Aortic Wave Reflection During Orthostatic Challenges: Influence of Body Position and Venous Pooling

William E Hughes; Darren P Casey

doi:10.1093/ajh/hpw138

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Aortic Wave Reflection During Orthostatic Challenges: Influence of Body Position and Venous Pooling

Journal article

Open access

Peer reviewed

Aortic Wave Reflection During Orthostatic Challenges: Influence of Body Position and Venous Pooling

William E Hughes and Darren P Casey

American journal of hypertension, Vol.30(2), pp.166-172

02/2017

DOI: 10.1093/ajh/hpw138

PMID: 28077421

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Abstract

Aortic wave reflection (augmentation index; AIx) decreases during orthostatic challenges despite increased peripheral resistance, which is thought to be due to venous pooling. The purpose of this study was to examine if the decrease in AIx during an orthostatic challenge is due to venous pooling alone or body position manipulation. Twenty-three young, healthy adults (11F/12M) participated in 3 separate orthostatic challenges (5 minutes each); 60° head-up tilt (HUT), 60° HUT with bilateral rhythmic blood pressure (BP) cuff inflation on calves (75 mm Hg) to minimize venous pooling, and lower body negative pressure (LBNP; -30 mm Hg) for venous pooling independent of body position. High-fidelity radial artery pressure waveforms using applanation tonometry were recorded at minutes 2:30 and 5:00 during each condition. Aortic BP and wave reflection were analyzed from a synthesized aortic BP waveform. Compared to resting (baseline) measurements, AIx did not significantly decrease at minutes 2:30 or 5:00 of HUT conditions (HUT 0 ± 2% vs. -3 ± 3%, 0 ± 2%; HUT w/cuffs 0 ± 2% vs. -4 ± 2%, 0 ± 2%). Conversely, LBNP substantially reduced AIx at minutes 2:30 and 5:00 (1 ± 2% vs. -15 ± 2% and -12 ± 2%; P < 0.01). When standardized to heart rate (AIx@75), AIx@75 increased relative to baseline during HUT conditions (P < 0.05). In contrast to previous studies, AIx did not decrease during passive HUT, yet decreased substantially during LBNP. Despite being well matched for peripheral hemodynamics, it appears that LBNP elicits a greater effect on central hemodynamics, relative to passive HUT. Collectively, changes in body position alone do not explain differences in AIx during orthostatic conditions.

Follow-Up Studies

Humans

Lower Body Negative Pressure - methods

Male

Arterial Pressure - physiology

Healthy Volunteers

Pulse Wave Analysis - methods

Hypertension - physiopathology

Young Adult

Rest

Posture - physiology

Vascular Stiffness - physiology

Electrocardiography

Heart Rate - physiology

Adult

Female

Exercise - physiology

Aorta - physiopathology

Hydroxyethylrutoside

Details

Title: Subtitle: Aortic Wave Reflection During Orthostatic Challenges: Influence of Body Position and Venous Pooling
Creators: William E Hughes - Department of Physical Therapy and Rehabilitation Science, Carver College of Medicine, University of Iowa, Iowa City, Iowa, USA
Darren P Casey
Resource Type: Journal article
Publication Details: American journal of hypertension, Vol.30(2), pp.166-172
Publisher: United States
DOI: 10.1093/ajh/hpw138
PMID: 28077421
ISSN: 0895-7061
eISSN: 1879-1905
Language: English
Date published: 02/2017
Academic Unit: Physical Therapy and Rehabilitation Science; Fraternal Order of Eagles Diabetes Research Center
Record Identifier: 9984047762302771

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