Inside the Cabin

      

Pressure Physiology

Modern passenger flights fly at high altitudes and despite the fact that they are pressurised; it is not possible to maintain sea level pressure during the flight. Most aircraft maintain a pressure equivalent to 6000-8000 feet above sea level. Reduction of pressure causes gases to expand, with about 20% increase in volume 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 Environment

In 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.

Cosmic Radiation

Cosmic radiation is a naturally occurring form of ionising radiation that arises from the sun and the galaxies outside the solar system.
The earth’s atmosphere and magnetic field substantially shields the earth from cosmic radiation. People travelling in an aircraft may be exposed to more ionising radiation, because the earth’s atmosphere provides less protection from cosmic radiation at the typical cruising altitudes of commercial aircraft. Exposure also increases the further the flight path is away from the equator. Therefore, the radiation dose will vary between different flights depending on origin, destination, route, flight level pattern and solar activity at the time.
All people are exposed to background radiation at sea level which can come from the local environment, food and drink, medical exposure or building materials. In high doses, radiation can be harmful. However, the doses received at flight altitudes are considered very low. Aircrew and frequent flyers get the most additional exposure because of the extra time they spend at cruising altitudes. 

What are the health effects of cosmic radiation?
Cancer is the principal health effect that has been associated with low-dose ionising radiation.  As all air travel is associated with increased exposure to ionising radiation, it therefore follows that there must be some increased risk of developing cancer. The increased risk is however, extremely small, given that naturally occurring cancer accounts for 23% of deaths anyway in many developed countries.  For example, a person who flies direct return flights from Hong Kong to New York every two weeks for 20 years has their risk of death from cancer increased from 23% to between 23.11% and 23.14%. This represents an increase in percentage over the normal of around 0.5%, which most people would probably not consider unacceptable.
Questions have also been raised on the effects of cosmic radiation on pregnancy and the health of the fetus. Based, on current knowledge, the limited radiation dose obtained during occasional air travel during pregnancy confers very small risks to the fetus.

How much cosmic radiation is there on a flight?
Radiation dose is measured in milliSieverts (mSv). Most Cathay Pacific Airways flights originate or terminate at low latitudes, so we are more fortunate in this respect than airlines based at higher latitude.  An estimate of the radiation dose for a specific flight can be obtained from the following and other websites:
http://www.faa.gov/data_research/research/med_humanfacs/aeromedical/radiobiology/cari6/download/
Some values for flights calculated by computer programs are:

Hong Kong - New York	High Solar Activity Year	0.0688 mSv
New York - Hong Kong	High Solar Activity Year	0.0619 mSv
Hong Kong - New York	Low Solar Activity Year	0.0938 mSv
New York - Hong Kong	Low Solar Activity Year	0.0817 mSv
Hong Kong - Vancouver	High Solar Activity Year	0.0414 mSv
Vancouver - Hong Kong	High Solar Activity Year	0.0465 mSv
Hong Kong - Vancouver	Low Solar Activity Year	0.0501 mSv
Vancouver - Hong Kong	Low Solar Activity Year	0.0551 mSv
Hong Kong - Bangkok	High Solar Activity Year	0.0046 mSv
Bangkok - Hong Kong	High Solar Activity Year	0.0041 mSv
Hong Kong - Bangkok	Low Solar Activity Year	0.0047 mSv
Bangkok - Hong Kong	Low Solar Activity Year	0.0043 mSv

Are there any guidelines on radiation dose limits?
Guidelines concerning radiation exposure have been established by international agencies involved in radiation protection.  In general they recommend the following limits for flying:

• For occupational exposure on commercial air flights (for example pilots and cabin crew) 20mSv per year
• For the general public on commercial air flights 1mSv per year. This includes flying when pregnant.

