During a scuba dive, subjects undergo environmental constraints such as immersion, exposure to cold, and increased ambient pressure. All of these constraints may be responsible for hemodynamic modifications, which have been well studied in healthy volunteers. Immersion in water induces a cephalad shift of peripheral venous blood that augments central blood volume. Atrial natriuretic peptid and diuresis are markedly increased. Ventilation against resistance induces modifications of intrathoracic pressure and consequently modifications of cardiac preload and afterload.During the scuba dive, increased ambient pressure generates an increase in Po2 and nitrogen partial pressure. A decrease in cardiac output (CO) related to the simultaneous decrease of the heart rate (HR) and the stroke volume (SV) is found at high Po2. Beginning from the partial pressure of 1 atmosphere absolute, an increase in systemic vascular resistance is also observed. add comment
Henry’s law states a proportional relationship between the solubility of a gas in a liquid and the partial pressure of that gas above the liquid. Thus, body tissues saturate with nitrogen during the dive. As the diver returns to the surface, the sum of the gas tensions in the tissues may exceed the absolute ambient pressure, and a state of supersaturation is created.
If the decompression is sufficiently rapid and extensive, the exceeding nitrogen may create circulating venous bubbles from preexisting gas nuclei. Intravascular gas bubbles are carried from the venous circulation to the pulmonary vessel, where they are eliminated through the lungs. The formation of bubbles is recognized as the basis for decompression illness, but such bubbles are also commonly detected in venous circulation of asymptomatic divers. Experimental studies” have proved that right cardiac function and pulmonary arterial pressure may be disturbed by pulmonary gas embolism.
If all these parameters are known to influence cardiovascular function, few studies have investigated the modifications of cardiac function, including left ventricular (LV) systolic and diastolic function, after scuba diving. If there are hemodynamic changes, this could have an importance for the recovery after a dive. Furthermore, these findings could be important for intensivists in the management of decompression sickness.
To our knowledge, in only one study have the cardiac function modifications induced by scuba diving been investigated. But in this study, important hemodynamic parameters such as SV and CO have not been recorded. Consequently, the present study was conducted to assess changes in the hemodynamic status of healthy volunteers after an open-sea scuba dive, using Doppler echocardiography.