Effects of gravity-induced upper-limb blood pressure changes on wave transmission and arterial radial waveform.

BACKGROUND: Local blood pressure (BP) changes induced by arm tilting may influence pressure wave transmission and reflection. We investigated the effects of upper-limb tilting on radial augmentation index (rAIx) and related central measures [aortic augmentation index (aAIx)]. METHODS: In 45 volunteers (age 49 ±â€Š19 years), supine brachial BP and radial artery waveforms were obtained by applanation tonometry with the dominant arm stretched and gently supported in three different positions: at the heart level, with the BP cuff 15 cm above heart level (approximately +30°), and 15 cm below heart level (-30°). RESULTS: Brachial SBP/DBP was 120/68 ±â€Š17/8 mmHg. Mean arterial pressure changed predictably with arm tilting (99 ±â€Š12 mmHg at -30°, 88 ±â€Š10 mmHg at 0°, 77 ±â€Š11 mmHg at +30°, all P < 0.001). rAIx decreased at -30° (69 ±â€Š22%), and increased at +30° (93 ±â€Š20%) compared with 0° (82 ±â€Š20%, all P less than 0.001). Changes in rAIx (value at +30° minus value at -30°) showed an inverse relationship with age (r = -0.32, P = 0.03). Heart rate, BP and rAIx did not change in the contralateral arm, which was held at the heart level during the examination. aAIx followed the same pattern as rAIx (123 ±â€Š27% at -30°, 144 ±â€Š33% at +30°, 136 ±â€Š31% at 0°, all P less than 0.001); changes in rAIx and aAIx were strongly related each other (r = 0.82, P < 0.001). CONCLUSION: Acute gravitational upper-limb BP changes generate opposite, profound changes in rAIx, and major artifactual changes in aAIx. These findings provide a rationale for recommending to keep the upper limb at the heart level during radial waveform assessment.