The effect of raised hydrostatic pressure on heart rate variability during breath holding in man

Abstract

Changes in cardiac interval (difference between two consecutive R waves of the ECG) during an expiratory breath hold (16 s) were examined in four divers during a saturation dive to 450 msw (metres of seawater). At 450 msw, breath hold caused a progressive shortening of cardiac interval that was significantly different from the changes seen at surface. The cause and significance of this shortening is unknown, but it might serve to maintain normal cardiovascular dynamics under hyperbaric conditions.