Some effects of breath holding and apneic underwater diving on cardiac rhythm in man.

Abstract

Man's bradycardic response to simple breath holding was augmented by submersion in water of 27 C and was not prevented by muscular exercise. Cardiac arrhythmias occurred with 45 of 64 periods of apnea in 16 subjects and were more frequent during the dives than during breath holding. These arrhythmias, with the exception of atrial, nodal, and ventricular premature contractions, were inhibitory in type and included sinus bradycardia and arrhythmia, sinus arrest followed by either nodal escape or ventricular escape, A-V block, A-V nodal rhythm, and idioventricular rhythm. T waves frequently became tall and peaked during both breath holding and dives. Prompt return to normal sinus rhythm was the rule with the first breath after surfacing. Sinus tachycardia, sinus arrhythmia, and atrial, nodal, or ventricular premature contractions were seen during recovery. Submitted on October 9, 1961