The occurrence of cardiac output decrease (via stroke volume) is more pronounced in women than in men during prolonged dry static apnoea.

Little is known on gender differences in autonomic cardiovascular regulation of diving response (DR) and the few available studies into these differences were conducted on subjects with limited or no diving experience. We examined gender influence on hemodynamics during dry-static apnoea (SA) in 8 male and 8 female elite divers matched for their breath-hold (BH) ability. Hemodynamics was assessed by means of simultaneous echocardiography and impedance cardiography measurements and arterial pressure and oxygen saturation (SaO₂) were also collected. In the first quarter (AP25%) and half (AP50%) of apnoea duration cardiac output (CO) showed a more rapid and intense decrease in females than males (-43% vs. -17% during AP25% and -40% vs. -19% during AP50% respectively, P<0.05). At the same time, points systemic vascular resistance (SVR) increased more in women than in men (+22% vs. +100% at AP25% and +48% vs. +107% at AP50% respectively, P<0.05). SaO₂ progressively declined in both groups but males showed a more pronounced decrease than females at the end of apnoeas (-13% vs. -5% respectively, P<0.05). In men, the higher the BSA values the longer the apnoeas, whilst in women, the higher the SVR response the longer the apnoea. In elite female divers, the magnitude of CO decrease during dry static apnoea was larger than in males. Both the capacity to store oxygen and to reduce O₂ consumption play a pivotal role in BH performance but their extent seems to be different in genders.

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