*3.2.1 Cabin pressure*

At a normal altitude of 36,000–40,000 feet, the cabin pressure equals that of 6000–8000 feet at sea level and is therefore at low levels resulting in a decrease in oxygen supply [20–22]. This is not dangerous for healthy people unless there are cardiopulmonary problems and hematological disorders, for example, sickle cell anemia. These problems are particularly pronounced when the airplane rises (because of the reduction in air pressure in the cabin, outflow from the middle ear and nasal cavities) and also during the cathode of the plane where there is an increase in air pressure in the cabin, inlet air, and the middle ear to balance the pressures. The reduced air humidity in the flight cabin of 10–20% (optimally 40–70%) in conjunction with other factors such as reduced drinking volume, excessive sweating, or increased diuresis due to increased alcohol/coffee consumption can promote the development of dehydration, respiratory diseases, and finally of deep vein thrombosis.

## *3.2.2 Moisture content*

It is low in cabin <20% and can cause skin dryness and eye and nose discomfort. Moisturizing lotion and sunscreen are recommended, whereas contact lenses are contraindicated.
