Effects of Various Body Positions on Arterial Stiffness as Assessed by Pulse Wave Velocity

Abstract

BackgroundStandard measurements of arterial stiffness via pulse wave velocity (PWV) are conducted with participants in the supine position. When participants cannot tolerate supine position for prolonged procedure time (e.g., low back pain), accommodations may be made to tilt the bed up or bend the knees (i.e., Fowler’s positions). Moreover, a new testing device (Vicorder) that uses neck oscillometric cuff requires upper body tilt to avoid jugular vein interference on the recorded carotid pulse. Accordingly, this study aimed to investigate the effect of varying body positions on arterial stiffness measured via PWV.METHODSA total of 70 adults (43 women) varying widely in age (19‐66 years old), race/ethnicity (41% non‐white), and medical conditions were studied. Both carotid‐femoral PWV (cfPWV) and brachial‐ankle PWV (baPWV) were measured using two different testing devices (Omron vp1000plus and Vicorder) with participants in the reference supine (0º) position, 10º, 20º, 30º, and 40º upper body tilted‐up positions with and without knee flexion. The presence of jugular vein interference was documented visually on the oscillometric arterial waveforms at each body angle.RESULTSBoth cfPWV and baPWV measured at 10º upper body tilt‐up position were not significantly different from those assessed at the reference supine (0º) position. Upper body angle of 20º or greater produced PWVs that were significantly and gradually elevated (p<0.01). The magnitude of elevations in cfPWV were 7% (95% CI [6‐11%]) at 20º and 15% (95% CI [11‐18%]) at 40º while the elevations in baPWV were 8% (95% CI [6‐10%]) at 10º and 33% (95% CI [30‐36%]) at 40º compared with the supine (0º) position. Knee flexion did not alter cfPWV compared with straight knees whereas knee flexion decreased baPWV at the same upper body angle (p<0.05). Jugular vein interference in the Vicorder device appeared on 78% of participants in the supine (0º) position and gradually decreased as the upper body angle increased, resulting in 7% of the participants at 30º angle. The appearance of Jugular vein contamination was not affected by knee flexion.CONCLUSIONArterial stiffness as assessed by cfPWV and baPWV increased gradually and significantly by the use of semi‐Fowler position of ≥20º whereas bending knees at each angle decreased baPWV, but did not appear to influence cfPWV. Our present findings highlight the difficulty in comparing two different devices that are supposed to reflect the same arterial property.