To study the effects of the central nervous system stimulant, doxapram, on the thermal responses to 2.8 GHz pulsed radiofrequency radiation in anaesthetized rats.
The 2.8 GHz frequency is characteristic of high power stationary tracking radars for military applications. In view of previously reported hyperthermic effects of doxapram in rodents, it is possible that doxapram may act to reduce the hyperthermic response to radiofrequency radiation and may be of value in cases of accidental exposure at high power densities.
| Exposure | Parameters |
|---|---|
|
Exposure 1:
2.8 GHz
Modulation type:
pulsed
Exposure duration:
intermittent, about 7-10 min on/11-20 min off, for 2 x 3 cycles, see below
|
|
| Frequency | 2.8 GHz |
|---|---|
| Type | |
| Exposure duration | intermittent, about 7-10 min on/11-20 min off, for 2 x 3 cycles, see below |
| Modulation type | pulsed |
|---|---|
| Pulse width | 2 µs |
| Repetition frequency | 500 Hz |
| Exposure source |
|
|---|---|
| Setup | Anaesthetized animals were positioned on a Plexiglas holder and exposed in the H-orientation with their long axis parallel to the H-field. |
| Additional info | Animals were exposed until their colonic temperature rose to 39.5°C. Exposure was repeated when the temperature returned to 38.5°C. This procedure was repeated for three cycles. Then, at 38.5°C, either doxapram or saline was administered i.p. After a 15 min interval, exposure was resumed for another three (or four?) cycles. Finally, starting at 38.5°C, exposure was performed until a lethal temperature of 42.8 ± 0.2°C was attained after another 30-35 min. |
| Measurand | Value | Type | Method | Mass | Remarks |
|---|---|---|---|---|---|
| power density | 60 mW/cm² | mean | measured | - | - |
| SAR | 14 W/kg | mean | estimated | - | [Durney et al., 1978] |
During intermittent exposure to an average power density of 60 mW/cm², doxapram significantly increased the time required for temperature to return to the pre-irradiation level. When irradiation was continued until death, doxapram administration caused no significant change in survival time when compared to saline controls. Thus, although the drug decreased thermoregulatory efficiency during intermittent radiofrequency exposure, no change in susceptibility to terminal radiofrequency exposure was observed. Although doxapram can cause hypothermia under certain conditions, the drug does not appear to be of value in cases of accidental radiofrequency exposure.
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