title: No effect of Valsalva maneuver or Trendelenburg angle on axillary vein size.
abstract: BACKGROUND
  A new technique for establishing ultrasound-guided central access involves the use of the axillary vein, the distal projection of the subclavian vein, via the lateral chest.
  
  
  OBJECTIVE
  To examine the effects of Valsalva maneuver and Trendelenburg positioning on axillary vein cross-sectional area (CSA).
  
  
  METHODS
  Using a group-sequential design, we enrolled stable emergency patients and measured their axillary veins sonographically. Patients were measured while supine, then after a Valsalva maneuver, and then at 5°, 10°, 15°, and 17° of Trendelenburg positioning, pausing 2 min after each change. We asked patients to score their discomfort from 0 to 10 in each position.
  
  
  RESULTS
  We enrolled 30 adult patients with a median age of 39 years (range, 20-66 years). Treating physicians considered 11 of these patients to have hypovolemia. The Valsalva maneuver decreased CSA (Mean difference = -0.03 cm(2)), (95% confidence interval [CI] -0.10-0.04). Trendelenburg positioning did not statistically increase CSA. The 5° position caused the largest increase, that is, 0.04 cm(2) (95% CI -0.04-0.12) in the entire group and 0.1 cm(2) (95% CI -0.07-0.28) in the hypovolemic subgroup. At greater degrees of Trendelenburg positioning, patients reported higher discomfort scores or simply dropped out.
  
  
  CONCLUSIONS
  The Valsalva maneuver and Trendelenburg angles above 10° do not increase axillary vein area but do increase patient discomfort. Our data suggest optimal positioning in the supine resting position or at a 5° Trendelenburg position.
authors.affiliation: University of Pittsburgh Medical Center, Pittsburgh, Pennsylvania, USA.
authors.forename: Deanna R
authors.initials: DR
authors.lastname: Ford
authors.forename: Michael D
authors.initials: MD
authors.lastname: Witting
authors.forename: Milan V
authors.initials: MV
authors.lastname: Vora
authors.forename: Sarah K
authors.initials: SK
authors.lastname: Sommerkamp
authors.forename: Brian D
authors.initials: BD
authors.lastname: Euerle
mesh_terms: D000328:Adult; D000368:Aged; D001367:Axillary Vein / Q000033:anatomy & histology* / Q000000981:diagnostic imaging; D002405:Catheterization, Central Venous / Q000379:methods; D003430:Cross-Sectional Studies; D004636:Emergency Service, Hospital; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D056888:Patient Positioning; D018084:Ultrasonography, Interventional / Q000379:methods; D014636:Valsalva Maneuver; D055815:Young Adult
keywords: Valsalva maneuver; axillary vein; catheterization; central venous; head-down tilt; interventional; ultrasonography