The underwater environment causes a diver to be at a tremendous disadvantage
- the difficulty in propulsion through the surrounding water;
- through rapid heat loss to water generally colder than body temperature;
- breathing gas of compressed density;
- the diver uses an altered cardiorespiratory system from a changed environment;
- in order to prevent damage to air-containing spaces in the body, the diver has to accommodate to changes in gas volume and pressure;
- accommodation to the effects of the partial pressure of gases that can cause toxic, narcotic, stimulatory and gas solubility changes to bodily functions.
Divers have to have a reasonable level of physical and physiological fitness
because of the obligatory stresses of the underwater environment. They must
also be free of other limitations compromising safety in the underwater
milieu. For safe diving, the millions of recreational and sport divers
should maintain a reasonable level of fitness, the medical requirements
for sport diving not being stringent.
Exercise is any activity that raises the resting oxygen consumption above
basal levels. Most parts of the body contain a functional reserve which
can be called up during exercise--this applies particularly to the heart.
Limitations imposed by heart disease may be often assessed by measurements
of maximal heart performance. Many experts have emphasized the need to
measure cardiac reserve through exercise stress testing, and this has
become a useful clinical means for checking physical reserve while diving.
Since heart disease is one of the common causes of sudden death underwater,
fitness for sport diving must include assessment for heart disease risk.
*Underwater swimmers with full scuba gear have been tested for the amount
of work involved; divers must be in good physical condition to swim at
1 knot (101 feet/minute, or about a 9 minute mile).
One met = 3.5 ml/kg/minute, and since VO2 Max is 40, a diver swimming
1 knot should be able to reach and sustain 13 mets on the treadmill.*
Physicians planning to evaluate sport divers require a basic knowledge of
the physiology of diving and a fundamental understanding of the diving
environment. It is helpful if the physician is also a diver himself.
Assessment of fitness for diving must consider physical conditioning
as well as limitations imposed by medical conditions.
The medical evaluation should consider absolute, relative, or temporary
disqualifying conditions as well as excessive smoking and substance abuse.
Poor muscle tone, lack of conditioning, obesity and other evidence of
dietary indiscretion should be a stimulus to advise the diver about fitness.
A medical condition that could injure the diver or his buddy diver should
disqualify the diver. The buddy-diver system is the universally recognized
practice of pairing scuba divers for mutual safety and implies that each of
the pair is fully capable of providing effective aid to the other.
Limitations in one of the buddy pair upsets this balance of safety.
Obesity represents a hazard to divers because of the common lack of
adequate physical condition in obese individuals and because inert
gas exchange and its relationship to decompression sickness are modified
unfavorably. Total body fat of less the 22% in males, and less than 28%
in females is desirable.
DIVER FITNESS AND AGE
The majority of elderly people do not exercise adequately. For diving good
physical condition is essential. Although physical capacity is known to
decline with age (Bruce et aI 1974; Raven and Mitchell 1980), it is unclear
whether the loss of physical capacity is related to age or to the inactivity
common in older individuals. Because of the reduced physical activity
experienced by older individuals, there is a deconditioning effect. Most
elderly divers are not capable of sustaining the work load of younger
individuals. The reduction in physical capacity must be accounted for
when accompanying older divers. Studies in older athletes suggest that
the decline in physical capacity with age can be minimized by continued
physical training (Heath 1980). Elderly divers should be healthy, and
possess a level of physical condition that allows them to dive safely.
Chronic diseases known to be of higher incidence in the elderly present
special problems in diving. A significant and important problem in the
elderly is the high incidence of cardiovascular disease. Atherosclerosis
can affect flow to the brain, heart. kidneys, or skeletal muscles. These
disorders may go undetected and high exercise demands induced by swimming
with diving gear may result in inadequate oxygen supply and abnormal
function of a tissue or organ. Of most importance is the presence of
coronary atherosclerosis with coronary artery disease, heart attack or
sudden death may occur in unfit divers with coronary disease. Avoidance
of serious cardiac problems while diving can be achieved through appropriate
screening evaluation (Linaweaver 1977). Exercise testing is a useful means
of screening in elderly individuals prior to instituting a diving program.
Fitness considerations for young divers are directed towards emotional
maturity, ability to learn and understand the requisite physiologic,
physical and environmental data needed for safe diving, and towards
strength requirements necessary for handling diving equipment
(Dembert and Keith 1986).
Sport diving imposes no legal limits on age, but most diver training
organizations require candidates to be 15 years old for full certification.
Training is provided to younger candidates who receive conditional
certification until age 15. Children divers should use dive profiles
which minimize risk for decompression sickness to eliminate concern for
injury to growing tissues. Equipment must be properly fitted to the young
diver. Equipment designed for adults may be unsafe for a child of small
body habitus. Individual variation in development, strength, maturity,
and intelligence is too wide to set a fixed minimum age for diving.
Customarily, 15 years is the usual minimum age for sport diving in the
WOMEN AND DIVING
Many women have learned the sport of diving, and are active divers. Although
there are few limitations to diving in women when compared to men, most
diving physicians recommend against diving while pregnant. Other than
pregnancy, there are no unique concerns regarding fitness of women divers.
Women usually have a lower strength capacity than men and a lower aerobic
capacity. Women have a higher percentage of body fat. Sedentary women
approximate 25% body fat while trained athletic women reach 10-15%.
