Systolic time intervals during combined hand cooling and head-up tilt.
Cardiac effects initiated by hand cooling and head-up tilt, separately and in combination, were studied in human subjects. Systolic and diastolic arterial pressures, heart rate, pre-ejection period (PEP), and left ventricular ejection time (LVET) were measured while subjects were resting supine, supine with hand immersed in 10 degrees C water, tilted 70 degrees head up, and hand immersed during head-up tilt. Hand immersion and head-up tilt individually increased diastolic blood pressure and concomitantly increased the duration of PEP. During the combined maneuver, the increase in diastolic pressure was greater than observed during either separate maneuver; however, the combined maneuver had no comparable summative effect on PEP prolongation. An interaction appears to occur during the combined maneuver which counteracts the Frank/Starling effect on PEP due to decreased venous return during head-up tilt.