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

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 (Cuff_CBP) to estimate central BP indices (systolic BP (SBP), diastolic BP (DBP), pulse pressure (PP), augmentation pressure (AP), augmentation index (AIx)) with noninvasive radial tonometry (Ton_CBP). METHODS Consecutive Cuff_CBP (SphygmoCor Xcel) and Ton_CBP (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 Cuff_CBP compared with Ton_CBP (8.58±19.06mm Hg, ICC 0.164, 95% CI -0.029 to 0.321). CONCLUSION cSBP, cDBP, and cPP derived from Cuff_CBP are substantially equivalent to Ton_CBP, although the level of agreement is dependent on calibration method. Further validity testing of Cuff_CBP by comparison with invasively measured central BP will be required.