To certify that a person is fit to be taught diving ideally implies that he is physically fit, medically healthy and psychologically stable. Humans are clearly not adapted naturally to dive; if they were they would possess gills. Yet recreational scuba diving is one of the fastest growing leisure sports, and medical standards are required by their patients to be capable of furnishing an opinion as to their medical fitness to dive.
Many physicians limit their consultation to the exclusion of diseases rather than performing a comprehensive assessment based upon knowledge of the different aquatic environments, the myriad of diving equipment and diving gas mixtures available for use and the skills required for the diver's safety.
Why have medical standards? The imposition of medical fitness standards for diving in some part has arisen in response to a perceived risk of serious injury associated with the activity. In many countries, regulations were first developed to protect professional divers and their employers, and this practise of risk management resulted in only the very fit being allowed to enter the profession.
With the advent of a boom in recreational diving, some countries have followed the pathway of mandatory diving medical examinations for recreational divers. This is a prescriptive approach aimed at minimizing the risk accepted by the diving instructor agency, and the candidate has little opportunity to participate in the risk assessment. Other countries have no mandatory requirement for recreational dive medicals; the candidate therefore assumes most of the risk, but is denied the opportunity to discuss this risk with an informed medical practitioner.
Medical standards for recreational diving candidates leave greater room for flexibility than professional diving standards, and are harder to define in absolute terms. The recreational diver has the choice of depth and duration, can avoid adverse environmental conditions, and can usually avoid strenuous exercise (diving medical standards). It is possible to consider voluntary restrictions both on the exposure to different diving environments and their diving practices (depth limits, equipment used, etc.).
Whichever system is in place, there are four important questions to consider when assessing fitness to dive:
1. Does the condition or disease affect the personal in-water safety of the diver?
2. Does the disease or condition affect the safety of the other divers who might have to lend assistance?
3. Will diving exacerbate the condition or disease?
4. Will diving result in any long-term sequelae in the presence of the condition or disease?
Different countries have different approaches to recreational diving medical requirements. In the USA, where the Professional Association of Dive Instructors (PADI) is the largest recreational diving instructional agency, no mandatory medical examination is required. PADI issues to each trainee a scuba diving medical statement that informs the new diver of some of the potential risks involved in scuba diving, along with a medical questionnaire.
If any of the questions are answered in the positive, the candidate must seek the advice of a physician before continuing with the training. If all questions are answered in the negative, then no further medical review is required. A disadvantage with this approach is that the trainees may not be truthful as they are aware a positive answer could disqualify them from diving. There is also no clinical data recorded and no mechanism for reviewing the medical status of the divers as they age, or if they suffer from a new medical condition.
In the UK, the British Sub Aqua Club (BSAC) is the dominant force in recreational diving. Under their rules scuba instruction must not commence until the candidate holds a valid certificate of fitness to dive. The medical is generally valid (unless otherwise endorsed by the medical practitioner) for five years up until the age of 40 years, for three years between the ages of 40 and 50 years; an annual medical is required thereafter. A questionnaire is administered and the examination is in accordance with a specified format.
Australia have produced an Australian Standard AS4005.1 which details the medical criteria to be addressed by individuals who wish to undertake recreational scuba diving. The medical should be conducted by a medical practitioner who has done an approved course of training for medically examining candidates for recreational dive training. The medical examination is only required once before undertaking scuba training, and there is no requirement for follow-up medicals as the diver ages or suffers from a new medical condition. There is, however an option to recommend when such a medical should be performed, on the diving medical certificate.
The physician should clarify, on the medical certificate whether the candidate is medically fit to dive (physician's decision and responsibility) or whether merely advice regarding risk analysis has been given (thus becoming the candidate's responsibility).
In an ideal society, physicians can make recommendations, but not demand obedience from their patients. People do have a right to dive, as long as they do not involve or endanger others. If some candidates decide 'to dive', it is possible that they will ignore the advice and prove the physician incorrect. Diving candidates also have the right to seek alternative opinions from other diving physicians, and sometimes medical colleagues do not share these hard lines. The candidate seeks advice, and if this is given accurately and in detail, he will be more likely to agree with the physician.
A great deal of diving medical practice involves reviewing divers after their local physician has told them that they cannot dive again. Alternately, a great deal of time and effort is required to convince a candidate with a potentially life-threatening disability not to dive if he has been 'passed' by another doctor.
Medical regulations must be explained rationally. Stating that diving should not be allowed while taking drugs epitomizes the opposite attitude. There is no evidence available to suggest that anyone who is taking allopurinol for gout should not dive. The same situation applies to antibiotics for acne, or even chloroquine for malaria prophylaxis.
Medical fitness to dive recreationally should be related to the environmental situation. In some circumstances, no one is fit to dive; in other circumstances, diving is safe for most people. It is often possible to tailor the type of diving to the person being examined.
In many cases, it can be stated that the recreational diver is fit in accordance with specific standards such as those produced by the Australian Standards Association, the National Oceanographic and Atmospheric Administration (NOAA) etc. or the United Kingdom Diving Medical Guidelines. In other cases, it has to be stated that the candidate is fit to dive, but under specific conditions and with specific recommended limitations. These limitations may be due to such conditions as physical disability, obesity, migraine, age, otological problems and visual impairment. Concessions can be more often made for the experienced diver, as compared to the novice.
The following discussion on various aspects of a diving medical evaluation is loosely based on a history and examination form devised by the authors to fill their needs.
