title: Comparison of passive leg raising and hyperemia on macrovascular and microvascular responses.
abstract: Passive leg raising is a simple diagnostic maneuver that has been proposed as a measure of arterial vasodilator reserve and possibly endothelial function. While passive leg raising has previously been shown to lower blood pressure, increase flow velocity and cause brachial artery dilation, its effects on microvascular flow has not been well studied. Also, passive leg raising has been directly compared previously to upper arm but never to lower arm occlusion of blood flow induced hyperemia responses. We compared changes in macrovascular indices measured by brachial artery ultrasound and microvascular perfusion measured by Laser Doppler Flowmetry induced by passive leg raising to those provoked by upper arm and lower arm induced hyperemia in healthy subjects. Upper arm induced hyperemia increased mean flow velocity by 398%, induced brachial artery dilatation by 16.3%, and increased microvascular perfusion by 246% (p<.05 for all). Lower arm induced hyperemia increased flow velocity by 227%, induced brachial artery dilatation by 10.8%, and increased microvascular perfusion by 281%. Passive leg raising increased flow velocity by 29% and brachial artery dilatation by 5.6% (p<.05 for all), but did not change microvascular perfusion (-5%, p=ns). In conclusion, passive leg raising increases flow velocity orders of magnitude less than does upper arm or lower arm induced hyperemia. Passive leg raising-induced brachial artery dilatation is less robust than either of these hyperemic techniques. Finally, although upper arm and lower arm hyperemia elicits macrovascular and microvascular responses, passive leg raising elicits only macrovascular responses.
authors.affiliation: Division of Cardiovascular Medicine, State University of New York Downstate Medical Center, Brooklyn, NY 11203-2098, USA.
authors.forename: Manasi
authors.initials: M
authors.lastname: Bapat
authors.forename: Daniel
authors.initials: D
authors.lastname: Musikantow
authors.forename: Kseniya
authors.initials: K
authors.lastname: Khmara
authors.forename: Priya
authors.initials: P
authors.lastname: Chokshi
authors.forename: Neel
authors.initials: N
authors.lastname: Khanna
authors.forename: Sean
authors.initials: S
authors.lastname: Galligan
authors.forename: Haroon
authors.initials: H
authors.lastname: Kamran
authors.forename: Louis
authors.initials: L
authors.lastname: Salciccioli
authors.forename: Frank C
authors.initials: FC
authors.lastname: Barone
authors.forename: Jason M
authors.initials: JM
authors.lastname: Lazar
mesh_terms: D000328:Adult; D001132:Arm / Q000098:blood supply; D001783:Blood Flow Velocity; D001808:Blood Vessels / Q000502:physiology*; D001916:Brachial Artery / Q000000981:diagnostic imaging / Q000502:physiology; D005260:Female; D006801:Humans; D006940:Hyperemia / Q000503:physiopathology*; D017078:Laser-Doppler Flowmetry; D007866:Leg / Q000098:blood supply*; D008297:Male; D008833:Microcirculation / Q000502:physiology*; D055806:Microvessels / Q000502:physiology; D009043:Motor Activity; D052580:Muscle Stretching Exercises; D026201:Musculoskeletal Manipulations; D010477:Perfusion; D014463:Ultrasonography; D014664:Vasodilation / Q000502:physiology*; D055815:Young Adult