title: Position modifies carotid artery blood flow velocity during straining.
abstract: The Valsalva maneuver (VM) produces rapid shifts in cerebrovascular blood flow and is often implicated in aneurysm rupture and rebleeding. To determine whether intensity of hemodynamic shifts is affected by position, we examined effects of five body positions (chair, 70 degrees and 30 degrees upright, flat, side) on carotid artery blood flow velocity (CABFV) across the VM in 141 healthy adults (30-55 yrs.). Subjects strained at 40 mmHg pressure for 10 seconds. CABFV was measured continuously by ultrasonic Doppler technique. During straining, position significantly (F = 13.7; p less than .0001) affected CABFV. Less reduction occurred in the chair (p less than .05) position than in any of the others. The 70 degrees position produced less fall in CABFV (p less than .05) than did the 30 degrees, flat and side positions. Less increase in CABFV across the VM was recorded in the chair position (p less than .05) than in any of the others. It is concluded that the chair position can be used therapeutically to reduce severe shifts of CABFV associated with straining.
authors.affiliation: School of Nursing, University of Michigan, Ann Arbor 48109.
authors.forename: B
authors.initials: B
authors.lastname: Therrien
mesh_terms: D000328:Adult; D001510:Bed Rest; D001783:Blood Flow Velocity; D002339:Carotid Arteries / Q000502:physiology*; D002560:Cerebrovascular Circulation / Q000502:physiology; D005260:Female; D006439:Hemodynamics; D006801:Humans; D008297:Male; D008875:Middle Aged; D011187:Posture; D014465:Ultrasonics; D014636:Valsalva Maneuver / Q000502:physiology*