Laryngeal Examination with Laryngeal Mirror and Laryngoscopy

Abstract

The management of all laryngeal pathologies begin with a simple and traditional examination with laryngeal mirror. Even though the use of mirror is invaluable, the image is often distorted and misleading in seven different ways. Direct laryngoscopy is a sermon on relaxation and does not require any local or general anesthesia in both children and adults. The greatest advantage of direct laryngoscopy is the presence of oblique illumination. This chapter deals with the different angulations of laryngeal mirrors and its seven drawbacks in detail. This also provides a detailed explanation of direct laryngoscopy technique in children and adults with its axioms and clinical application.

1. Introduction

Laryngeal mirror was first discovered by Professor Manuel Gustave Garcia who was a singer, teacher and composer by profession. He initially used a dentist’s mirror and sunlight to visualize the larynx to demonstrate the physiology of vocal cords [1]. Later, this technique was used by Ludwig Türck who is a neurologist cum laryngologist. As he was largely unsuccessful, the attempts were then carried out by Dr. Johann Nepomuk Czermak, a physiologist. He made some modifications by using an artificial light source and a concave ophthalmologist’s mirror to successfully visualize the larynx. He thus claims to be the first non-laryngologist to visualize a living larynx [2].

Laryngeal mirror is made of stainless steel with a length of 7–10 inch, mirror diameter of 3–8 mm and thickness of 10 mm. An ideal mirror should be angulated to visualize the larynx precisely. The different degrees of angulation can be 30, 45 or 60 degrees. Of these, 45 degree angulation is found to be the most suitable for our clinical use. This angulation can prevent gag reflex and discomfort to the patient as well as provide us with a better picture of larynx. Individuals with short neck may require more angulation.

This can be facilitated by the future development of malleable handles for easy alteration of angulation according to the patient needs.

1.1 Examination of larynx with laryngeal mirror

Position of the patient: The patient should sit back on the chair and head is leaned forwards with flexion of neck and extension of head.

Left index finger is then used to push the upper lip upwards away from the field. Grab the protruded tongue between thumb and middle finger. Rest the little finger on the chin. Defog the mirror using savlon (Chlorhexidine gluconate and cetrimide)/warm water. Introduce the mirror inside after checking the temperature. Push the uvula backwards with the mirror and visualize the epiglottis. The glottis will appear black as it is not illuminated. Make a slight tilt with the mirror to visualize the entire larynx (Figure 1).

Figure 1.

Laryngeal view with mirror.

The training for laryngeal examination using a mirror can be made possible with the help of a laryngeal model. The laryngeal model can be made using acrylic sheeting, cardboard or plywood. Such training of students using artificial models was found to be very helpful for easy diagnosis and better understanding of anatomy [3].

The main advantage of mirror laryngoscopy when compared to endoscopic examination is the 3D image visualized via mirror, thereby avoiding any chance of missing early lesions of larynx especially in vestibule or ventricle where the mucosa may be intact. Other advantages are mirror is inexpensive, easy to use and less time consuming.

A prospective randomized crossover trial was conducted by Dunklebarger et al. to compare video rigid laryngeal endoscopy and laryngeal mirror for examination of larynx in 43 patients [4]. All patients were subjected to single attempt with both methods in alternating order without any topical anesthetics. Each patient was asked to rate the level of comfort and gagging from 1 to 10 for each technique (1 indicates no discomfort/gagging and 10 indicates severe discomfort/gagging). Patients were also asked if they found the video recording of examination useful and which technique they preferred. The examiner also checked the level of extend of examination with each technique and recorded it from a scale of 1 to 6 with 6 indicating complete visualization. The study concluded that examination with 4 mm 30 degree rigid endoscope was better than mirror examination in terms of comfort and extend of visualization. Majority of the patients also preferred rigid endoscopy and found the video recording useful.

Barker et al. conducted a study to compare the success rate and diagnostic accuracy between laryngeal mirror and rigid rod examination of larynx [5]. Success rate with indirect laryngoscopy was 52% whereas, that of rigid rod examination was 83%. The study concluded that laryngeal mirror is an useful screening tool, but rigid rod adds more diagnostic accuracy.

