title: Calf venous compliance measured by venous occlusion plethysmography: methodological aspects.
abstract: OBJECTIVE
  Calf venous compliance (C calf) is commonly evaluated with venous occlusion plethysmography (VOP) during a standard cuff deflation protocol. However, the technique relies on two not previously validated assumptions concerning thigh cuff pressure (P cuff) transmission and the impact of net fluid filtration (F filt) on C calf. The aim was to validate VOP in the lower limb and to develop a model to correct for F filt during VOP.
  
  
  METHODS
  Strain-gauge technique was used to study calf volume changes in 15 women and 10 age-matched men. A thigh cuff was inflated to 60 mmHg for 4 and 8 min with a subsequent decrease of 1 mmHg s(-1). Intravenous pressure (P iv) was measured simultaneously. C calf was determined with the commonly used equation [Compliance = β 1 + 2β 2 × P cuff] describing the pressure-compliance relationship. A model was developed to identify and correct for F filt.
  
  
  RESULTS
  Transmission of P cuff to P iv was 100 %. The decrease in P cuff correlated well with P iv reduction (r = 0.99, P < 0.001). Overall, our model showed that C calf was underestimated when F filt was not accounted for (all P < 0.01). F filt was higher in women (P < 0.01) and showed a more pronounced effect on C calf compared to men (P < 0.05). The impact of F filt was similar during 4- and 8-min VOP.
  
  
  CONCLUSIONS
  P cuff is an adequate substitute for P iv in the lower limb. F filt is associated with an underestimation of C calf and differences in the effect of F filt during VOP can be accounted for with the correction model. Thus, our model seems to be a valuable tool in future studies of venous wall function.
authors.affiliation: Department of Medical and Health Sciences, Linköping University, 581 85, Linköping, Sweden, johan.skoog@liu.se.
authors.forename: Johan
authors.initials: J
authors.lastname: Skoog
authors.forename: Helene
authors.initials: H
authors.lastname: Zachrisson
authors.forename: Marcus
authors.initials: M
authors.lastname: Lindenberger
authors.forename: Mikael
authors.initials: M
authors.lastname: Ekman
authors.forename: Lea
authors.initials: L
authors.lastname: Ewerman
authors.forename: Toste
authors.initials: T
authors.lastname: Länne
mesh_terms: D001794:Blood Pressure; D003627:Data Interpretation, Statistical; D005260:Female; D006801:Humans; D007866:Leg / Q000098:blood supply*; D008297:Male; D008955:Models, Cardiovascular; D010991:Plethysmography / Q000379:methods; D011312:Pressure; D012039:Regional Blood Flow; D014680:Veins / Q000502:physiology*; D055815:Young Adult