. Since this therapy has a major impact on social networking of COPD patients, it serves well to involve patient’s family and friends [113].
\nBody composition in COPD patients may change as the disease severity progresses. While obesity predominates in the milder stages of the disease, patients with advanced disease and emphysema tend to be underweight and have generalized muscle wasting [114, 115]. Factors other than the lung disease itself, which can lead to this shift, includes inactivity, systemic inflammation, osteoporosis and glucocorticoids use. Studies have shown an increase in mortality in COPD patients who are underweight, independent of their disease severity [116, 117]. These patients with decreased fat free mass have higher limitation to exercise tolerance and thereby reported a decreased HRQoL status in comparison to COPD patients with normal weight [118, 119, 120, 121]. Various studies have shown a survival benefit with weight gain as low as 2 kg or by increase in one body mass index unit [116, 117]. This is why nutritional education are particularly essential in rehabilitation of COPD patients.
\nEvery pulmonary rehabilitation program should include nutritional screening with measurement of BMI at the least. A more comprehensive program may also include fat free mass estimate using skinfold anthropometry or bioimpedance analysis. Estimation of osteoporosis can be done using dual energy X-ray absorptiometry (DEXA) scanning. Improvement of nutritional status requires a multi-pronged approach with utilization of both physiologic and pharmacological interventions. Endurance and strength training as described previously in this chapter can improve muscle mass as well as bone strength. Nutritional interventions include adding nutritional supplementation to patient’s diet with emphasis on adequate protein intake to maintain or restore lean body mass. Patients who are unable to eat large meals due to dyspnea can switch to frequent small meals. It has been shown that a 6-month intervention involving dietary counseling, nutritional supplementation and positive reinforcement led to a significant weight gain in advanced COPD patients [60].
\nMany COPD patients who are referred to pulmonary rehabilitation suffer from depression and anxiety [45, 122]. Recent studies have estimated prevalence of depressed mood in about 45% and anxiety in 32% of patients with moderate to advanced COPD [123, 124, 125]. Dyspnea on exertion leads to fear and anxiety anytime a COPD patient has to exercise. This severely limits their social interaction and eventually leads to depression. COPD patients can suffer from hopelessness, sense of isolation and lack of motivation. It is essential to assess the presence of depressed mood during initial evaluation in a pulmonary rehabilitation program. Family and caregiver involvement is advisable to assess the social support system for the patient.
\nIdentifying the mood disorders and deficit in the social support is an integral part of the program [114]. Patients in need can be provided with psychological and social support, which works to elevate mood, positive thinking and adaptive behavior towards disease and its management. This also improves the compliance with the pulmonary rehabilitation program. Psychological support can be provided by the physical therapist but often require a psychologist or a psychiatrist involvement.
\nVarious models of PR have been adopted worldwide. An outpatient or hospital based-outpatient setting is the most widely used model to deliver PR to COPD patient in the developed countries [126]. Current body of evidence regarding effectiveness of PR in COPD patients is based on this model. In recent years an alternative model where the site of delivery of PR is at home has been studied. Home based PR setting provides the benefit of exercise training in a familiar setting to a larger patient population. Specifically for patients with severe COPD dependent on long term oxygen therapy, this model of PR has been shown to be both safe and effective [127, 128]. While home based PR model offers convenience, it lacks the group dynamics which an outpatient model can offer. Group therapy leads to socialization, mood elevation and positive reinforcement. Additionally a home based program does not have a multidisciplinary and comprehensive structure of a hospital based outpatient setting. At the present time, choice of location of PR is dependent on patient preference, disease severity and regional availability of resources.
\nSeveral COPD patients with advanced lung disease who are bed bound or wheelchair bound are unable to participate in a conventional pulmonary rehabilitation program. To help these patients, a new modality of transcutaneous neuromuscular electrical stimulation (NMES) has been devised recently [129, 130, 131]. This technology involves application of low amplitude electric current via electrodes transcutaneously to the targeted muscle groups by depolarizing motor neurons. Low intensity electric current (10–100 mA) is delivered at stimulation frequencies between 8 and 120 Hz for duration of 250–400 ms. Although no large RCTs are available, a recent meta-analysis did report improvement in quadriceps strength and exercise capacity with NMES. Unfortunately, no significant improvement in HRQoL in moderate to severe COPD was seen [132]. Apart from debilitated COPD patients, this technology has been recommended for use during COPD exacerbation, as it has low impact on ventilation, heart rate and dyspnea [133, 134].
