SPONTANEOUS SKIN TEMPERATURE OSCILLATIONS IN NORMAL HUMAN-SUBJECTS

A noninvasive method based on high-resolution measurements and bandpas s filtering of spontaneous skin temperature oscillations (similar to 4 .0 x 10(-2)degrees C) in the low-frequency range (0.01-0.04 Hz) was in vestigated in normal human subjects. We hypothesized that the oscillat ions (temperature variability) originate from vasomotor activity of sm all arteries and arterioles in subcutaneous tissues. To test this hypo thesis, continuous blood pressure waveforms were obtained with the use of an external piezoelectric sensor. The peak-to-peak envelope of the pressure signal (pressure variability) was used as an indicator of va somotor activity. The variabilities of temperature and pressure were c ompared using cross-spectral and coherence analysis. The correlation b etween the peak frequency of the signals was 0.92, and the coherence w as greater than 0.9. The signals demonstrated similar changes in spect ral energy and peak frequency in response to mental stress. Reproducib ility of the temperature variability in individual subjects was verifi ed by repeating measurements 1-12 wk later. The differences in peak fr equency were small (0.0155 +/- 0.001 Hz), and in each subject the sign als exhibited similar patterns in response to stress. Correlation betw een spectral characteristics of the signals suggests that temperature variability can be attributed to changes in blood flow resulting from oscillations in vasomotor smooth muscle tone.