Comparison of central blood pressure estimated by a cuff-based device with radial tonometry

Abstract

BACKGROUND New techniques that measure central blood pressure (BP) using an upper arm cuff-based approach require performance assessment. The aim of this study was to compare a cuff-based device (CuffCBP) to estimate central BP indices (systolic BP (SBP), diastolic BP (DBP), pulse pressure (PP), augmentation pressure (AP), augmentation index (AIx)) with noninvasive radial tonometry (TonCBP). METHODS Consecutive CuffCBP (SphygmoCor Xcel) and TonCBP (SphygmoCor 8.1) duplicate recordings were measured in 182 people with treated hypertension (aged 61±7 years, 48% male). Agreement between methods was assessed using standard calibration with brachial SBP and DBP (measured with the Xcel device), as well as with brachial mean arterial pressure (MAP; 40% form factor method) and DBP. RESULTS The mean difference ± SD for central SBP (cSBP), central DBP (cDBP), and central PP (cPP) between methods were -0.89±3.48mm Hg (intra-class correlation (ICC) 0.977; 95% confidence interval (CI) 0.973-0.982), -0.50±1.54mm Hg (ICC 0.992, 95% CI 0.987-0.993), and -0.42±3.57mm Hg (ICC 0.966, 95% CI 0.958-0.972), indicating good agreement. Wider limits of agreement were observed for central AP (cAP) and central AIx (cAIx) (-0.91±5.31mm Hg; ICC 0.802; 95% CI 0.756-0.839, -0.99±10.91%; ICC 0.749; 95% CI 0.691-0.796). Re-calibration with brachial MAP and DBP resulted in an overestimation of cSBP with CuffCBP compared with TonCBP (8.58±19.06mm Hg, ICC 0.164, 95% CI -0.029 to 0.321). CONCLUSION cSBP, cDBP, and cPP derived from CuffCBP are substantially equivalent to TonCBP, although the level of agreement is dependent on calibration method. Further validity testing of CuffCBP by comparison with invasively measured central BP will be required.