oa Endotracheal tube cuff pressure during aeromedical transport

The use of helicopters and planes for transporting sick or injured patients to tertiary care centers is common practice. Aviation medicine requires a different perspective regarding patient care. One must consider the effects of higher altitudes on patients when utilizing aeromedical transportation. An endotracheal tube (ETT) utilizes air to inflate a balloon (“cuff”); the cuff invasively secures the ETT and the pressure must be measured and monitored. The amount of air placed in an ETT cuff to ensure a proper seal on an intubated patient varies among practitioners; without using a measuring device (manometer), ETT cuff pressures are unknown. In a critically ill patient, blood supply to the tracheal mucosa can become compromised, when ETT cuff pressures are sustained above 30 mm Hg for greater than 15-30 minutes potentially resulting in unnecessary airway trauma. Boyle-Mariotte’s Gas Law is used to measure ETT cuff pressures: Pcuff2=Pcuff1 + Patm1 – Patm2. Pcuff2 represents the final numerical value of the ETT cuff pressure. Pcuff1 is the initial pressure of the ETT cuff pressure at ground level, Patm1 is atmospheric pressure at ground level, and Patm2 is the barometric pressure at the cruising altitude of the aircraft. Based on Boyle-Mariotte’s formula, inflating an ETT cuff with a pressure of 18 mm Hg at zero feet ground level, (760 mm Hg) and then ascending to a flight altitude of 500 feet above ground level (746 mm Hg) would increase cuff pressure by 14 mm Hg. Based on an 18 mm Hg ETT cuff pressure at ground level, and ascending to an altitude of 1000 feet, the ETT cuff pressure would increase to 45 mm Hg of pressure-a critically high cuff pressure for a patient that may be hemodynamically compromised. Manometers must be utilized by aeromedical crews for the prevention of ETT cuff-induced tracheal mucosal lesions. References Bassi, M., Zuercher, M., Eme, J.J., &Ummenhofer, W. (2010). Endotracheal tube intracuff pressure during helicopter transport. Annals of Emergency Medicine. 56(2), 89-93. doi: 10.1016/j.annemergmed.2010.01.025 Mann, C., Parkinson, N., & Bleetman, A. (2007) Endotracheal tube and laryngeal mask airway cuff volume changes with altitude: a rule of thumb for aeromedical transport. Emergency Medical Journal 24, 165-167. doi: 10.1136/emj.2006.039933. Raynham, O.W., Lubbe, D.E., & Fagan, J.J. (2009). Tracheal stenosis: Preventable mortbidity on the increase in our intensive care units. South African Medical Journal 99(9), 645-646. Stein, C., Berkowitz, G., & Kramer, E. (2011). Assessment of safe endotracheal tube cuff pressures in emergency care-time for a change? South African Medical Journal 101(3), 172-173.