REPORTING POINT 11-99
AEROMEDICAL NEWS
“Live healthy...live well”
HEALTH NEWS
by Larry Kline
SWAPA Voice Mail Box 511/email lwkline@compuserve.com
HOW NOISE AFFECTS HEARING - noise destroys delicate, bristly cells that line the snail-shaped chamber of the inner ear, or cochlea. These so-called hair cells are responsible for translating incoming sound waves into electrical impulses - to be interpreted by the brain.
Just how dangerous a sound is depends on its intensity and duration. An hour’s exposure to blaring tunes may wilt thousands of hair cells for an afternoon, but most will bounce back and so will your hearing. In contrast, a single explosive blast louder than 160 decibels - such as a shotgun blast at close range - can instantly kill the sensitive sound detectors by splitting open the membranes on which they sit.
A more common injury arises from frequent exposure to milder levels of loudness. If regularly battered by sound, individual cells eventually lose their resilience and die. Though initially unnoticeable, the destruction is cumulative. By the time you begin to have difficulty understanding conversations, you may have lost 30 to 50 percent of the 15,000 hair cells in each ear.
Most of this insidious exposure occurs on the job. Sounds that exceed the 80 to 85 decibel limit considered safe are similar to the buzz of a power mower or leaf blower, or the APU exhaust - but it all adds up to hearing damage.
Using a sound meter, movies have been measured at 118 decibels and nightclubs have reached 126 - levels that if sustained at that intensity, could do lasting damage in just minutes.
Obviously, aging contributes to hearing loss - especially hardening of the arteries and other common aspects of “acquired seniority”. But noise damage seems to be the major cause of hearing loss in the 3,000 to 4,000 hertz range - the pitch of consonant sounds in speech.
Researchers are still investigating how noise inflicts damage at the molecular level. One leading theory speculates that overtaxed hair cells emit increasing amounts of unstable particles (free radicals), that then enter the blood vessels to do cellular damage to hearing. If this theory is accurate, antioxidants may repair cellular damage and contribute to reduced hearing loss. Some animal studies have already shown that a squirt of antioxidant medicine deep into the ear seems to reverse some hair-cell damage. (However, there is currently no evidence that antioxidants absorbed through dietary foods or supplementation can help repair hearing damage.) Using this “in your ear” approach to supply antioxidants directly to the ear, researchers at the Naval Medical Center in San Diego have apparently restored the hearing of several people whose hearing perception had been significantly dulled by noise or medication. This treatment also appeared to eliminate tinnitus (ringing in the ears). So far, the number of test subjects has been small, but results are promising. Also, it must be noted the timing is crucial; damage left untreated for more than a few weeks is probably irreversible.
The military has a strong interest in the loss-of -hearing research - since they spend $1.5 billion a year treating hearing-related disabilities.
Since we must live and work in a “silence-challenged” environment, at least give your hearing a rest. Wearing ear plugs when exposed to harsh noises can save your hearing and help prevent long-term hearing loss. Health 7/99.
LATE-NIGHT MEALS STAY WITH YOU LONGER - in a recent study, people on a 2,000 calorie diet gained weight when they got all their calories at dinner - when they ate the same meal earlier in the day, they actually lost a few pounds.
Eating the majority of your caloric intake late at night signals the body to send insulin surging into the bloodstream, which in turn makes it more likely that these calories will be stored as fat by the body.
Don’t skip breakfast, eat a hearty lunch, and dine early to help your body assimilate the food you consume. Health 7/99.
IT'S ONLY A COLD ! By Dr. Dougal Watson (submitted by Captain Paul Christiansen -PHX)
So your throat is sore, your nose running, and your head throbbing as if to burst. You can't help speaking with a characteristic nasal twang causing friends and colleagues alike to comment or ask "Got a cold have we?". Between coughs and sniffles you're forced to reply "Yes, but it's not a problem. It's only a little cold, I should be over it in a couple of days !".
This is a familiar story around most homes and workplaces and indeed a cold usually isn't much of a problem. The situation could be very different if, however, you plan to travel in an aircraft while suffering from this usually inconsequential ailment.
I'd like to tell you a little bit about colds, what they are, what they do to your body, and most importantly how these effects can alter your suitability to pilot an aircraft. This should allow you to make an informed decision, the next time you've got a cold, concerning your fitness to fly.
A cold is proper cause for taking the responsible action of voluntarily and temporarily grounding yourself from flying. I've suffered the pain and distress of bilateral haemotympanum (that's bleeding into the ear drums of both ears, the stage before perforation or rupture of the eardrums) during an aerobatic spin sequence when, unknowingly, I was brewing a cold. I've also seen usually stout military aircrew reduced to tears of pain during descent because having a cold rendered them unable to clear the pressure in their facial sinuses(1). Although a minor ailment to most folk a cold is a potential disaster to aviators (and those that fly with us).
What is a cold ? A cold is an infection, caused by any one of a hundred or so related rhinoviruses (2). It usually takes one or two days for a cold to incubate or brew once you've caught it.
The first symptoms you notice are usually tiredness and irritability along with a tickley, scratchy throat, blocked or runny nose, and a mild headache. The runny nose (rhinorrhoea) usually increases over the next couple of days and then settles rather rapidly as the whole illness resolves. Bouts of sneezing may also occur. A fever is unusual during the common cold. A small number of people (around 1 ‑ 2%) will develop bronchitis at the same time and have a cough that produces quantities of sputum (phlegm).
Most of us use the word cold in reference to any illness or infection of the nose, throat, ears, and lungs that involves a runny nose or mild cough. Many other viruses (3) are also able to cause diseases similar to the common cold. The illness caused by these other viruses is often more severe than a common cold and may involve quite marked cough, fever, sore throat, or even pneumonia.
