[Effects of hydrostatic pressure on cardiac function in human]

Effects of hydrostatic pressure on cardiac function were measured by echocardiography and radiography. Seven normal subjects (three females and four males) aged from 21 to 45 years were performed echocardiography on long axis of the heart at standing position in air and in head-out water (36 degrees C) immersion. A same trials were done at long sitting position in four subjects (one female and three males). The measurement of cardiac functions was calculated by Pombo's method. A chest radiography of a normal male individual (45 years) was taken at the time of functional residual capacity of lung in air and in head-out water (36 degrees C) immersion. For taking the chest radiography in water and in air, a box made by wood was used. X-ray exposure was synchronized with R wave of electro-cardiogram. The end-diastolic left ventricular volume, end-systolic volume and cardiac output in water immersion were significantly increased to compare with that of in air. Mean +/- SD of these percent changes were 213 +/- 71% (p less than 0.005), 193 +/- 90% (p less than 0.05), 220 +/- 83% (p less than 0.005), respectively. A same results were obtained at long sitting position. There was no significant changes on the heart rate between in water and in air. The circumstance of the abdomen decreased significantly in water immersion in comparison to in air. The percent change was 94.4 +/- 3.1% (p less than 0.001). There was a significant correlation between percent changes of abdominal circumstance and percent changes of end-systolic left ventricular volume (r = 0.754, p less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)