Effect of temperature on digital systolic pressures in lower limb in arterial disease.

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Abstract
BACKGROUND: Toe pressures correlate with the chances of healing of skin lesions and with the risk of amputation and mortality. They are not affected by incompressibility of the tibial vessels, which may render ankle pressures inaccurate and reflect the overall arterial obstruction down to the digits. Digital pressures, however, may be affected by temperature. METHODS AND RESULTS: Measurements under routine laboratory conditions were compared with those at controlled temperatures in 77 limbs with arteriosclerosis obliterans. The desired local temperatures were attained by perfusing water through the cuffs for 7 minutes before the measurements while the flow was interrupted by a tourniquet to allow equilibration of the toe and water temperatures. Mean toe pressure of 34 +/- 4 mm Hg at 10 degrees C was significantly lower (p less than 0.001) than the values during routine measurements (57 +/- 4 mm Hg) and at 30 degrees C (69 +/- 4 mm Hg). The pressure at 30 degrees C was 10 +/- 3 mm Hg higher than during routine measurements when initial digit temperature was below 30 degrees C (p less than 0.01) but not when it was higher. Measurements at 3 degrees C increments from 27 degrees C to 39 degrees C showed progressive increase in pressure (p less than 0.01). CONCLUSIONS: Pressures at 36 degrees C and 39 degrees C were the highest but were not significantly different from each other. When toe temperature is low under routine conditions, the measured pressure may be falsely low, probably because of an effect on the main digital arteries that leads to delayed opening during deflation of the cuffs. Measurements at warm local temperature will increase the accuracy of the assessment of the severity of the arterial obstruction and may improve prediction of spontaneous healing of skin lesions.