Forceful hyperventilation or breath-holding in or immediately before cold-water immersion can increase blackout, drowning, and arrhythmia risk and should not be part of an in-water class protocol.
How strong the finding is
Established respiratory physiology plus peer-reviewed cold-water autonomic-risk evidence.
What complicates this
No evidence gap justifies combining high-risk breath practices with immersion.
Sources (3)





