PEAK CALF BLOOD-FLOW ESTIMATES ARE HIGHER WITH DOHN THAN WITH WHITNEYPLETHYSMOGRAPH

Estimates of calf blood flow with venous occlusion plethysmography var y widely between studies, perhaps due to the use of different plethysm ographs. Consequently, we compared calf blood flow estimates at rest a nd during reactive hyperemia in eight healthy subjects (four men and f our women) with two commonly used plethysmographs: the mercury-in-sila stic (Whitney) strain gauge and the Dohn air-filled cuff. To minimize technical variability, flow estimates were compared with a Whitney gau ge and a Dohn cuff on opposite calves before and after 10 min of bilat eral femoral arterial occlusion. To account for any differences betwee n limbs, a second trial was conducted in which the plethysmographs wer e switched. Resting flows did not differ between the plethysmographs ( P = 0.096), but a trend toward lower values with the Whitney was appar ent. Peak flows averaged 37% lower with the Whitney (27.8 +/- 2.8 ml . dl(-1) . min(-1)) than with the Dohn plethysmograph (44.4 +/- 2.8 ml . dl(-1) . min(-1); P < 0.05). Peak flow expressed as a multiple above baseline was also lower with the Whitney (10-fold) than with the Dohn plethysmograph (14.5-fold; P = 0.02). Across all flows at rest and du ring reactive hyperemia, estimates were highly correlated between the plethysmographs in all subjects (r(2) = 0.96-0.99). However, the mean slope for the Whitney-Dohn relationship was only 60 +/- 2%, indicating that over a wide range of flows the Whitney gauge estimate was 40% lo wer than that for the Dohn cuff. These results demonstrate that the sa me qualitative results can be obtained with either plethysmograph but that absolute flow values will generally be lower with Whitney gauges.