HIGH-PEAK-POWER MICROWAVE PULSES - EFFECTS ON HEART-RATE AND BLOOD-PRESSURE IN UNANESTHETIZED RATS

Introduction: Exposure sources capable of generating high-peak-power m icrowave pulses, with relatively short pulse widths, have recently bee n developed. Studies of the effect of these sources on the cardiovascu lar systems of animals have not been reported previously. Methods: We exposed 14 unanesthetized male Sprague-Dawley rats to 10 high-peak-pow er microwave pulses generated by a transformer-energized megawatt puls ed output (TEMPO) microwave source, at frequencies ranging from 1.2-1. 8 GHz. Peak power densities were as high as 51.6 kW/cm(2). At 14 d pri or to irradiation, the animals were implanted with chronic aortic cann ulae. With appropriate shielding of the transducer, blood pressure rec ordings were obtained during microwave pulsing. Results:ln a prelimina ry series of exposures at 1.7-1.8 GHz (peak power density 3.3-6.5 kW/c m(2)), an immediate but transient increase in mean arterial blood pres sure (significant) and decrease in heart rate (non-significant) were o bserved. A loud noise was associated with each pulse produced by the T EMPO; this factor was subsequently attenuated. In a second series of e xposures at 1.2-1.4 GHz (peak power density 14.6-51.6 kW/cm(2)), there were no significant changes in mean arterial blood pressure or heart rate during microwave exposure. Conclusions: The earlier significant i ncrease in blood pressure that occurred during microwave exposure appe ared to be related to the sharp noise produced by the TEMPO source. Af ter appropriate sound attenuation, there were no significant effects o f exposure to the microwave pulses.