[Coronary circulation in healthy men during postural changes and decompression of the lower half of the body]

The effect of postural changes (ortho- and antiorthostatic tests) and LBNP on coronary circulation was investigated in 11 healthy male test subjects. Volume blood flow velocity and pressure were measured and blood flowing from the heart was withdrawn using a Ganz catheter implanted into the coronary sinus. A thin Teflon catheter was implanted into the brachial artery. When the test subjects were transferred from the recumbent to the head-up position, their left ventricular oxygen consumption decreased by 3.2 ml/min (21%) and coronary blood flow by 23.8 ml/min (19%), while coronary vascular resistance increased by 32%. When the test subjects were transferred from the head-up to the head-down position (at -15 degrees), coronary oxygen consumption and blood flow increased by 5.5 (46%) and 45.3 (44%) ml/min, respectively, and coronary resistance decreased by 36%. In this situation the LBNP test (-30 mm Hg for 20 min) caused a reduction in oxygen consumption and coronary blood flow by 4.4 (25%) and 37.3 (25% 7 ml/min, respectively, and an increase in coronary resistance by 58%.