In the study conducted by Grabas et al. to determine the relevance of laryngeal mirror in the examination of larynx and nose, 82% of success rate was found with laryngeal examination [6].

1.2 Disadvantages of laryngeal mirror

The image seen in laryngeal mirror can mislead us in seven different ways.

Even though the plain mirror used in the instrument is round in shape, the image appears to be oval. This will cause a reduction in the anteroposterior dimension or along the vertical axis. As a result of this distortion, the cords appear shorter by about one third of its actual length but its transverse diameter remains the same.

Mirror produces an inverted image. i.e. left cord remains on left side of the patient but anterior commissure is seen posteriorly.

Mirror image can alter the depth perception. Vocal cords appear to be 1–2 cm away from the mirror. But the actual distance is around 6 cm.

Mirror image can cause distortion such that a small vocal cord lesion may appear much posterior than its actual position.

Overhanging ventricular band may be misinterpreted as outer border of vocal cord.

Anterior commissure may be hidden due to the overhanging epiglottis.

Ventricle may be hidden due to the overhanging ventricular band.

Hence, it is quite clear that mirror laryngoscopy when performed by an experienced doctor is always worthy when compared to the other techniques. This technique will never become a lost art in the era of modern medicine even though it has a few demerits [7].

2. Direct laryngoscopy

The first laryngoscope was described by Bozzini in 1805, but its usage was first reported only in 1852 [8]. Since then, a wide range of modifications were introduced and different types of laryngeal blades were made. Even then, the use of rigid laryngoscope, indirect laryngoscope, flexible laryngoscope and video laryngoscope remains fundamental to all ENT surgeons worldwide. This can be attributed to its ease of use, low cost, better visualization with less patient discomfort and complications and easy availability. A laryngoscope has got a handle, blade and a light source. The light source can be diode emitting or fiberoptic light source.

Suspension laryngoscopy with rigid laryngoscope is often used in laryngeal examination for diagnostic and therapeutic purpose. Direct laryngoscopy (rigid or flexible) can be used for phonosurgeries like excision of vocal cord cyst, polyp, excision/biopsy of laryngeal growth, thyroplasty, percutaneous tracheostomy or laryngeal reinnervation surgeries. Direct laryngoscope helps in providing the anatomic and pathologic details in its original form, color and relationship. The main advantage is the provision of oblique illumination due to the presence of distal source of light on its one end. The color should always be adjusted to the same intensity to avoid mucosal blanching due to over illumination. The only absolute contraindication to direct laryngoscopy is disease of cervical spine other than uncontrolled systemic illness.

Video laryngoscope provides a superior view than direct laryngoscope. Numerous types are commercially available in market today. The main disadvantage it that it has a blind spot creates when endotracheal tube is inserted. But its widespread use by surgeons can be attributed to its robust and ease of use with minimal set up time and short learning curve. American Society of Anesthesiologists has added video laryngoscopes to the practice guidelines in management of difficult airways [9].

2.1 Anesthesia

No anesthetic, local or general, is ideally required in both adults and children to perform laryngoscopy if the surgeon is skilled and the teamwork is well coordinated. For this, patient should be relaxed completely or else, examination will be difficult. If required, 10% lignocaine spray can be used as local analgesic. One puff of 10% lignocaine contains 10 mg and 1 ml contains 100 mg of lignocaine. Two to three puffs should be sprayed to the base of the faucal pillar and pharyngeal wall and wait for few minutes for the effect. In older days, cocaine drops were frequently used for anesthetic effect.

2.2 Premedication

When performed under local anesthesia, premedication is highly efficient. 1 ampule of Phenergan or pethidine 25 mg can be given as IM or IV along with IV atropine or glycopyrrolate to reduce the secretions. Atropine 0.6 mg or Glycopyrolate 0.01 mg/kg is the dosage which should be given 10 minutes prior to the procedure.

2.3 Technique

Position of the patient: “sniffing the morning air” position or flexion of neck and extension of head. This is attained by making the patient to lie down in supine position with head raised 10 cm above the body level using a head pillow.

