Scuba Divers Pulmonary Oedema

Scuba Divers Pulmonary Oedema (SDPE) is a complex, poorly understood, illness, but one that must be recognised by all divers and medicos.

It is called “Drowning from Inside” by some divers and is due to the lungs partly filling with fluid from the pulmonary (lungs) circulation. The cause is not understood and when it results in death, the autopsy is virtually identical to drowning. Many SDPE deaths could be misdiagnosed as drowning and so its real incidence is unknown. One percent of divers in one survey claim to have experienced it.

SDPE causes the diver to feel more exhausted, have some difficulty in breathing, develop tightness, wheezing, crackling or bubbling sounds in the chest. Finally the diver may cough up frothy sputum, sometimes tinged with blood. This happens within minutes.

Once removed from the water, improvement usually occurs over the next few hours, although sometimes the diver appears a little bluish (cyanosis) - especially in the lips. The ideal first aid treatment is 100% oxygen breathing until the hospital takes over. In hospital, the victim is often attached to a ventilator and Positive End Expiratory Pressure (PEEP) may be added. This keeps the airways open at the end of expiration and helps to improve oxygenation.

Almost every claim made about this disorder is debatable, but the current beliefs are that it is a disorder especially prevalent in older divers (40 years or older), more often in women, usually from conservative dives (shallow and nowhere near decompression limits), and frequently worsening during ascent. It often recurs in future immersions (snorkel swimming, scuba dive etc) and usually these divers are advised to refrain from further diving, as death has occurred in subsequent exposures.

The causes are unknown, but a variety of physiological contributions are incriminated.

1. Negative pressure during inspiration (“resistance to breathing”) which could occur from:
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   • Immersion, especially with a head-up/vertical or head-out position
     
   • Inspiratory breathing resistance from diving equipment (regulator, snorkel
     
   • Salt water aspiration, damaging the small pulmonary vessels.
     
   • Reduced gas supply/pressure (low on air).
     
   • Increased gas density with depth
     
   • Increased ventilation, as occurs with exertion, anxiety and hyperventilation
     
   • Inhaling against a tight wetsuit top
     
2. Salt water aspiration, damaging the small pulmonary vessels.
   
3. High blood pressure.
   
4. Cold exposure, inducing hypertension.
   
5. Pre-existing cardio-respiratory disease (possibly not known to the diver).
   
6. Some medications. Beta blockers have been incriminated.
   
7. Other unknown predispositions, or a mixture of the above.
   

Predisposition

An individual predisposition for pulmonary oedema is likely since a diver, snorkeller or swimmer with pulmonary oedema may have other episodes of SDPE, previously or subsequently (in at least 30% of cases). Whether the recurrences relate to the individual diver’s medical status, genetic makeup, dive profile, environmental conditions or the dive equipment, is conjectural. We do not know why most cases occur or recur, but they do.

Differential Diagnosis

Other diseases that can produce pulmonary oedema and cause diagnostic confusion are the salt water aspiration syndrome, drowning, respiratory oxygen toxicity, gas contaminations, cold urticaria, the Irukandji syndrome (jellyfish envenomation) and diving induced asthma. Pulmonary decompression sickness, pulmonary barotrauma and the so-called ‘deep diving dyspnoea’ are diving disorders that may cause diagnostic confusion with SDPE. Anxiety produced hyperventilation may also cause some diagnostic confusion, but this has none of the other respiratory manifestations.‍

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