During the flight, airliners normally travel at a height of about 10, 000-12, 000 meters. At these altitudes, it is necessary that the zones for passengers are pressurized, in such a way as to recreate a condition as similar as possible to that found on the ground. Therefore, inside the cabin, the cruising altitude pressure is maintained at values equivalent to those of a height of 1, 800-2, 400 meters above sea level. Thus, after take-off, the decrease in air pressure in the cabin causes the expansion of the gases present inside the body cavities ; similarly, before landing, the increase in pressure in the cabin causes it to contract.
The effects of reducing cabin air pressure are generally well tolerated by healthy passengers. When the plane rises in altitude, air escapes from the middle ear and sinus cavities to balance pressure differences. However, if this flow does not take place, the ears and sinus cavities appear to be blocked and pain may appear. Chewing, swallowing or yawning attenuates discomfort. If the problem persists, it is advisable to carry out the Valsalva maneuver, ie a brief forced expiration with the mouth closed, keeping the nose tight. The inability to compensate for the pressure differences resulting from an inflammation of the upper respiratory tract or an allergic rhinitis can determine - in the worst cases - a baropathy (eg medium barotitis and barosinusitis). Due to changes in atmospheric pressure, the expansion of the gases in the abdomen and chest can also create a slight malaise.
