DIVE LOG Australasia

ADVANCED KNOWLEDGE SERIES: PNEUMOTHORAX

Diving Medicine

Why Can’t I Dive? Professor Simon Mitchell, University of Auckland A s a diving physician, one of the commonest questions I hear is “why can’t I dive”; commonly put in relation to a medical condition. The answer is often a nuanced evaluation of risk versus benefit. There are very few medical conditions that represent such a significant risk that diving should probably never be contemplated (and I will discuss one of these below). The approach to most conditions involves carefully assessing the potential risk implied by a particular medical condition, how that risk can be minimised, and whether the potential risks outweigh the benefit of diving. These are often quite complex evaluations that require the doctor to have knowledge of both medicine and diving, and they should involve the diving candidate as an informed evaluator of risk versus benefit.

There are hundreds of medical conditions and potential severities of those conditions that a diving candidate might “bring” to a diving medical consultation, and it is impossible to have a set of established rules that cover all situations. Instead, it is common for diving physicians to apply an analytical three question paradigm in evaluating the potential interaction of any medical condition and diving. First, we ask ourselves “will this condition be made worse by diving”? Second, we ask “will this condition make a diving disorder more likely”? Finally, we ask “could this condition impair physical performance or consciousness in the water”? If the answer to any of these questions is yes, then careful consideration of the advisability of diving must be undertaken. Medical conditions are common, and the above approach to analysing their impact in diving often identifies potential risk, but this does not necessarily mean that the candidate cannot dive. Indeed, if the associated risk seems low or can be managed, then it is typically a matter of explaining that risk to the candidate, describing how the risk might be minimised, and allowing the candidate to make an informed risk acceptance decision to dive (or not). There are, however, several medical conditions that represent what one might describe as “absolute contraindications” to diving. That is to say, if you have them, then diving is generally considered too risky to contemplate. There are other medical contraindications of course, but many of them can be treated and the risk they represent in diving

reduced to a point where diving may be feasible. Unfortunately, this is not so true for several absolute contraindications. I am often asked about them, and so I thought it would be useful to briefly address them in these articles. In this issue I will discuss spontaneous pneumothorax and in the subsequent issue I will discuss epilepsy. Spontaneous pneumothorax The lung is an elastic organ that is effectively trying to collapse all the time. What stops this from happening is maintenance of contact between the lung and chest wall with a small layer of fluid lubricating this contact area in the so-called pleural space. It is a bit like two sheets of glass stuck together with a thin film of water in between. They can slide on each other but are very hard to pull apart. A pneumothorax is a collapse of the lung because of air getting into the pleural space thus breaking this contact. It can occur through a variety of causes, including trauma (such as a broken rib puncturing the lung). The most concerning variant from a diving point of view is so-called spontaneous pneumothorax; named “spontaneous” because it occurs with no obvious precipitating event. Patients who suffer a spontaneous pneumothorax are usually found to have small anatomic defects on the surface of the lung that communicate with the airways, and that are prone to rupture with little or no provocation. Once ruptured, gas from the airway can enter the pleural space and the lung can collapse.

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DIVE LOG Australasia #408 - October ‘24

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