The impact of upper-limb position on estimated central blood pressure waveforms.

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Pulse wave analysis (PWA) utilizes arm blood pressure (BP) waveforms to estimate aortic waveforms. The accuracy of central BP waveform estimation may be influenced by assessment site local haemodynamics. This study investigated whether local haemodynamic changes, induced via arm tilting ±30° relative to heart level, affect estimated central systolic BP (cSBP) and arterial wave reflection (central augmentation index, cAIx; aortic backward pressure wave, Pb). In 20 healthy adults (26.7 years [SD 5.2], 10 F) brachial BP waveforms were simultaneously recorded on experimental and control arms. The experimental arm was randomly repositioned three times (heart level, -30° heart level, +30° heart level), while the control arm remained fixed at heart level. For the experimental arm, arm repositioning resulted in a large (partial eta-squared > 0.14) effect size (ES) change in SBP (ES = 0.75, P < 0.001), cSBP (ES = 0.81, P < 0.001), and cAIx (ES = 0.75, P = 0.002), but not Pb (ES = 0.06, P = 0.38). In the control arm, cAIx (ES = 0.22, P = 0.013) but not SBP or cSBP significantly changed. Change in experimental arm cSBP was partially explained by brachial systolic blood velocity (P = 0.026) and mean diameter (P = 0.012), while change in cAIx was associated with brachial retrograde blood velocity (P = 0.020) and beta stiffness (P = 0.038). In conclusion, manipulation of assessment site local haemodynamics, including the blood velocity profile and local arterial stiffness, had a large effect on estimated cSBP and cAIx, but not on Pb. These findings do not invalidate PWA devices but do suggest that the accuracy of the estimated aortic pressure waveform is dependent on stable peripheral haemodynamics.