Medical Fitness Standards
This subject is still a contentious one. Often we are faced with diving candidates who have demonstrated their physical prowess by excelling in other sports, but who are then informed that they are not medically fit to dive. Thus a champion swimmer, who has active asthma, may well feel that his physical fitness qualifies him for scuba diving. This illustrates a major maxim. Even though a candidate can be very physically fit in one sport, e.g. marathon running, this proves only his fitness for that sport; it does not imply fitness for diving.
Aquatic conditions can change dramatically within a short period of time. The dive may have commenced in good weather, flat seas and no current, yet, it is possible to surface 40 minutes later some 100 metres away from the boat in stormy conditions with a 2-metre swell and over 1 knot of current. The prospective dive candidate must have sufficient reserves to cope with such conditions, and be able to render assistance to his buddy if required. Diving can involve unpredictable and extreme workloads in the unplanned emergency situations produced by currents, tides and changing weather conditions.
Some idea of the candidate's fitness may be assessed by inquiring into his normal daily physical and sporting activities. Those who can swim 200 metres without fins in 5 minutes or less are far more likely to succeed in diving than those who cannot achieve this relatively undemanding standard. It also follows that the dive instructor agency must take some responsibility for ensuring all dive candidates can demonstrate adequate in-water skills before progressing to open-water dives.
Psychological And Psychiatric Considerations
A full psychiatric assessment is impossible to perform in the limited time of a routine diving medical examination, but some clues can be gleaned. A personality characterized by a tendency to introversion, neuroticism and global mood disturbance is more likely to panic (37 per cent of recreational diving deaths are due to this diver error). Useful insight may be gained by direct questions regarding the motivation to dive, a history of claustrophobia, hydrophobia and previous water sports. In order to respond appropriately during a diving emergency, the candidate will need to display emotional maturity and stability.
The diving instructor is in a better position to assess the candidate's psychological suitability for diving during the period of instruction.
Freedom from gross psychiatric disorders is essential. There should be no evidence of: anxiety states, depression, claustrophobia or agoraphobia, psychoses or any organic cerebral syndromes. A history of antidepressant, tranquilizer or other psychotropic drug intake is important both as an indication of psychopathology and because of possible interactions with diving. The candidate with a history of alcohol or other drug abuse should be assessed critically.present. Some2 have suggested that the ability to perform exercise up to 13 metabolic equivalents (METS) be considered a reasonable minimum for engaging in diving activities from a performance- criteria point of view. The means by which this is tested is at the discretion of the physician.
With increasing age, allowance must be made for a more conservative approach to diving activity, as well as to restricting the decompression schedules. This author arbitrarily recommends that older divers reduce their allowable bottom time by 10 per cent for each decade after the age of 30 years.
As a general rule, it is recommended that diving in excess of 9 metres should not be allowed prior to a child reaching osteogenic maturity, i.e. when the epiphyses have fused. This is a very common statement, but there is very little evidence that decompression sickness has really influenced bone growth in young animals. Nevertheless, the possibility makes for hesitation, when recommending that children be allowed to dive in excess of this depth.
Children, although they may be trained in diving techniques, often do not have the physical strength or psychological stability to cope with the occasional unexpected hazards of diving. A child exposed to scuba training must be totally and completely under the control of a competent adult diver, of instructor standard. A salutary warning about allowing children to dive is given by reference to the age range in the fatality statistics. So far the youngest child to die while scuba diving was aged 7, but many were between the ages of 10 and 14 years.
No upper age limit applies provided that the candidate meets all medical standards. Although physiological age is more important than chronological age, for divers over 40 years it is recommended that regular re-examinations be carried out in order to detect medical abnormalities, which may interfere with efficiency and safety in the diving environment. Electrocardiographic (ECG) examinations during maximal exercise may be recommended as part of this medical, especially if cardiac risk factors are
Weight should be less than 20 per cent above the average ideal weight for age, height and build. Obesity is undesirable because it may increase decompression sickness (DCS), even though it may reduce the likelihood of hypothermia. For sport diving, it is permissible to allow diving with obesity that would not be accepted in professional or military diving. This is achieved by imposing an added safety margin in calculating the allowable duration of the dive. With divers who are obese, the bottom time is reduced, depending on the degree of obesity.
One arbitrary standard, used for many years at the Australian Diving Medical Centres, has been to reduce the allowable bottom time for the dive according to the percentage that the candidate's weight exceeds that expected for height and build. Appropriate tables or an index such as the body mass index (weight in kg/height in metres2) (BMI) can be applied. Thus, if the BMI is exceeded by one-third, the permissible no-decompression bottom time for a given depth is reduced by one-third, but the longer duration is used for decompression calculations. An 18-metre dive allowing 60 minutes in the tables would allow an actual bottom time of only 40 minutes in this example.
The candidate's occupation may give some indication of his physical fitness, but may also be important inincreasing the relevance of diving hazards, e.g. aviators or air crew should be advised of the flying restrictions imposed after diving. Sonar operators and musicians may not wish to be exposed to the possible otological complications of diving, which may prejudice their professional life.
A thorough drug history is important in that it may give a clue to the presence and/or severity of otherwise undetected but significant diseases, such as hypertension, cardiac arrhythmia, epilepsy, asthma or psychosis. Also, the effects of drugs may influence diver safety and predispose to diving diseases. Both therapeutic and 'recreational' drugs should be considered.
The existence of serious cardiovascular disease disqualifies the candidate from diving because of the risk of sudden collapse or decreased exercise tolerance. These diseases are responsible for 12-23 per cent of the deaths in recreational scuba diving. Any abnormality should be investigated fully prior to the issue of a fit-to-dive certificate.
The maximal stress exercise ECG is a valuable addition to the medical examination of all divers over the age of 45 years, and those younger where significant coronary risk factors are present. It is important to remember that significant coronary artery disease may be present despite a normal physical examination.