For additional information please see:
WHO Information Sheet: Cosmic Radiation and Air Travel http://www.who.int/ionizing_radiation/env/cosmic/WHO_Info_Sheet_Cosmic_Radiation.pdf

Disclaimer
The above content provided by Cathay Pacific is for information purposes only. They shall not be used, copied or republished by any persons except expressly authorized by Cathay Pacific. Cathay Pacific has carefully reviewed the contents and taken all steps we consider reasonable to ascertain their accuracy. We do not claim the contents to be comprehensive on the subject matter and they shall not be relied on by any persons who may have an interest in the subject matter. Neither shall they be treated or substituted for medical advice by any persons in relation to the subject matters. We strongly advise and encourage any interested party to the subject matter to seek qualified professional (medical or otherwise) advice for any concerns that he or she may have in the subject matter of the contents.

Communicable Disease

As Hong Kong's airline, Cathay Pacific always puts the health and safety of its passengers and employees as a top priority. We therefore have a number of procedures in place to ensure our preparedness in the event of any serious outbreak of a communicable disease.

Protecting passengers
Cathay Pacific requires medical clearance of all passengers suffering from a communicable disease that pose a direct threat. Where a passenger’s condition poses a significant risk to the health and safety of other passengers or crew they may not be accepted for air travel unless or until the risk has been eliminated.
Procedures are also in place to assist cabin crew if they need to deal with passengers onboard who are suspected to have any kind of infection. The guidelines are in line with those established by the World Health Organization and US Centers for Disease Control and Protection specifically for airline staff and passengers.

Cabin hygiene
With the health of passengers and employees in mind, Cathay Pacific always maintains the highest standard of cleaning and disinfecting for its aircraft cabins, seats, galleys and restrooms. Cleaning procedures are aligned with guidelines issued by various international regulatory and health authorities.

Clean air
Cathay Pacific adopts HEPA (High Efficiency Particulate Arresters) filtration systems that are capable of filtering 99.999% of dust particles and airborne contaminates, ensuring the highest possible quality of cabin air.

Other measures

• We continue to review and reinforce all health procedures in accordance with guidelines issued by regulatory, industry and health authorities.
• We promote public health awareness among our staff. Measures include an influenza vaccination campaign, lectures from prominent experts, and an Intranet website put together by our Corporate Medical Department to provide staff with regular updates on communicable diseases along with health tips.

Medical Equipment Onboard

In case of medical emergencies arising inflight, we have an arrangement with MedAire, Inc. of Phoenix, Arizona to provide MedLink telemedicine service to the aircraft crew. MedLink can provide advice from doctors covering all major specialties round the clock. If a diversion of the plane is required to enable a passenger to receive immediate specialist attention, MedLink has a database of more than 5000 airports and emergency medical resources worldwide, and will arrange for admission of the passenger and appropriate follow-up.

Our aircraft are equipped with comprehensive medical kits and defibrillators for use by the cabin crew. A small amount of oxygen is also carried on board for emergency use by passengers with breathing difficulties, but if you have known respiratory problems, please notify our reservations office in advance, as extra oxygen may be required. For safety reasons, passengers cannot bring their own oxygen cylinders on board.

Motion Sickness

Motion 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. Air sickness bags are available on board. Many over the counter preparations are available and we recommend passengers consult their doctor or pharmacist about the appropriate medications to use.

Eating and Drinking

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.

Inflight Exercise

Prolonged sitting in a fixed position can make you feel uncomfortable in the plane. Following are some easy exercise* that you may wish to follow every couple of hours to loosen your muscles.


1. Start the exercise by sitting comfortably in your seat in an upright position.



2. Rest both feet on the floor. Flex both feet with toes pointing upward, and then point your toes downward.



3. Bend your upper body slightly forward and clasp your hands around one knee. Raise you knee gently towards the chest for a few seconds and then release, placing your feet back on the floor. Continue with the other leg. Repeat 5 times for each leg.



4. Place your hands under one thigh, and gently lift toward your chest. Rotate your ankle in a circular motion for 5 seconds. Repeat with the other leg. Perform this exercise 5 times with both legs.

* We suggest you stop doing these exercise immediately should you feel pain or discomfort.

Illustrations by Bernard Chau. Extract from Discovery, Cathay Pacific's award-winning inflight magazine.