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Objective

To assess day-by-day variability of spontaneous baroreflex sensitivity (BRS) measurements, providing implications for their reliability in clinical and research studies.

Methods

Forty-four healthy volunteers and 57 patients with previous myocardial infarction (MI) underwent an 8+ 8 min (spontaneous+ paced breathing) recording of ECG and noninvasive arterial pressure on two consecutive days. BRS was computed according to the sequence method (BRS_seq), the original and modified transfer function method (BRS_TF and BRS_TF mod) and the alpha method (BRS_αLF and BRS_αHF). Absolute and relative reliability were assessed by the 95% limits of random variation (LoV) and by the intraclass correlation coefficient (ICC), respectively. The sample size needed to detect a clinically relevant change was also estimated.

Results

In healthy volunteers during spontaneous breathing, BRS_seq, BRS_TF …