Trained males however average 7-10% body fat. Increased body fat in women
provides better insulation from heat loss during diving, and increased
In assessing fitness to dive in women, the same considerations applied to
men regarding general health, physical capacity, mental stability, and
training should be used.
EAR PROBLEMS IN DIVING
Ear problems are the most common medical problems in diving. The ears,
including the ear drums must be healthy in order to dive safely. Fitness
evaluation requires a thorough evaluation of the ears. Aural barotrauma
(ear squeeze) occurs in all divers, and can be avoided by careful attention
to ear clearing during descent, and the maintenance of open air passages in
the ears and throat. A perforated ear drum, chronic ear infections, and
unilateral hearing loss should make a candidate unfit to dive.
Avoidance of pulmonary overpressure injury (barotrauma) is a primary concern
of all divers, because of the potential seriousness of the lung conditions
which can result from diving (Linaweaver 1963). Pneumothorax, mediastinal
emphysema, and traumatic arterial gas embolism can occur from lung
overpressure. In arterial gas embolism the overpressure forces air into
the arterial circulation, and usually to the brain where it can obstruct
blood flow. This event leads to permanent brain damage unless treated
rapidly by recompression therapy (Linaweaver 1963). To prevent injury
divers must be free of spontaneous pneumothorax, chronic pulmonary
disease and asthma.
Divers with neck and back problems may develop nerve injuries from heavy
lifting, climbing and other diving related activities. Some individuals
with severe disease of the spine (herniated disc), may be unable to dive
safely due to limitation of motion or severe pain.
Cardiovascular fitness in diver candidates requires the absence of heart
disease, hypertension and disease of the blood vessels. The use of drugs
for CV disorders may also render a diver unfit.
Coronary Artery Disease
Coronary artery disease is the most highly prevalent, life-threatening
disease in the United States. Its seriousness and prevalence demand
special mention in divers. Two million people per year develop this
disease, and over 500,000 people per year die from coronary artery
disease (American Heart Association 1981). The basic abnormality of
coronary disease is partial or complete obstruction of one or more
arteries which supply the heart. In the presence of increased work
demands, the heart becomes oxygen starved.
There are several consequences of inadequate oxygen supply to the heart
during diving. Oxygen deprived heart muscle may develop sudden reduction
in pumping function.. Marked shortness of breath and lung congestion will
occur with exercise. Although coronary heart disease is usually manifested
by chest pain in most afflicted people, the most troublesome person with
coronary disease is the person who has no symptoms but who develops marked
oxygen deprivation detected only by electrocardiogram. Such people are at
greater risk for sudden death since they developed no premonitory symptoms
when oxygen deprivation to the heart occurs.
Heart Surgery and Angioplasty
Patients with successful coronary bypass surgery or balloon angioplasty
have returned to sport diving. Careful evaluation of the diverís condition
after recovery from surgery and successful demonstration of acceptable
exercise capacity will allow some individuals to return to diving.
Detection of heart disease is particularly important in divers beyond the
age of 40. Significant coronary disease may exist without symptoms, only
to become evident during stress induced by exercise or anxiety. Diving is
an environment which can provoke the first symptoms of coronary disease.
In many cases the first symptom is sudden death.
Testing for coronary heart disease can be done by exercise stress testing,
and should be done in diver candidates over the age of 40 or those with
known or suspected coronary heart disease (Bruce and Hornstein 1969).
Two medical conditions which deserve special mention are seizure disorders
and insulin dependent diabetes. Both of these chronic disorders increase
risk for sudden unexpected unconsciousness underwater. Diving is not
recommended due to this increased risk.
1. Bruce, RA, et al, 1974. Separation of effects of cardiovascular disease
and age on ventricular function with maximum exercise. Am. J. Cardiol.
2. Bruce and Hornstein, 1969. Exercise stress testing in evaluation of
patients with ischemic heart disease. Prog. Cardiovasc. Dis. 11:371-391
3. Bruce and McDonough, 1969. Stress testing in screening for cardiovascular
disease. Bull. N.Y. Acad. Med., (2) 45: 1288-1305.
4. Dembert and Keith,1986. Evaluating the potential pediatric scuba diver.
Am. J. Dis. Children 140: 1135-1141
5. Ellestad and Wan, 1975 Predictive implications of stress testing. Circ
6. Folkow 1971. Role of Sympathetic Nervous System in Coronary Heart Disease
and Physical Fitness. Pp. 68-73. Larson and Malmborg, eds.
7. Heath et al. 1980. A physiologic comparison of young and older endurance
athletes. J. Appl. Physiol. 51:634-640.
8. Linaweaver 1977. Physical examination requirements for commercial divers.
J. Occup. Med. 19:817-818.
9. Linaweaver 1963. Injuries to the chest caused by pressure changes,
compression and decompression. Am. J. Surg. 105:514-521.
10. Master 1950. The two step electrocardiogram: a test for coronary
insufficiency. Ann. Int. Med. 32: 842-863.
I was going to
write a small bio for Dr. Campbell, but there is no way to fit his experience in this
small area. You should visit his personal web site at
http://www.gulftel.com/~scubadoc, at his personal site you
will find information about all major diving medical topics. (Great Site)