Cabin air, air pressure and health

The air pressure inside a cabin is usually lower than the air pressure at sea level even after effort and technological advancement to minimise the gap. At in the range 11 000– 12 200 metres (36 000–40 000 feet); i.e. a typical flying level,  the air pressure in the cabin is equivalent to the outside air pressure at 1800–2400 metres (6000–8000 feet) above sea level. As a result, less oxygen is taken up by the blood (hypoxia) and gases within the body expand. The effects of reduced cabin air pressure are usually well tolerated by healthy passengers. Hypoxia can result in passengers with certain medical conditions, particularly heart and lung disease and blood disorders such as anaemia (mainly sickle cell anaemia and iron deficiency anaemia), who may not tolerate this reduced oxygen level (hypoxia) very well.

 

Gas expansion is a normal phenomenon encounter due to decreasing cabin air pressure when the aircraft climb. Reverse happens during descend of air craft (i.e. gases contract). These changes may have effects where gas is trapped in the body (e.g. middle ear and sinuses).Airflow due to change in cabin pressure can sometimes be perceived as a “popping” sensation in the ears. If normal airflow in the middle ear this does not happen, the ears or sinuses may feel as if they are blocked and, if the pressure is not relieved, pain can result. Swallowing, chewing or yawning (“clearing the ears”) will usually relieve any discomfort. If the problem persists, a short forceful expiration against a pinched nose and closed mouth (Valsalva manoeuvre) will usually help. For infants, feeding or giving a pacifier (dummy) to stimulate swallowing may reduce the symptoms. People with ear, nose and sinus infections should avoid flying because pain and injury may result from the inability to equalize pressure differences. Nasal decongestant will be of help where travel cannot be avoided. Passengers who has undergone a abdominal or eye surgery should consult to GP or travel medicine clinic before travelling as some forms of surgery, other medical treatments or diagnostic tests may introduce air or other gas into a body cavity which may result in stomach problems due changing pressure during air travel.

 

Ozone (a form of oxygen with three, rather than two, atoms to the molecule...i.e. O₃) is higher in the upper atmosphere. Higher level of ozone (enter the aircraft cabin together with the fresh air supply) may lead to irritation of the eyes, nose and lungs. However, modern aircrafts are equipped with technology to reduce inside ozone level.

 

As cabin humidity is usually less than 20% (humidity in the home is normally over 30%), it is likely to experience skin dryness and discomfort of the eyes, mouth, nose and exposed skin but causes serious risk to health. One can use a skin moisturizing lotion, saline nasal spray to moisturize the nasal passages, and spectacles rather than contact lenses can relieve or prevent discomfort.