Central and coronary circulation of the normal man during orthostatic and lower body negative pressure tests

The effects of the tilt test (at 60-70 degrees for 20 min) and LBNP test (at -30 and -60 mm Hg for 20 min each) on the basic parameters of central circulation (15 test subjects) and coronary circulation (11 test subjects) were investigated. The study was performed using thermistor-equipped catheters implanted into the pulmonary artery and coronary sinus and Teflon catheters implanted into the brachial artery. In the study, the basic parameters of central circulation (pressure in the right atrium and pulmonary artery, transmural pressure in these compartments, cardiac index, stroke index, etc.) and coronary circulation (blood flow in the coronary sinus, left ventricle oxygen consumption, coronary resistance, etc.) were measured. Correlation between circulation variations and metabolic requirements was assessed (with respect to changes in acid-base equilibrium of blood). The effect of the tilt test and LBNP test on the basic parameters of central and coronary circulation, blood acid-base equilibrium and oxygenation was compared.