A swimmer who hyperventilates prior to swimming a distance submerged may suffer a blackout and drown.
Rationale: The swimmer hyperventilates to reduce PaCO2, which may prolong the time the person can swim under water before surfacing for a breath.
Downside: The low PaCO2 results in a reduced stimulus to breathe. Strong muscular exertion can consume all of the oxygen, causing cerebral hypoxia.
Clinical features:
(1) The swimmer intentionally hyperventilates prior to making a dive.
(2) The person makes a maximal exertion while submerged.
(3) If the patient remains submerged for a long period, then the person may develop hypoxemia and blackout.
(4) The person may drown if not rescued immediately.
Differential diagnosis:
(1) unconsciousness secondary to trauma during the drive
(2) acute myocardial infarction or other acute injury
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Specialty: Emergency Medicine, Critical Care, Pulmonology
ICD-10: ,
