Study type: Medical/biological study (experimental study)

Effect of high-peak power pulses on isolated nerve function med./bio.

By: Pakhomov AG, Dubovick BV, Kolupayev VE, Pronkevich AN
Published in: Electro Magnetobiol 1993; 12 (1): 1-15
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Aim of study (acc. to author and editor)

To study the effects of nonthermal microwave electromagnetic fields on nerve function (compound action potential).

Background/further details

To carry out a detailed analysis of the nonthermal microwave effect dependence on modulation parameters, and to check Tigranyan's hypothesis.
Tigranyan found severe disturbances in nerve function if intense enough microwave pulses coincided with latent period of compound action potential (CAP) propagation (e.g. CAP amplitude diminished by 93-95 %, CAP velocity decreased by 35-40 %). Tigranyan proposed that microwave pulse energy converts into mechanical pulses, propagating in a spiral between Schwann cell membranes of the nerve sheath; because of the phase synchronism effect, this in turn evokes another pulse perpendicular to the nerve surface that is strong enough to damage the "active" nerve membrane.

Endpoint

Exposure

Exposure Parameters
Exposure 1: 915 MHz
Modulation type: pulsed
Exposure duration: continuous for 90 min
  • SAR: 72 kW/kg peak value (33-72 kW/kg)
  • SAR: 1.35 kW/kg mean (1.15-1.35 kW/kg)
Exposure 2: 915 MHz
Modulation type: pulsed
Exposure duration: continuous for 90 min
  • SAR: 13 kW/kg peak value (6-13 kW/kg)
  • SAR: 1.35 kW/kg mean (1.15-1.35 kW/kg)

Exposure 1

Main characteristics
Frequency 915 MHz
Type
Exposure duration continuous for 90 min
Modulation
Modulation type pulsed
Pulse width 0.5 ms
Repetition frequency 50 Hz
Pulse type rectangular
Exposure setup
Exposure source
  • stripline slot irradiator
Chamber The stripline irradiator and the experimental chamber were placed in an anechoic box. All the inputs to the box were shielded or filtered.
Setup The stripline slot irradiator consisted of two parallel metal strips on a dielectric base layer with the following dimensions: strip length 35.25 mm, width 2 mm, and thickness negligible. The distance between strips (slot) was 3.6 mm. An area of about 0.5 cm² near the end of the strips served as a bottom for the 0.2-ml bath provided with a fairly uniform field. The chamber was placed perpendicular to the slot to minimize irradiation of nerve sites situated in its lateral sections.
Sham exposure A sham exposure was conducted.
Additional info Nerves were stimulated using twin pulses separated by a 6-ms interval at a rate of 50 pairs/s. Microwave pulses were either synchronised with the stimuli in various manners or were asynchronous. The part of the nerve situated in the lateral chamber which was submerged into oil and out of the exposure zone served as control nerve site, and the other part which crossed the medial chamber filled with Ringer's solution served as exposed nerve site. For some sham exposed preparations, the saline was conventionally preheated by 3°C.
Parameters
Measurand Value Type Method Mass Remarks
SAR 72 kW/kg peak value measured - 33-72 kW/kg
SAR 1.35 kW/kg mean measured - 1.15-1.35 kW/kg
Measurement and calculation details

The SAR was calculated from the temperature difference and the velocity of the solution flowing in and out and the volume of the bath.

Exposure 2

Main characteristics
Frequency 915 MHz
Type
Exposure duration continuous for 90 min
Modulation
Modulation type pulsed
Pulse width 3 ms
Repetition frequency 50 Hz
Pulse type rectangular
Exposure setup
Exposure source
Sham exposure A sham exposure was conducted.
Parameters
Measurand Value Type Method Mass Remarks
SAR 13 kW/kg peak value measured - 6-13 kW/kg
SAR 1.35 kW/kg mean measured - 1.15-1.35 kW/kg

Exposed system:

Methods Endpoint/measurement parameters/methodology

Investigated system:
Time of investigation:
  • during exposure

Main outcome of study (acc. to author)

The exposed nerves underwent faster decrease of compound action potential amplitude and tracing integral; the effect was microwave-specific since the equivalent conventional heating of nerve produced the opposite changes. Compound action potential onset and peak velocities as well as nerve refractivity were not affected by microwave exposure. The severe disturbance of nerve function reported by Tigranyan were not detected, although the exposure conditions were the same.

Study character:

Study funded by

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