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FITNESS TO DIVE - a patient's guide
Dr Stephen Adams - Visiting Doctor to the Royal NZ Navy
What level of fitness is required for diving?
This a relative term. There is no level of fitness that
guarantees the safety of a diver but there are many illnesses
and injuries that greatly increase the danger.
It is the purpose of a diving fitness assessment to quantify
the risk for the diver, his diving team, instructor, training
organisation, employer or regulatory body. There is no single
standard across all the organisations concerned with fitness
to dive, and in recreational diving there is some discretion
available where the candidate with a full understanding
of the potential risks may be allowed to dive with a waiver.
Occupational diving is generally closely regulated and this
discretion is not available.
The risk to the diver may occur when:
The diving environment exacerbates a pre-existing disease.
A pre-existing disease increases the risk or severity
of a diving accident or illness.
A pre-existing disease complicates rescue, diagnosis or
treatment of a diving illness or accident (or visa versa).
The following is a review and explanation of the major
known and theoretical risk factors for Recreational Scuba
Diving. It is not exhaustive or intended to be a checklist
of exclusions.
Any candidate with these or similar conditions would be
well advised to seek out a doctor with training in diving
medicine.
Age
Young divers may be at risk of dysbaric osteonecrosis
(bone bends) at growth plates but statistical evidence for
this being a problem is lacking. The major observed problems
are strength and size to match equipment and intellectual/psychological
maturity to understand diving principles and apply them
in anxiety producing situations. Fourteen is generally regarded
the minimum age but some younger children can and do dive
safely.
There is no maximum age for diving but older divers may
need increased surveillance for deterioration in general
fitness and specific functions, especially cardiovascular
fitness.
Pregnancy
Scuba diving in pregnancy is generally ruled out as the
fetus is of theoretically greater risk of decompression
sickness (the bends) even when the mother is not affected.
This may lead to birth defects although studies have failed
to show this. Where the mother becomes bent, the risk of
birth defect is high and may be grounds for termination.
General Fitness/Strength
Divers must have enough muscular strength to carry the
wet weight of their equipment (as much as 40 kg) out of
the water - climbing vertically on a ladder against wave
action if necessary. In terms of aerobic fitness it should
be remembered that it may sometimes be necessary to swim
for one's life.
Psychiatric/Psychological
People with significant psychosis, bipolar disorder, or
active depression should not dive. In the first two, lapses
of judgement may carry a high risk of injury while the scope
for self harm if depressed is great. Psychotropic medication
may carry additional risk if side effects occur, and specialist
evaluation of this and risk of recurrence is probably necessary
in those on medication.
Alcohol use increases the risk of diving by its depression
of judgement, response and the vomiting hazard while inebriated
but also by dehydration following heavy use. Chronic alcoholics
may have complications e.g. cirrhosis which make for additional
risk. Non-prescription drugs may also acutely depress judgement
and response while withdrawal effects may be dangerous in
themselves.
Chronic drug abusers are likely to be risk takers and
this group, along with impulsive individuals should not
dive for obvious reasons. People at the other end of the
spectrum who have high anxiety levels or are being coerced
into taking up diving should emphatically not dive and a
dive medical should cover motivation - a failed dive medical
will allow an escape route for the reluctant.
Neurological (Brain) Disorders
In general people with significant neurological deficit
(loss of sensation, strength or movement) should not dive
as their performance will be impaired and put them at risk.
The possibility of decreased consciousness e.g. from epilepsy
or convulsions (fits) is an absolute disqualification from
diving even when well controlled. Some past childhood disorders
e.g. simple febrile convulsion are acceptable but almost
all convulsions in the adult years are not and would at
least require specialist evaluation of risk of recurrence.
Head injury with loss of consciousness or amnesia likewise
requires careful evaluation, including medical records from
the time of injury to determine the risk of later convulsion.
Migraine may be triggered by several aspects of diving
- carbon dioxide build-up, stress, tight fitting wetsuit,
and heavy work. Aside from debilitating the diver it may
result in vomiting into the regulator and should be considered
a relative contraindication. In some areas it is an exclusion.
Heart Disease
A number of heart Problems are definite exclusions from
scuba diving:
Angina or recent heart attack
Intracardiac shunts ("hole in the heart") where bubbles
can cross from one side to another
Heart failure of any type
Other diseases would be subject to tests of heart function
and exercise tolerance:
After bypass graft or angioplasty with no angina.
Mild mitral valve prolapse or regurgitation, mild aortic
incompetence.
