The American Society of Anesthesiologists Physical Status (ASA PS) classification has long been used as a ranking system that quantifies patient health before anaesthesia and surgery. When initially developed, the ASA PS intended application was purely statistical. However, nowadays it is commonly used by surgical specialties to determine a patient’s likelihood of developing postoperative complications, despite studies reporting scoring method subjectivity and inconsistencies among anaesthesiologists in assigning these scores. Over the years, the ASA PS classifications have undergone many changes and modifications to address its limitations. There are a few points to be discussed if all shortcomings are to be treated and interobserver variability is to be limited.
Part of the book: Surgical Recovery
Although medical services in aviation have evolved over years based on our understanding of physiology, advancement in monitoring technology but airway management was only recently studied with a focus on space environment. The barometric pressure of ambient air declines as altitude increases, while the volume of air in a confined space will increase according to Boyle law, and therefore oxygen concentration remains at a constant 21%. Altitude sensitive equipment includes endotracheal and tracheostomy cuffs, pneumatic anti shock garments, air splints, colostomy bags, Foley catheters, orogastric and nasogastric tubes, ventilators, invasive monitors, and intra-aortic balloon pumps. The microgravity reduces the body compensation capacity for hemorrhage, while the redistribution of the blood can affect intubation by causing facial edema. Another change is the decreased gastric emptying during aviation. Acute respiratory failure, hypoxemia or inadequate ventilation and protection of the airway in a patient with impaired consciousness are common indications for advanced airway management in aviation. Airway management requires adequate training to maintain excellent medical care during aviation. Tracheal intubation using laryngoscopy would be difficult in microgravity, since the force exerted by the laryngoscope causes the head and neck move out of the field of vision by lever effect exerted on the head and generated through the laryngoscope blade by hand generating a lack of stability, resulting in the difficulty to insert the tracheal tube. While on the ground with the help of gravity, an adequate positioning of the patient is facilitated to achieve alignment of the laryngeal, pharyngeal and oral axes, which is known as sniffing position that allows visualization of the vocal cords and supraglottic structures allowing the introduction of an endotracheal tube.
Part of the book: Special Considerations in Human Airway Management