Temperature change in human muscle during and after pulsed short-wave diathermy

A time series design was used, with the dependent variable being gastrocnemius muscle temperature at a depth of 3 cm.

To determine the rate of temperature rise and the rate of post-treatment temperature decline in skeletal muscle following the application of pulsed short-wave diathermy (PSWD).

Data on PSWD rate and longevity of heating are 20 years old and outdated. With the recent introduction of advanced diathermy equipment, results of our study would provide clinicians with much needed information regarding treatment duration.

A 23-gauge thermistor was inserted into the center of the medial head of the anesthetized gastrocnemius muscle, 3 cm below the skin's surface of 20 subjects. The PSWD (27.12 MHz frequency) was applied using the following parameters: 800 bursts per second; 400 microseconds burst duration; 850 microseconds interburst interval; with a peak root mean square (RMS) amplitude of 150 W per burst and an average RMS output of 48 W. Temperature changes were documented every 5 minutes during the treatment and additionally at 5 and 10 minutes following treatment.

The average baseline and peak temperatures were 35.84 +/- 0.93 degrees C and 39.80 +/- 0.83 degrees C, respectively. Mean temperature increases were: 1.36 +/- 0.90 degrees C (5 min); 2.87 +/- 1.44 degrees C (10 min); 3.78 +/- 1.19 degrees C (15 min); 3.49 +/- 1.13 degrees C (20 min). After the treatment terminated, intramuscular temperature dropped 0.97 +/- 0.68 degree C in 5 minutes and 1.78 +/- 0.69 degrees C in 10 minutes.

PSWD is an effective modality if temperature elevation of deep tissue over a large area is the clinical objective.