Patients who are intubated (breathing tube in windpipe) are often transported by air ambulance. Changes in atmospheric pressure during flight may cause pressure increases in the air-filled cuff holding the tube in the windpipe. Studies show that more than half the patients had potentially harmful pressures in the cuff during flight. High pressures lead to complications, such as injury to the windpipe. To avoid injury, cuff pressures must be kept at a safe level. There are many ways to avoid unsafe cuff pressures. One is to inflate the cuff with sterile fluid instead of air. Fluids are not subject to changes in atmospheric pressure. Using fluid, instead of air, in the cuff causes less pressure increases and less windpipe injury. The use and safety profile of this during transport by air ambulance has not been studied. This study compares tracheal tube cuff pressures, filled with air or fluid, at routine flying altitudes during patient transports by air ambulance.