Laryngeal Cuff Force Application Modeling During Air Medical Evacuation Simulation

Abstract

Endotracheal tubes are intended to protect the airway and assist with mechanical ventilation in sedated patients. The blood vessels of the tracheal mucosa can be compressed by high tracheal tube cuff pressures (> 30 cm H2O), leading to reduced mucosal blood flow with resulting ischemia and morbidity. Previous research showed a direct correlation between aircraft pressure altitude and the pressure reading from the tracheal cuff, with resulting pressures > 80 cm H2O at 10,000 ft. Standard practice is to periodically remove air from the cuff during ascent based on assumed increased pressure on the adjacent tracheal mucosa. Using a vacuum chamber and a direct reading micropressure sensor in a 22-mm-diameter semirigid tube, we assessed the direct force applied by the tracheal cuff against the laryngeal tube analog. Standard tracheal cuffs showed direct force/pressure relationships when properly inflated to 20 cm H2O but much less than reported in the literature. Current literature reports values of 55 to 150 cm H2O at 5,000 ft, whereas we report 23 to 25 cm H2O. Our data indicate that a properly inflated cuff does not exceed the critical pressure of 30 cm H2O until the altitude exceeds 8,000 ft. Thus, the standard practice of deflating the laryngeal cuff on ascent should be reconsidered because it may be counterproductive to patient safety.