Comparison of baroreflex sensitivity measures for assessing subjects with obstructive sleep apnea.

Baroreflex sensitivity (BRS) is assessed in subjects with and without obstructive sleep apnea (OSA) using the time domain direct sequence technique, the spectral transfer function (TF) technique and the alpha index technique. All three measures showed a significantly depressed BRS value in subjects with severe apnea. The high frequency (HF) component of the spectral measures showed higher correlation with the sequence technique measures than the low frequency (LF) component. The baroreceptor effectiveness index (BEI) showed a strong relationship with the HF coherence value from the spectral measures. All three BRS measures decreased with increasing heart rate. Heart rate correction of the sequence technique estimates to 60 beats per minute did not have a significant impact on the BRS estimates.