Doppler-echocardiography study of cardiac function during a 36 atm (3,650 kPa) human dive

To determine the influence of a saturation dive on cardiac function, Doppler-echocardiographic measurements were compared at sea level and during a 36 atm (3,650 kPa) He-O 2 dive (gas density: 7 g/liter) in four healthy men. Left ventricular systolic function was studied from time-motion measurements. Transmitral flow (E:A ratio) and isovolumetric relaxation time were used to assess left ventricular diastolic function. Cardiac output was derived from systolic pulmonary and aortic valvular flows. Cardiac output decreased 4.4 ± 0.8 vs. 5.9 1.2 liter/min at sea level) whereas stroke volume, left ventricular ejection fraction, atria and ventricular diameters remained unchanged. Thus, the decrease in cardiac output was attributed to bradycardia (56 ± 8 vs. 73 ± 9 beats/min at sea level) which probably resulted from the slight hyperoxia (Pl O2 , 0.4 atm). We found no evidence of left ventricular diastolic dysfunction. nor did we find valvular regurgitation or pulmonary hypertension. We conclude that Doppler-echocardiography can be used safely to investigate cardiac function during human saturation dives. Our results suggest that a 36 atm He-O 2 dive does not modify cardiac or systolic and diastolic function except for a slight decrease in cardiac output correlated to bradycardia.