Steps of introducing a laryngoscope:

Retract the upper lip using the right index finger.

Introduce the scope along the right side of anterior two thirds of tongue.

Once the posterior third of tongue is reached, push the scope towards the midline and visualize the epiglottis.

Push the scope towards the posterior pharyngeal wall and insert posterior to the epiglottis to 1 cm down into the larynx (Figure 2).

Figure 2.

Examination with direct laryngoscope.

When performed under local anesthesia, often larynx will be in spasm which is not seen with general anesthesia.

If anterior commissure is not seen, head elevation can be increased or press over the thyroid cartilage externally with the index finger.

Visualize the entire larynx and then while pulling the scope out, check for hypopharyngeal region.

Structures to visualize while performing direct laryngoscopy.

• Tongue

• Base of tongue

• Pharyngeal wall

• Epiglottis

• Vallecula

• Glossoepiglottic fold

• False vocal cord

• Anterior commissure

• Posterior commissure

• Ventricle

• Subglottis

• Anterior wall of trachea

• Arytenoids

• Aryepiglottic fold

• Pyriform fossa

• Movement of vocal cord and arytenoids

2.4 Axioms of direct laryngoscopy

Laryngoscope should always be held in left hand.

Surgeon’s right index finger is used to retract the patient’s upper lip.

Maintain the right patient position with head in midline and flexed only at atlanto-occipital joint.

Laryngoscope should be introduced along the right side of tongue. When the posterior third of tongue is reached, scope should be directed towards the midline. Do not proceed into the larynx without visualizing the epiglottis.

Care should be taken not to insert the scope deeply or else this may hide the epiglottis.

Even after visualizing epiglottis, scope should not be inserted too deeply.

Laryngeal exposure is obtained by lifting forward the epiglottis.

Do not mistake aryepiglottic fold for epiglottis.

If the laryngoscope is long, secretions may tickle down the trachea causing cough. This should be avoided by suctioning adequately.

In children, cartilage is more flexible and larynx will be seen only with a deep breath.

2.5 Advantages

Cords will appear longer than it seemed in the mirror and may not be pearly white in appearance.

True depth perception.

Ventricular bands appear as folds rather than lumps.

Video laryngoscopy is better than direct laryngoscope for glottis visualization and airway assessment/intubation [10, 11]. Whereas, in the systematic review and meta-analysis conducted by Savino et al. states that in physicians with adequate experience with DL, VDL did not contribute to any additional success and may even lead to worsening experience. However, in nonphysician intubators with less DL experience, VDL will provide more benefit [12].

The study conducted by Schild et al. showed that use of an hyperangulated video laryngoscope with usage of modified flexible instruments can be cost effective and minimally invasive alternative in cases of difficult laryngeal exposure [13].

In a study conducted by Boles et al., flexible distal chip laryngoscopy was compared with rigid telescopic laryngoscopy in terms of image quality and diagnostic ability in 18 patients [14]. All 18 adult patients were subjected to both the techniques and the video recorded were analyzed to find the statistical significance in the parameters. The study concluded that rigid laryngoscopy was superior in image quality in terms of color fidelity, resolution and vascularization with better visualization of abnormalities.

A randomized crossover study to compare the patient experience between rigid and flexible laryngoscopy was conducted by Clark et al. in adult patients [15]. They also concluded that flexible scopy was associated with more discomfort and pain than rigid laryngoscopy.

A study was conducted by Swapna et al. to compare the difference in the assessment of posterior glottis chink between rigid laryngoscope and flexible nasopharyngolaryngoscope [16]. 108 patients were subjected to both the techniques of laryngeal examination and posterior glottis chink score was assessed. Score 0 being closed glottis and score four being most open glottis. The study concluded that females had higher posterior glottis chink score and rigid laryngoscope was more efficient in assessing the posterior glottis chink, but the difference was not very significant.