The common cold, along with any of the above mentioned viral upper respiratory tract infections, is often more severe in children.
You won't be surprised to hear that colds are more common in the winter and autumn. Nobody is certain why this is the case but it may have something to do with the increased time we all spend indoors close to other people during the colder months.
For the purpose of this article I'm not going to distinguish between all of these related but different illnesses. I'm simply going to use the word 'cold' to denote any, or all, of the above ‑ after all they have similar relevance to aviators.
What happens during the infection? The offending virus usually gains access to your body through the lining tissues of your upper airways, especially the nose or throat. It invades the cells there and sets about doing what viruses do best, trying to produce more of its kind and send them forth into the world to infect other cells and produce even more viruses. To do this the virus must hijack machinery and equipment within the cell. This machinery is reserved for the cell's privileged use and the hijacking may set off alarms and alert the body's defense (or immune) system.
As the virus multiplies the cell may rupture and millions of new viruses spill into the bloodstream or nearby tissues. This release of new viruses may also alert the immune system's equivalent of 'customs and immigration', ever watchful for viruses without visas. The release of new viruses causes the cell to die and the immune 'homicide squad' may also be called.
The alerted immune system then mobilizes to seek and destroy all viruses, bits of viruses, and hijacked, infected cells. This is usually achieved rapidly and the illness rarely lasts much longer than a few days. This response almost invariably results in swelling of the infected areas as the battle rages between the immune system and the infecting virus.
Once a virus has been vanquished the immune system 'remembers' it, and is able to recognize its closer relatives, for a time. It is still possible for a not‑so‑closely‑related virus to cause another cold soon afterwards and the memory eventually fades so that the same virus may again cause a cold some time in the future.
You can spread a cold to others because as you breath out virus particles may leave your nasal area in the air or within tiny fluid droplets. If someone near you breaths in some of the virus particles the whole process may start afresh in their nasal passages.
How can a cold affect flying? The two features of a cold that are most important to aviators are the overflow of new viruses into the bloodstream and the swelling of nose and throat tissues.
The first of these, the release of new viruses from their host cell into the body is often called the 'viraemic phase' (4). This viraemic phase usually results in the headaches and general feeling of tiredness, lethargy, and unwellness (5) that is usually associated with a cold.
Anything that makes you feel tired and unwell is a distraction from flying and may well impair your decision making abilities at a critical moment. The viraemic phase of a cold is no exception and our mental and physical performance is always impaired. As aircrew we can ill afford any impairment of our performance that may affect our safety and that of the craft we fly and those that choose to fly with us.
As the tissues lining the nasal area swell the tiny openings to the ears (eustachian tubes) and the sinuses (ostia) become narrowed and may close over. Closure of these small tissue lined tubes makes ear and sinus pressure equalization difficult or impossible. Inability to equalize our ears and sinuses during ascent or descent may result in pain and tissue damage. The term barotrauma (as in barometer) is used to refer to these pressure related tissue damage.
The pain of sinus and ear barotrauma can be of crippling intensity leaving the sufferer unable to devote attention to the task of flying. The tissue damage, which could include rupture of the ear‑drums or the filling of a sinus with blood, may adversely affect our short and long term "fitness to fly". It's really not worth the risk.
What can you do? The first action for an aviator with a cold is the simplest but often the most difficult. When you have a cold you are most certainly not fit to fly. It's as simple as that, the risks are just not worth it. To fly whilst suffering a cold a professional aviator would be exposing his passengers, cargo, and employer to an added, avoidable risk while a sports aviator exposes himself, his passengers, and his craft to the same unnecessary risks.
As an air passenger you are still exposed to the same risks during a cold. It is unlikely, though, that as a passenger you could cause the wreck of an aircraft or the injury of others. Should you choose to travel by air as a passenger while you've got a cold there's a few things you might find useful knowing.
There is no cure (yet) for the common cold! Our immune system is the only avenue we have for ridding our body of the cold virus. To function at its peak our immune system must be maintained by a sensible and well balanced diet. Large doses of vitamins or mineral supplements do not cure the common cold. The body also requires adequate rest for its immune system to remain in peak condition.
Antibiotics do not cure colds! Viruses are immune to antibiotics. It is only when the cold is likely to become complicated with a second, overlapping bacterial infection that antibiotics have any place at all in the management of colds. Anyone healthy enough to maintain an aircrew licence is extremely unlikely to suffer any bacterial complications of a common cold.
It is only if the cold symptoms are sufficiently severe that medication has any place in the treatment of a cold. Even then the only effect that medicine will have is some relief of the symptoms. Medication can't cure or dispel a cold. Aspirin (6) or Paracetamol (7) will help to relieve a headache or sore throat and may settle a mild fever. Decongestants (8) will reduce some of the swelling of the nasal lining tissues and may make it easier to equalize the ears or sinuses. It may also be possible to relieve an irritating cough with a cough mixture or tablets.
Conclusion: a. A cold is an upper respiratory tract infection caused by any of a large number of viruses.
b. There is no cure for a cold, the body's immune system must be allowed to fight the infection.
c. Adequate rest and a sensible diet are the best ways to help your immune system.
d. Flying with a cold is just not worth the risk! (Editor’s note-you also expose fellow crewmembers to your cold and risk making your whole crew ill-LK)
This article was originally published as: “It's Only A Cold!” in the AOPA (Australia) Magazine, Vol. 44, No. 9, September 1991. Comments should be directed to the author, Dr. Dougal Watson ‑ dxw@ozemail.com.au
