Cardiovascular response to cooling of limbs determined by noninvasive methods

Cold, even local exposure to a limited portion of the body, is a stress to man which elevates arterial pressure, thereby intensifying cardiac workload. The sequence of cardiac events following local cooling was noninvasively studied by observation of changes in cardiac interval, left ventricular ejection time, time from A wave of electrocardiogram to the peak of the dD/dt of the carotid pulse wave (which includes pre-ejection period), and amplitude of the pulse wave from a photoelectric cell on the earlobe, along with arterial pressures. Twelve subjects, aged 22--41 years, exposed a hand or foot to cold water for 1 min while seated and while supine (four experiements each). Results indicate that arterial pressure is monotonically elevated throughout the minute of exposure. Cardiac intervals are initially abbreviated, then return towards control. This may include an initial response to the cold, followed by a baroreflex at the heart. Subject posture and limb exposed also affect cardiac responses.