Inside the Cabin
Pressure PhysiologyModern passenger flights fly at high altitudes and despite the fact that they are pressurized, it is not possible to maintain sea level pressure during the flight due to the resulting high differential pressure. Most aircraft maintain a pressure equivalent to 6000-8000 feet above sea level. Reduction of pressure causes gases to expand, with about 20% increase from sea level to 8000 feet.
The human body contains fairly large amounts of gas (including mostly air as well as gases formed in the stomach and intestines during digestion). Expansion of stomach or intestinal gas can lead to discomfort, hence it is better to avoid consuming "gas-generating" food such as beans, cabbage, carbonated drinks and beer before your flight.
The air in the middle ear cavity also expands and contracts with changes in atmospheric pressure. If the pressure is not able to be equalized, the eardrum will be distended, causing pain or temporary impairment of hearing. The middle ear pressure is normally equalized by passage of air through the Eustachian tube, which leads to the space behind the nose (nasopharynx). The tube is normally in a collapsed state but can be opened briefly by swallowing or yawning. Air in the middle ear can usually escape without problems but as the aircraft descends and the pressure is increased, the relatively lower pressure in the tube tends to keep it collapsed and result in negative pressure in the middle ear, causing discomfort or pain.
Opening of the tube can be aided by swallowing, yawning, performing the Valsalva manoeuvre (closing the mouth, holding the nostrils pinched closed and blowing to build up pressure in the mouth and nose) or the Toynbee manoeuvre (closing the mouth, holding the nostrils pinched closed and swallowing).
Sinuses are air-filled cavities in the bones of the face and skull, and are connected to the nasopharynx by small openings. If these openings are obstructed by nasal congestion, there may be considerable pain on descent. The Valsalva manoeuvre may help, but it is better not to fly with nasal congestion, head colds, hay fever or sinusitis. However, if it is essential to fly, the use of a decongestant spray before take-off and before the start of the descent may prevent the problem.
Pain on ascent may also result from the expansion of gas under a new filling, or from a dental cavity or abscess. Hence, it is better not to fly for 24 hours after a dental treatment or if you are suffering from active tooth problems.
Aircraft EnvironmentIn general, most modern passenger jets are quiet and comfortable with good levels of ventilation. All our flights are non-smoking, so the level of airborne pollutants is far lower than on most city streets. Fresh air is added to recycled air through very fine filters to remove dust, viruses, fungi and bacteria, and is delivered to the top of the cabin and extracted at floor level to carry any particles downwards away from the breathing zone.
The air within the cabin is of low humidity, but no more so than many parts of the world, particularly desert regions. This does not cause a problem for most passengers, but some do experience slight discomfort from drying of the skin, eyes and nose. Moisturizers, water atomizers and eye drops are usually sufficient to avoid any discomfort. Most passengers who wear contact lenses have no problems inflight, but some do experience discomfort and prefer to wear spectacles instead.
Motion SicknessMotion sickness is caused by a conflict between the body's sense of vision and its sense of equilibrium and may worsen during turbulence. It can be eased by keeping your eyes fixed on a non-moving object.
If you suffer from motion sickness, try to obtain a window seat since being able to focus on the ground, sea or horizon can sometimes help. The middle of the aircraft near the wings is also usually preferable.
Take It EasyMake sure that any medications that you require during the flight are easily available. If you need to use injectable medications during the flight, a sharps box is available. Please contact our cabin staff for assistance.
Keep yourself hydrated by drinking plenty of water or juice during the flight. Avoid drinking too much tea, coffee or alcohol as these are diuretics and can cause dehydration. Try and eat light during the flight.
There has been quite a lot of recent publicity regarding Deep Vein Thrombosis. Further information is available under DVT and Extra Care, including some inflight exercise that you can do to make your journey more comfortable.
Passengers should be aware that the following devices are not allowed to be operated on board any Cathay Pacific or Dragonair flights:
Potential increased risk of respiratory disease transmission on board has been associated with use of nebulisers, humidifiers, vaporizers or other similar devices in-flight.
- Nebulisers (open-circuit type)
- Personal Humidifiers*
Please discuss the details with your physician.
* Except those attached to CPAP machines of closed-circuit design, with exhausted mist collected without venting into the cabin.