Effect of different degrees of tilt on cardiac output, heart rate, and blood pressure in normal man.

Many workers have shown that the cardiac output in normal man is less in the upright than in the recumbent position (McMichael and SharpeySchafer, 1944; Stead et al., 1945; Coe, Best, and Lawson, 1950; Wang, Marshall, and Shepherd, 1960; Chapman, Fisher, and Sproule, 1960; Reeves et al., 1961). The physiological events underlying this change are complex and depend on many variables, such as the angle of tilt and length of time the patient remains at a given angle and whether the change is from recumbency to an upright position or vice versa. Posture and its relation to cardiac output here becomes increasingly important with the introduction of hypotensive drugs. The purpose of this study was to determine the relation ofthe angle oftilting to the changes in cardiac output, blood pressure, and pulse rate in normal man.