Flying and Health — Page 100, Lesson 151

I want to walk you through a new topic: flying and health, specifically the problems that can arise from gas in the body and from toxic substances around aircraft. Let's start with the gastrointestinal tract. The gastro-intestinal tract is, in effect, a tube from the mouth to the anus. Air can be swallowed along with food, and the digestive processes themselves produce gas. Gas collecting in the stomach can easily escape through the mouth — that's a burp. At the other end of the system, gas in the large intestine, mostly caused by the action of bacteria, can readily be vented to the outside. That's known as "passing flatus." The main problem for a pilot is gas in the small intestine. It has no easy exit from the system at either end. As you climb and the surrounding pressure drops, that trapped gas expands. This expansion causes discomfort and sometimes pain severe enough to cause fainting. Very occasionally, the wall of the intestine may tear. That's a serious medical emergency. There is no easy way to relieve these symptoms during flight except by descending. Descending increases the outside pressure, which compresses the gas back down and eases the pain. But the effects can be greatly reduced by what you do before flight. You should avoid foods that are high gas producers: raw apples, cabbage, cauliflower, celery, cucumber, beer, beans, and any highly spiced foods such as curries. You should eat slowly and not rush meals, especially just before flight. Eat smaller portions — that reduces the amount of air you swallow with your food. And do not use chewing gum, because that also makes you swallow more air. Now let's move to the lungs. The lungs contain a large volume of gas, but there is easy communication to the outside air through the airways, so pressure changes are rapidly dealt with. The only potential risk is from a very rapid decompression. But provided the individual breathes out during that rapid decompression, lung damage is extremely rare. The key point: if the pressure drops suddenly, you must exhale to let the expanding gas escape rather than holding your breath. Next, plaster casts. Air can become trapped inside a plaster cast on a limb. That trapped air will expand as you climb, and it can cause acute distress to the wearer. If you are in doubt about a passenger's cast, it should be split prior to take-off, especially if the flight is going to be lengthy. Splitting the cast means cutting a slit in it so that trapped air can escape. Now let's talk about toxic hazards. Aviation involves the use of many substances that are themselves toxic, or have the potential to become toxic in a fire, releasing dangerous fumes which may be inhaled. In some cases, raised temperature and lowered atmospheric pressure are significant factors in producing or aggravating toxic effects. Even mild toxic effects can lower an individual's performance, and that can result in an aircraft accident. Fuels, lubricants, and propellants can release vapours which may cause drowsiness or irritation to the respiratory system, together with skin damage. Hydrocarbon and lead tetra ethyl can affect the nervous system, causing a loss of sensation. If the sense of smell is affected, an individual's awareness of continued exposure may be reduced — you might not notice you're still breathing in a harmful substance. Anti-icing fluid gives off fumes which, if allowed to enter the fuselage, can be harmful. Ethylene glycol, which is often used in anti-icing fluid, can cause kidney damage. Fire extinguishing agents, particularly Halon 1211 or BCF, may cause suffocation, lung irritation, dizziness, confusion, and coma. These are serious effects, so you need to be aware of the risks if a fire extinguisher discharges in a confined space. Agricultural chemicals, although not normally carried by commercial aircraft, can cause health problems. Some insecticides can be as poisonous to people as they are to the pests they target.