In contrary to this, a retrospective study was conducted by Omokanye et al. to determine the diagnostic efficacy of flexible laryngoscope in 360 patients and was compared with DL. The results showed that the diagnostic accuracy was comparable to DL and is more statistically significant when compared to the above mentioned studies [17]. Thus, the usage of flexible laryngoscopy in OPD setting and DL in theater setting with anesthesia is more reasonable. Flexible laryngoscopy is a simple, safe and cost effective procedure which can be performed with simple head extension, sniffing position or sitting position [18].

A comparative study between rigid and flexible fiberoptic laryngoscope was done by Handler to examine the pediatric larynx [19]. Flexible fiberoptic laryngoscope was chosen as the preferred technique to examine airway dynamics. Rigid laryngoscope was preferred in cases of laryngeal or tracheal surgery. This was due to the ease of use and better image perception as a result of magnification. Hence it is clear from the above mentioned studies that flexible laryngoscope is easy to use and provides good image perception and will be a better option than rigid laryngoscope in OPD settings. Yet, more studies with larger sample size have to be conducted to prove its efficacy.

2.6 Disadvantages

Direct laryngoscopy is an essential tool for phonosurgery. But several parameters can limit its use by restricting the visibility. These include short and stiff neck, obesity, retrognathia, macroglossia and cervical spine pathology limiting neck extension. This can even hinder the process of intubation. The incidence of DLE and difficult intubation is around 1–4% [20]. Hence, the usage of direct laryngoscope in OPD setting without anesthesia is obsolete and is replaced by flexible laryngoscope.

2.7 Complications

Excess application of force while inserting the scope can damage the cartilages or may cause mucosal injury leading to bleeding. Bleeding can in turn obscure the view.

Laryngospasm is another complication if not performed under sufficient anesthesia or due to excess manipulation.

If the correct size of scope is not used, complete visualization of larynx may not be possible.

Resting the scope on the upper jaw or tooth can lead to dental damage and hence should be avoided.

There are different types of rigid laryngoscopes and suspension laryngoscope.

Rigid endoscope can be of different angulations: 45 degree, 70 degree, 90 degree, 110 degree. Of these, 70 degree scope is commonly used.

Color codes for these endoscopes are:

• 0 degree—Green.

• 30 degree—Red.

• 45 degree—Black.

• 70 degree—Yellow.

• 90 degree—Blue.

• 110 degree—Grey.

The different types of suspension laryngoscopes include:

1. Vaughn.

2. Zeitel.

3. Kleinsasser.

4. Bercy-Ward.

5. Bouchayer.

6. Lindholm.

Among these, Vaughn’s and Zeitel’s is preferred for glottic and anterior commissure exposure as it has a triangular distal opening.

2.8 Clinical applications

Vocal fold surgery

• Mucosal and submucosal excision of lesions

• Stripping of vocal folds

• Lysis of synechiae and adhesions

• Vocal fold medialization/augmentation

Foreign body removal.

Laryngeal framework surgery.

Laryngotracheal stenosis—Stent/Keel placement.

Percutaneous tracheostomy.

Assists Intubation.

Diagnosis and treatment of Hypopharyngeal lesions.

Zenkers diverticulum.

3. Conclusions

Rigid direct laryngoscopy in an OPD setting without LA or GA is out of favor in the present context. Instead, it is being replaced by flexible video laryngoscope in an OPD setting, which is more compatible for the patient and gives excellent magnified images which can be photographed or videorecorded for documentation and teaching. Rigid laryngoscope with angulated and self-expanding blades are reserved for microlaryngeal surgical procedures. The only disadvantage of all video endoscopes compared to laryngeal mirror is the lack of 3D perception i.e., lack of depth perception. This can lead to failure to diagnose certain laryngeal lesions which can be easily picked up using a laryngeal mirror. Hence, laryngeal mirror will always serve to be an invaluable instrument for ENT surgeons.

Acknowledgments

We are grateful to our institution and colleagues for providing us with all the support.

Conflict of interest

The authors declare no conflict of interest.

Funding

No funding applicable.

Notes/thanks/other declarations

Nil.

Appendices and nomenclature

Nil.

Abbreviations

DLE	Direct laryngeal endoscopy
DL	Direct laryngoscopy.
VDL	Video direct laryngoscopy.