\nA pulmonary rehabilitation programs for COPD patients usually includes respiratory muscle training. The goal of this training is to improve the abnormal breathing pattern, which may result due to increased work of breathing, chest wall changes and poor breathing habits in COPD patients [135, 136, 137, 138]. The most commonly applied approach is through the endurance and strength training. [26]. Exercise training can lead to increase in minute ventilation, which leads to an increase in work of breathing. Constant controlled aerobic exercises of upper and lower extremities can lead to a recurrent stimulation to respiratory muscles. This helps the COPD patients to modify their breathing patterns on a day-to-day basis as well as be better prepared for an exacerbation.
\nApart from exercise training, specific breathing exercises such as diaphragmatic breathing, paced breathing with exercises and pursed lip breathing has been proven to be beneficial in COPD patients. Diaphragm, which is the main inspiratory muscle, is flattened and ineffective in patients with hyperinflated lungs. This puts these patients at a mechanical disadvantage to adequately maintain and increase their minute ventilation. COPD patients who undergo the training to improve the coordination of their diaphragmatic muscle tend to fare better overall [139].
\nMany patients with emphysema self-discover the method of purse lip breathing for faster recovery from shortness of breath post exercise. Other patients can be instructed regarding this method. It helps patients to increase alveolar ventilation, tidal volume and CO2 removal. It also leads to slow expiratory flow and decreased respiratory rate [140]. Using the same principle, respiratory muscles can be trained by using resistive breathing devices. This can be particularly useful in patients who continue to have dyspnea despite optimal medical management.
\nAdditionally COPD patients specifically with chronic bronchitis occasionally have ineffectual cough leading to difficulty in respiratory secretion clearance. Instructions on special coughing techniques (huffing, autogenic drainage) combined with oscillating expiratory breathing devices (Acapella, In-exsufflator) can prove effective [141]. Patients can be instructed to perform daily chest physiotherapy to assist in respiratory secretion clearance through postural drainage techniques [142]. A meta-analysis of 32 studies focusing on respiratory muscle training showed that it leads to improvement in respiratory muscle strength, exercise capacity and perception of exertional dyspnea [143].
\nThe beneficial effects of a comprehensive pulmonary rehabilitation program are not sustained beyond 12 months [32, 42, 144, 145]. On the other hand, repeating a pulmonary rehabilitation programs has not been found to be an effective treatment option [146]. Considering this, it is challenging to maintain the changes made in physical activity and lifestyle due to a pulmonary rehabilitation. Although there is a lack of data on maintenance programs, some centers do provide these in the hope to achieve prolonged benefits gathered in a successful rehabilitation program. There are no set guidelines to establish an optimal strategy for providing maintenance pulmonary rehabilitation. Additionally other factors such as lack of transportation to the PR center, disruption of daily life routine, absence of family support, perception regarding gains from the PR program, have impact on patient’s participation in the post PR programs. A recent multicenter RCT studying the long term (3 year) maintenance program after PR in severe COPD patients, showed a sustained beneficial effect on BODE index and 6MWD at 24 months. Although, the effect vanished beyond 2 years as at end of study only 66% of COPD patients were still adherent with the maintenance program [147].
\nVarious methods adopted to provide therapy beyond a comprehensive program include weekly telephone contacts, home exercise training with or without weekly-supervised outpatient sessions and recurrent PR program [146, 148, 149, 150, 151]. A recent meta-analysis analyzing post-PR exercise program in COPD patients suggested that such a program even though effective in maintaining a good exercise capacity with the 6 months of PR, loses its benefit beyond 1 year and has no impact on HRQoL [152]. The patient population and the interventions used were variable and results of this study need to be interpreted cautiously.
\nSince the structure of the most effective maintenance program remains elusive, it is important at this time to encourage the COPD patients to continue with healthy lifestyle changes. This can be achieved by a concerted effort of the PR staff, family members, and patients’ healthcare team. Those COPD patients who continue with the exercise routine and lifestyle changes they had learnt in the PR program tend to accumulate gains in physical endurance and psychological functioning [153].
