Heat‐washout: a new method for measuring cutaneous blood flow rate in areas with and without arteriovenous anastomoses

Abstract

A new method, the heat-washout method, for measuring total cutaneous blood flow rate is introduced. The measurements were performed with a transcutaneous (tc) PO2-electrode that is capable of heating and measuring local temperature, and it is constructed with a thermostatically controlled cap. The probe was heated electrically to a selected temperature 2-10 degrees above normal skin temperature. When the temperature was stable, the heating element was turned off, and the temperature was registered every 10 s until a stable baseline temperature, Tb, was obtained. Tb was subtracted from the registered temperatures giving deltaTs that were plotted in a semilogarithmic diagram. The heat-washout was monoexponential, and the slope was used for calculating blood flow rate in accordance with the principle of Kety, using a known partition coefficient. The method was applied to the forearm in two subjects, and the results were compared to blood flow rates obtained simultaneously by the 133Xe-washout method in the same area. The equation of the regression line was y = 2.5 + 0 x 968X and the correlation coefficient was 0 x 986 at temperature levels of 37-45 degrees C. In the pulp of the thumb, blood flow rates, in arteriovenous anastomoses, were estimated in two subjects by subtracting the capillary blood flow rate, measured by 133Xe-washout, from the total cutaneous blood flow rate, measured by heat-washout. Due to a relatively low diffusions coefficient for 133Xe compared to heat, 133Xe cannot be used for measurement of blood flow rate in arteriovenous anastomoses.

Physiologically based pharmacokinetic modeling of arterial – antecubital vein concentration difference

“…al. [54], it was assumed that the tissue drained by the antecubital vein was mostly muscle with a blood flow of 0.045 ml/min/gm.…”

Physiologic measures of sexual function in women: a review

“…Subsequently, Levin and Wagner adapted the technique of Midttun et alto measure vaginal blood flow (the “wash-out method”) (29). The used a Radiometer heated electrode that was held against the vaginal surface and heated it to 41-43 degrees Celsius and then switched it off.…”

Heat‐washout measurements compared to distal blood pressure and perfusion in orthopaedic patients with foot ulcers

“…The interval for parameter estimation is started 1·5 min after heating is turned off T 1 (detected automatically after measured temperature decrease by >1% compared to maximum temperature) and for a washout period of 12 min ( T 2 = T 1 + 12 min) as recommended (Midttun et al ., ). If 12 min of measurements of heat washout is not available, it is continued until the end of the measuring period.…”

“…, Midttun et al ., ; Midttun & Snorgaard, ). Heat washout has previously been compared to 133 Xe washout, the gold standard for measuring cutaneous BFR, and a correlation coefficient of 0·968 was found (Midttun et al ., ). In this study, BFR measured by the heat‐washout method was compared to systolic toe and ankle blood pressure, and skin perfusion pressure in the calf and dorsal forefoot in orthopaedic patients with foot ulcers.…”