An aviation medicine 'Dear Doctor'. Dr. Dougal Watson.
From the October 1995 issue of the AOPA (Australia) magazine.
This month Flyin' the ointment considers flying problems associated with SCUBA diving and the dreaded flu that seems to be finding so many of us lately.
FLYING & DIVING.
I'm planning a diving holiday with a couple of friends. We were going to fly a Bonanza to North Queensland and join a week long, live aboard, diving tour from there. We thought there were some problems with flying and diving but don't know any details........
I'm a jealous man. I'd love to be planning a diving holiday at the moment.
You're quite correct, there are a few matters of concern with diving and flying. The main worry is Decompression Illness which is commonly known, in diving circles, as 'The Bends'.
When you're breathing air under water (as in most SCUBA diving) your body is absorbing extra Nitrogen gas. This isn't usually a problem until you head to the surface again. If you surface too quickly or don't take adequate decompression stops the Nitrogen won't be able to leave your body rapidly enough and it will form little bubbles. These bubbles can interfere with the function of any part of your body, especially the lungs, nerves, brain, and skin.
You might have only a few tiny bubbles, causing no problems at all, in your body when you reach the surface. If, however, you go flying the bubbles will expand (due to the reduction in pressure with altitude) and could cause the onset of Decompression Illness symptoms. These symptoms might be little more than a vague sensation of feeling tired or 'crook' or they might be itches and rashes on the skin, pain in the joints, breathing difficulties, or numbness, weakness, or incoordination.
While most cases of Decompression Illness are mild and have no long term effects the disease can cause permanent neurological problems, paralysis, and even death.
There is no 100% certain way of avoiding Decompression Illness (except never diving, flying, or going into pressure chambers) but there are ways of reducing your chances of being afflicted by this disorder. The first thing is to dive conservatively and according to the profiles of a well recognized, well tested, set of dive tables (I'd recommend the DCIEM Sports Diving Tables). Don't believe the sales hype attached to dive computers, none of them are as thoroughly tested or as conservative as the DCIEM tables. Once you've finished diving the best way to avoid Decompression Illness is to treat yourself with respect - don't overdo exercise or alcohol and avoid flying.
The difficult question is 'How long should I wait before flying after diving?' Again there are no hard-and-fast, 100% guaranteed, rules. My practice is to avoid flying for at least 24 hours after a non-decompression dive and 48 hours after a decompression dive. The Royal Australian Navy currently recommends diving within the DCIEM Sports Diving Tables and not flying until your 'Repetitive Factor' returns to 1.0 - the DCIEM table is one of the few sports diving tables that considers flying after diving. The bottom line is the longer you wait before flying the less likely you will be to suffer Decompression Illness.
The other diving / flying problems relate to your ears and sinuses. Any damage or injury to your ears and sinuses during your diving can lead to pain and impairment of function during flight. While an ear that is partly blocked might clear during climb-out it may not during descent. The pain that results can be exquisite and quite disabling. Don't fly until any diving related problems have resolved.
THE FLU AND MY EARS.
...... I've been fighting a chronic flu (for seven weeks now) which seems to have ended up in my sinuses. I haven't been flying since this ongoing battle with the flu virus and so I was wondering about my ears.
Like most sensible pilots you've made the wise decision to avoid flying during your flu. Several years ago I tore both of my eardrums while practising aerobatic spins. I didn't know it at the time but a day later I developed the classic symptoms of a cold. There was already enough swelling, even though I didn't know I was brewing a cold, to impair the clearing of my ears.
During a cold or the flu the linings of your throat and ears swell up. This swelling blocks the tiny Eustachian Tube which connects your ears to the back of your throat. With the eustachian tube blocked the ears can't vent changes in gas volume that occur with altitude (pressure) changes. If the ears are unable to vent pressure can build-up and damage to the ear can result.
As mentioned above you may be able to clear your ears during the climb but it will be more difficult, maybe impossible, to vent them during descent. It is wise to avoid flying until you're completely free of symptoms of the flu and can easily 'pop' both ears by pushing your breath out while keeping your mouth and nostrils occluded (called the Valsalva manoeuvre).
Decongestants such as ''Drixene' spray, 'Sudafed' or 'Cold' tablets are of limited use in preventing these problems and are a potential danger because they can lull you into a false sense of confidence.
Problems with colds, the sinuses and ears were covered in more depth in some articles published here a few years ago ( It's only a cold. AOPA Magazine September 1991. p. 67. Gas collections within the body. AOPA Magazine April 1990. p. 28. ). Maybe the editors will consider reprinting these articles in future editions.
