FITNESS TO DIVE - a patient's guide
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
Many types of dermatitis may be exacerbated by prolonged contact with water, abrasion from or sensitivity to rubber and synthetic materials in scuba equipment.