Medical Assessment Form For Fitness To Dive (Page 6 of 6) in pdf

Medical Assessment

Form No.:

CFT/IUC409

Sport Diving

Issue No.:

4.2

Dated:

01-Sep-2017

Irish Underwater Council

FURTHER READING (This information is based on SPUMS guidelines , these are stricter than

UKDMC guidelines especially in respect to cardio-respiratory matters)

Diving is a sport carried out in a non-respirable environment using breathing apparatus. Sudden

unconsciousness underwater is usually fatal when using SCUBA equipment, as the relaxation of muscle tone

accompanying unconsciousness results in the breathing regulator falling from the victim's mouth. The diver's

next breath will then be water. This makes any, condition which can cause sudden unconsciousness an

absolute bar to diving. Such conditions include epilepsy and diabetes where the patient requires insulin.

A further problem with the water environment is that pressure increases very rapidly with descent, i.e. by one

atmosphere of extra pressure for every 10 m of depth in the sea. The use of breathing apparatus, providing

gas at ambient pressure, prevents problems of pressure-volume imbalance in the lungs during descent.

However, the middle ears and sinuses will develop problems on descent unless the pressure in these spaces

equals the ambient pressure. There is no way of establishing the patency of sinus ostia by clinical

examination. However, patency of the Eustachian tubes, and so the ability to equalise the middle ear

pressures, can be established easily. Observation of the tympanic membrane while the patient holds his or

her nose, shuts the moth and blows, (Valsalva manoeuvre) will reveal ingress of air to the middle ear by

movement of the drum. The Eustachian tube opening in the nasopharynx is normally closed. Swallowing

opens the ostium. Therefore, a combination of Valsalva and swallowing during the manoeuvre will give the

best chance for air to travel up the Eustachian tube. Another way of opening the Eustachian tube is to

protrude the jaw and wriggle it from side to side while performing the Valsalva manoeuvre. Failure to auto-

inflate a middle ear is an absolute bar to diving until the person can auto-inflate.

A further set of pressure related problems also occur during ascent when the ambient pressure is decreasing.

If an air-filled space cannot vent when the surrounding pressure is reduced, two things can happen. A space

with elastic sides can expand but if the space has rigid walls, the pressure in the space remaining at the

original pressure becomes higher than ambient pressure. The chest wall is elastic, but after a certain

expansion the stretching of' the lungs results in tearing of the lung substance. Air can then enter the

pulmonary venous drainage, pass through the left portion of the heart and be carried to the brain as air

embolism. Unconsciousness and death can result. Thus, any condition preventing normal emptying of' the

lungs is an absolute bar to diving.

Lung cysts, bullae, and other areas that empty slowly or not at all are an absolute bar to breathing air under

pressure. These conditions are best detected by taking an X-ray of the chest in full inspiration and another in

full expiration. Asthma is another such condition. To detect expiratory airway obstruction, a Vitalograph (or

similar) test is required. Experience in the navies of the world, with submarine escape training of' many

thousands, has shown that a disproportionate number of, those suffering burst lungs have FEV1/FVC ratios of

below 75%. Such people do not need to hold their breath on ascent to damage their lungs; all they have to do

is rise too rapidly. People with FEV1/FVC ratio below 75% cannot be considered fit for diving according to

SPUMS guidelines, however the UKDMC/BTS accept a lower FEV1/FVC ratio of 70% as being permissible

to dive as long as everything is clinically normal. A normal FEV1/FVC ratio but clinical signs of bronchospasm,

especially on forced, deep, rapid ventilation is an indication of unfitness to dive. Treatment with drugs for the

aforementioned asthma types is not suitable as the effects can wear off underwater and the combined effects

of pressure and bronchodilator drugs are uncertain.

It is hoped that the foregoing makes the following list of absolute and relative contraindications to diving

logical and comprehensible

Page 6 of 6

Medical Assessment Form For Fitness To Dive Page 6

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