title: Effect of positive external pressure on calf volume and local venous haemodynamics.
abstract: The pressure external to the calf was increased suddenly in 11 normal subjects and the resulting change in calf volume (considered to be mainly a change of calf vein blood volume) was followed using a mercury-in-rubber strain gauge. For a small increase of pressure the volume decreased exponentially and increased linearly when the pressure was suddenly released. A simple theory was developed which treats the calf veins as a single volume with a single compliance and a single outflow resistance. Using the theory, the following average results were obtained from measured values: effective venous compliance 1-1%kPa (SD 0.3); effective venous outflow resistance 3.8 s kPa/% (SD 1-3); and total flow into the veins from themicrocirculation 0.054%/s (SD 0.020) (% refers to a change in volume expressed as a percentage of the initial volume of the calf). The significance of the findings is considered with special reference to the occurrence of calf vein thrombosis.
mesh_terms: D000328:Adult; D001810:Blood Volume; D005260:Female; D006439:Hemodynamics; D006801:Humans; D007866:Leg / Q000098:blood supply*; D008297:Male; D008875:Middle Aged; D011312:Pressure; D013924:Thrombophlebitis / Q000209:etiology; D014680:Veins