Reproducibility of strain gauge venous occlusion plethysmography in long-run measurements in man.

In order to evaluate strain gauge venous occlusion plethysmography as a tool to test the effects of treatment on peripheral blood flow, some biasing effects due to this technique were studied in relation to a long-run session and to cuff and gauge displacement. Arm peripheral blood flow was estimated by a computerized procedure during three successive days in a young male subject. The measurements were arranged as follows: 1) 75 replications under constant conditions, lasting 1.6 hours; 2) 18 triplets with alternative cuff displacement between two forearm positions, lasting 1.5 hours; 3) 40 measurements taken alternatively with a fixed gauge and a displaced one from a proximal to a distal position and vice versa, lasting 2.1 hours. Statistical comparison revealed: 1) a good long-run reproducibility during the first session; 2) a significant difference between the first and third day sessions under the same conditions; 3) a significant difference between the distal and proximal cuff mean flows during the second day session; 4 significant differences among the third day means in dependence of gauge position; 5) no significant dependence on strain gauge tension during the third day session. It is thus concluded that strain gauge plethysmography may be a reliable technique mainly in a longitudinal experimental design when the acute effect of some drug administration is to be evaluated.