Study type: Medical/biological study (experimental study)

Cardiorespiratory changes during microwave-induced lethal heat stress and beta-adrenergic blockade. med./bio.

Published in: J Appl Physiol 1994; 77 (1): 434-440

Aim of study (acc. to author)

1) To characterize heart rate, arterial blood pressure, respiratory rate, and localized body temperature changes that occur during lethal exposure of rats to 2450 MHz microwaves and 2) to investigate the effects of propranolol, nadolol, and labetalol on these responses as well as on survival times and lethal temperatures.

Endpoint

Exposure

Exposure Parameters
Exposure 1: 2,450 MHz
Modulation type: CW
Exposure duration: continuous for 27 to 40 min

Exposure 1

Main characteristics
Frequency 2,450 MHz
Type
Charakteristic
Exposure duration continuous for 27 to 40 min
Modulation
Modulation type CW
Exposure setup
Exposure source
Distance between exposed object and exposure source 115 cm
Chamber The Eccosorb MW-shielded anechoic exposure chamber was maintained at 27 ± 0.5°C and 20 ± 5% humidity.
Setup The animal was placed on a holder consisting of seven Plexiglas rods (0.5 cm O.D.) mounted in a semicircular pattern on 4 x 6 cm Plexiglas plates (0.5 cm thick) and was positioned on the boresight of the antenna with its long axis parallel to the magnetic field (left lateral exposure in H orientation).
Additional info The initial MW exposure was temporarily halted when the colonic temperature of 39.5°C was reached in order to administer (i.p.) the antagonist or saline. When the colonic temperature had dropped to 38.5°C, the final exposure was started and continued until a lethal temperature slightly above 43°C was attained which took between 27 and 40 min depending on the agent.
Parameters
Measurand Value Type Method Mass Remarks
power density 60 mW/cm² mean measured - -
SAR 14 W/kg average over mass measured whole body -

Reference articles

Exposed system:

Methods Endpoint/measurement parameters/methodology

Investigated system:
Investigated organ system:
Time of investigation:
  • during exposure

Main outcome of study (acc. to author)

Heart rate and mean arterial blood pressure did not differ greatly among the groups and were similar to those that occur during environmental heat stress. Lethal temperatures in labetalol- and propranolol-treated rats were significantly lower than in saline controls. Survival time was significantly less in the high-dose propranolol group. Respiratory rate was notably higher in animals treated with propranolol (10 mg/kg). This difference in respiration may have been associated with the significantly shorter survival time in these animals and suggests a vital role of respiration in susceptibilty to microwave-induced heating.

Study character:

Study funded by