\nPulmonary rehabilitation has a major role in the management of patients with chronic lung conditions especially COPD. The need for more convenient and efficient programs using new technology would be beneficial for patients. Tele-rehabilitation to deliver rehabilitation services over telemedicine using internet or phone can provides services to patients who live in remote areas without access to transportation. Tele-rehabilitation allows video conferencing between a central control unit and a patient at home. This will also deliver health services to patients with disability who cannot travel long distances for rehabilitation programs. Both mobile phones and video conferencing have used in few studies deliver rehabilitation services. The studies have demonstrated good compliance, decrease in exacerbations and hospitalizations, improved exercise capacity and quality of life [154, 155]. Benefits of telemonitoring in COPD patients have been described in a systemic review that showed decrease in hospitalizations and emergency room visits using telephone support for telerehabilitation [156].
\nA comprehensive multimodality pulmonary rehabilitation program is becoming an essential part of the management of COPD patients. It is not only cost effective but also scientifically proven to improve patients’ symptoms and functionality. With a gradual increase in daily activity, COPD patients are able to achieve higher HRQoL compared to pharmacotherapy alone. Despite these proven benefits, widespread utilization of PR remains poor. Multiple factors, including; physician unfamiliarity of benefits of PR, patient compliance with the exercise regimen and insurance coverage contribute to this gap. With the increasing prevalence of COPD worldwide, a safe and effective option like PR needs to be actively promoted and utilized.
\nApart from standardized exercise regimens and strength training, the emphasis of an effective PR program is on behavioral modification. This result in long lasting, positive changes on the disease course. In addition, empowering the COPD patients by educating them about disease, smoking cessation and nutrition is a crucial step in the right direction. Development of home based or telerehabilitation services may assist in reducing the disparity in access to PR for many more COPD patients.
\nAuthors declare no conflicts of interest.
\n chronic obstructive pulmonary disease acute exacerbation of chronic obstructive pulmonary disease pulmonary rehabilitation health-related quality of life randomized controlled trial neuromuscular electrical stimulation activities of daily living modified Medical Research Council 6 minute walk test functional independence measure assessment of motor and process skills functional capacity evaluation dual energy X-ray absorptiometry body mass index, airflow obstruction, dyspnea and exercise capacity
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I received a B.Eng. degree in Computer Engineering with First Class Honors in 2008 from Prince of Songkla University, Songkhla, Thailand, where I received a Ph.D. degree in Electrical Engineering. My research interests are primarily in the area of biomedical signal processing and classification notably EMG (electromyography signal), EOG (electrooculography signal), and EEG (electroencephalography signal), image analysis notably breast cancer analysis and optical coherence tomography, and rehabilitation engineering. I became a student member of IEEE in 2008. During October 2011-March 2012, I had worked at School of Computer Science and Electronic Engineering, University of Essex, Colchester, Essex, United Kingdom. In addition, during a B.Eng. I had been a visiting research student at Faculty of Computer Science, University of Murcia, Murcia, Spain for three months.\n\nI have published over 40 papers during 5 years in refereed journals, books, and conference proceedings in the areas of electro-physiological signals processing and classification, notably EMG and EOG signals, fractal analysis, wavelet analysis, texture analysis, feature extraction and machine learning algorithms, and assistive and rehabilitative devices. I have several computer programming language certificates, i.e. Sun Certified Programmer for the Java 2 Platform 1.4 (SCJP), Microsoft Certified Professional Developer, Web Developer (MCPD), Microsoft Certified Technology Specialist, .NET Framework 2.0 Web (MCTS). I am a Reviewer for several refereed journals and international conferences, such as IEEE Transactions on Biomedical Engineering, IEEE Transactions on Industrial Electronics, Optic Letters, Measurement Science Review, and also a member of the International Advisory Committee for 2012 IEEE Business Engineering and Industrial Applications and 2012 IEEE Symposium on Business, Engineering and Industrial Applications.",institutionString:null,institution:{name:"Joseph Fourier University",country:{name:"France"}}},{id:"55578",title:"Dr.",name:"Antonio",middleName:null,surname:"Jurado-Navas",slug:"antonio-jurado-navas",fullName:"Antonio Jurado-Navas",position:null,profilePictureURL:"https://mts.intechopen.com/storage/users/55578/images/4574_n.png",biography:"Antonio Jurado-Navas received the M.S. degree (2002) and the Ph.D. degree (2009) in Telecommunication Engineering, both from the University of Málaga (Spain). He first worked as a consultant at Vodafone-Spain. 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