Controlled atrial fibrillation (see also anticoagulation)
Controlled hypertension except where treated with diuretics
or beta-blockers.
Lung Disease
Diseases that produce lung scarring - TB, lung fibrosis,
and lung surgery increase probability of lung barotrauma
(pressure injury to the lung leading to collapse of the
lung and/or direct escape of air into blood vessels) as
does previous lung barotrauma, and are absolute exclusions.
Spontaneous pneumothorax (lung collapse) should be considered
a definite exclusion from diving. Other types of pneumothorax
should be carefully evaluated for risk of recurrence and
evidence of lung injury.
Asthma
Obstructive airways disease (asthma and emphysema) also
increase the risk of lung barotauma even when not sick.
Restriction to expiration can be measured in almost all
apparently "well" asthmatics and emphysematics and even
those who have just used their "relieving" inhaler.
Asthma may be triggered by several aspects of scuba diving
- exercise, dry cold air and aspiration of water (which
is extremely common and not always detected by the diver).
In an underwater asthma attack the diver is not only in
trouble from the attack but cannot use medication, may be
at danger from drowning, and is at increased risk of lung
barotrauma during ascent.
Evaluation of asthma in divers is concerned with 3 parameters:
Reaction to inhaled seawater - tested by breathing aerosoled
strong saline
Restriction to exhalation - tested by spirometry (not
peak flow)
Exercise tolerance - from history or an exercise test
Some authorities have banned asthmatics from all diving
while others may permit those who are controlled and pass
such tests to dive recreationally. When an asthmatic diver
is allowed to dive it is usually subject to using their
preventative drug consistently for a time (typically two
months) prior to diving, and to have had no attacks during
that time. Even with excellent control, an increased risk
of diving accident is present and the prospective diver
must understand this. For decompression illness the risk
is thought to be doubled, but other forms of drowning is
also more common due to impaired exercise tolerance.
Gastrointestinal
Diseases provoking vomiting such as active peptic ulcer
and gastroesophageal reflux are contraindications to diving
but a treated ulcer is not.
Active inflammatory bowel disease and degrees of bowel
obstruction are exclusions as is a hernia containing intestine
or paraesophageal, and incarcerated sliding hiatus hernias
due to risk of gas trapping and expansion during ascent
which may result in embolism or perforation.
Divers with stomas may need to release gas trapped in
the bag during ascent.
Musculoskeletal
Mobility and strength are the chief determinants of fitness
to dive. Healed amputations and prostheses (artificial joints
and limbs) do not exclude diving. One should not dive with
active infections or a history of dysbaric osteonecrosis
(bone bends), although some authorities will accept this
where it is limited to long bone shafts.
Ears
The ears are the organ most often injured by the diver,
mostly by barotrauma when one is not able to equalize (pop
the ears). The injuries to the middle and inner ears may
include degrees of deafness and balance problems. One should
not dive if unable to equalize or if a major hearing loss
in one or both ears exists, as risking the remaining hearing
would be foolhardy. Some conditions such as obstruction
to the ear canal, middle ear prosthesis, and stapedectomy
predispose to barotrauma, while vertigo may result in vomiting
underwater or inability to orientate - a potentially hazardous
state underwater. A previously ruptured drum that has healed
or been repaired is okay if it can be equalized easily but
a perforation or other fistula to the middle ear excludes
diving.
Visual
Apart from visual enjoyment of the underwater world, divers
have to be able to read their gauges and visually communicate
with their partner. Loss of corrective lenses underwater
would provide the same problems as a loss of mask but subsequent
rescue may be jeopardized in (worse than 6/18) short-sightedness
by inability to find an exit point.
Radial keratotomy may predispose to globe rupture when
subjected to negative pressure in the mask but laser keratotomy
appears to be safe.
Endocrine
Insulin Dependent Diabetes - there is a risk of hypoglycaemia
(low blood sugar) and confusion or loss of consciousness,
especially following unexpected exercise.
Non-Insulin Dependent Diabetes - controlled by diet without
hypoglycaemias is clearly acceptable but the effect on other
organs e.g. heart should be carefully examined. Those on
tablets for diabetes have some risk of hypoglycaemia but
it is much lower than for insulin.
Dental
The function of the teeth when diving is mainly to hold
a mouthpiece but rupture of a tooth on ascent due to a gas
pocket expanding in a cavity should be avoided by good dental
care.
Skin
Many types of dermatitis may be exacerbated by prolonged
contact with water, abrasion from or sensitivity to rubber
and synthetic materials in scuba equipment.
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