| Abstract: | Thirty-seven healthy male test subjects, aged 19-21, with different +Gz acceleration tolerance were examined. Their blood pressure (BP) and heart rate (HR) during 5-min tilt tests and 2% water loading tests were measured 2-3 weeks prior to centrifugation. Quantitative evaluation of orthostatic tolerance using an orthostatic index and BP and HR responses to tilt tests before and after water loading revealed specific features of cardiovascular regulation in the subjects with high and low +Gz acceleration tolerance. The negative predictive indicators include: decreased BP, HR and cardiac index in the supine position in combination with high orthostatic tolerance, as well as decreased orthostatic tolerance in combination with a lower function of vasoconstrictor mechanisms in the upright position and a lower sensitivity of carotid sinus reflexes to blood volume changes during tilt and water loading tests. When examining test subjects with high +Gz tolerance, preference should be given to those who can well tolerate tilt tests and show moderately high BP and HR in the supine position, as well as to those who exhibit a noticeable increment of diastolic BP during 5-min tilt tests. |
