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The actual incidence is unknown, but very likely it is under diagnosed. Both clinically and
pathologically, the appearances are similar to salt water aspiration, near-drowning and
drowning (Chapters 25 and 26).
Extreme exertion may be observed in some cases, but it is often specifically denied.
Predisposition
An individual predisposition for pulmonary oedema is likely since a diver, snorkeler 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, the dive profile, environmental conditions or the dive equipment, is
conjectural. We do not know why most cases occur or recur.
Causes
Many causes have been incriminated. The common factor is a damage to the pulmonary
capillaries, with leakage of fluid from the pulmonary capillaries into the lung alveoli
(“drowning from within”). This may be more likely if more than one “stress” is put on these
capillaries.
The stresses may include;
Pre-existing cardiac disease (possibly not known to the diver)
High blood pressure,
Cold exposure, inducing hypertension,
Salt water aspiration. See Chapter 26.
Intrathoracic blood pooling induced when the body is submerged
.
Negative pressure during inspiration, which could occur from:
•
Immersion per se, especially with a head-up/vertical or head-out position
•
Inspiratory breathing resistance from diving equipment (regulator, snorkel)
•
Reduced gas supply/pressure (low on air)
•
Excessive gas density with depth
•
Increased ventilation, as occurs with anxiety and hyperventilation
•
In rebreathing equipment, when the counter-lung is positioned above the lung
•
Tight chest clothing (wet suits)
Drugs, such as beta-blockers
Treatment
Rescue the patient from the water. Administer oxygen and rest. Positive pressure respiration
may be needed in severe cases. Although improvement is relatively rapid after leaving the
water, cases of unconsciousness have been well recorded, as have deaths. Deaths are likely to
be attributed to drowning, like so many other deaths in the underwater environment.
Medical assessment is required to verify the illness and exclude any predisposing
features. Although SDPE may develop in divers with no medical problem, sometimes
it is based on other diseases, such as cardiac or respiratory diseases. Thus, once it has
happened, investigations to exclude such predisposing factors need to be undertaken.
Thus SDPE, especially in older divers, should be an indication for comprehensive