Comparison of reactive hyperemia in warm and cool human forearms over a range of ischemic periods.

The characteristics of reactive hyperemia in the warm human forearm are well documented but comparable data at lower temperatures are sparse. The present study was designed to examine reactive hyperemia in the forearms of 8 subjects using a range of ischemic periods of 0.5, 1, 2, 4, and 8 min at plethysmograph temperatures of 34 degrees and 14 degrees C. The peak flow rates and hyperemic volumes following all of the durations of ischemia were significantly lower at 14 degrees C. There was a proportional relationship between the hyperemic volume and the duration of ischemia at both temperatures. The difference noted in the magnitude of the responses at the two temperatures may be explained by a reduction in the rate of metabolism in the forearm at the lower temperature, but reduced vascular distensibility cannot be excluded.