How many people have flown on a long commercial flight and landed at their destination only to find that a toiletry container had opened and spilled its contents all over their luggage? What causes this mysterious spilling of shampoos and lotions you may ask? And what does Dr Antonio Valsalva have to do with it?
Robert Boyle, 17th century chemist and physicist, discovered that pressure and volume are inversely proportional at a constant temperature. This means that as pressure decreases (as it does with increasing altitude), volume increases at a similar rate.
There are several locations in the human body where gas can accumulate and possibly become trapped. These medical conditions, known collectively as 'Trapped Gases' often lead to discomfort, pain, and possibly destruction of surrounding tissues. The most common locations are:
- Middle ear
- Sinuses
- Lungs
- Gastrointestinal tract
- Teeth
Ear Block (Barotitis Media)
Ear block occurs in the presence of a pressure gradient in the middle ear and an ineffective eustachian tube. When the eustachian tube does not function properly due to inflammation and swelling from an acute upper respiratory infection or allergies, pressures do not equilibrate and this relative vacuum will pull fluid from the surrounding tissue into the middle ear. In extreme cases, the eardrum can rupture.
To avoid barotitis media, one needs to force the eustachian tube to open. This can be accomplished by yawning, drinking, or several maneuvers named after their inventors - the Valsalva maneuver, the Toynbee maneuver, the Frenzel maneuver, or the Politzer device.
Sinus Block (Barosinusitis)
Human beings have 4 pairs of air-filled paranasal sinuses. The medical condition most commonly occurs when moving from a relatively hypobaric environment into one of greater pressure, resulting in considerable pain that can be incapacitating.
Tooth Squeeze (Barodontalgia)
Gas can become trapped in teeth during dental procedures such as when placing a filling. In a pilot or SCUBA diver, these small pockets of air can result in incredible pain or even fracture of the tooth with pressure changes.
Gas Expansion in the GI Tract
As gas expands throughout the GI tract, pain receptors sensitive to stretch often will provoke abdominal discomfort. In certain cases this expansion of gas can be so profound that the diaphragm is prevented from fully descending during inhalation. Abdominal pain can be avoided by staying away from foods that produce gas before flight: beans, broccoli, cauliflower, brussels sprouts, cabbage, and carbonated drinks.
REFERENCES
- Davis, Jeffrey R. Fundamentals of Aerospace Medicine. 4th ed. Lippincott Williams & Wilkins. 2008.