Reduced cerebral perfusion on sudden immersion in ice water: a possible cause of drowning.
Level 4 - case-series / case-control
Uncontrolled before-and-after laboratory physiological study in a single small cohort
What was done
Thirteen male volunteers were lowered into a 0 degrees C immersion tank for 30 seconds. Investigators measured mean blood flow velocity in the middle cerebral artery, ventilatory parameters, and heart rate before, during, and after immersion.
What was found
Immediately upon ice-water immersion, heart rate rose from 74 +/- 16 to 107 +/- 18 bpm (p < 0.05). Respiratory rate increased from 16 +/- 3 to 38 +/- 14 breaths/min and tidal volume increased from 883 +/- 360 to 2292 +/- 689 ml. End-tidal carbon dioxide tension fell from 38 +/- 4 to 26 +/- 5 mmHg, and middle cerebral artery mean flow velocity decreased by 43 +/- 8%. Two subjects exhibited signs of imminent syncope (drowsiness, blurred vision, loss of responsiveness), corresponding to velocity drops of 62% and 68%.
Why it matters
This study demonstrates that hyperventilation from the cold shock response causes rapid cerebral hypoperfusion, providing a mechanism for disorientation and drowning during sudden cold-water immersion.
Limits
The sample size was very small (13 participants) and restricted entirely to male volunteers. The study used an uncontrolled before-and-after laboratory design with a brief 30-second immersion, and actual drowning or open-water survival conditions could not be directly simulated.
Cited by
- supports Hyperventilation breathing followed by jumping into cold water has resulted in fatal drownings.