Abnormal cardiovascular responses induced by localized high power microwave exposure

A hypothesis of microwave-induced circulatory under perfusion was tested in ketamine-anesthetized rats. Fifty-eight ventral head and neck exposures in a waveguide consisted of sham-exposure and exposure to continuous-wave (CW) and pulsed 1.25-GHz microwaves for 5 min. Respiration rate and mean arterial pressure were not altered. Changes in heart rate and pulse pressure were observed in rats exposed to higher power (16-Hz pulses and 6.4-W CW) but not to the lower average power microwave (0.5-Hz pulses and 2 W CW). Depression of pulse pressure, an indication of a decrease in stroke volume, and increased (tachycardia) or decreased (bradycardia) heart rate were noted in presence of whole-body hyperthermia. The cardiac output of those animals exposed to higher average power microwaves was considered to be below normal, as hypothesized. Decreased cardiac output and normal mean arterial pressure resulted in an increase in the total peripheral resistance which was contrary to the anticipated thermal response of animals.