MID-TERM AND LONG-TERM REPRODUCIBILITY OF NONINVASIVE MEASUREMENTS OFSPONTANEOUS ARTERIAL BAROREFLEX SENSITIVITY IN HEALTHY-VOLUNTEERS

Baroreflex sensitivity (BRS) is altered in a variety of circumstances and could be considered as a marker for the prognosis of some cardiova scular diseases. The present study was designed to evaluate the reprod ucibility of noninvasive measures of BRS, both at mid- and at long-ter m. Fourteen healthy volunteers were examined on three occasions (first interval = 1 week, second interval = 1 year). Each recording was perf ormed using a noninvasive photoplethysmographic device (Finapres 2300, Ohmeda), both in supine and standing positions. Two different methods of measurement were used: the sequences method and cross spectral ana lysis. The reproducibility of BRS measures was as satisfactory at mid- as at long-term for the sequences method (intraclass coefficient [ICC ] = 0.87 and 0.86, respectively), but it was better at mid- than at lo ng-term for the cross-spectral analysis (ICC = 0.85 and 0.54, respecti vely). The measures performed in standing position were obviously more reproducible than those made in recumbent position (ICC = 0.87 and 0. 70 for the sequences method, 0.85 and 0.71 for the cross-spectral anal ysis, respectively). Due to the high reproducibility of these noninvas ive measures, the number of patients to be included in a pharmacologic al study was calculated as rather small: for example, only 20 patients are required for detecting a change in upright BRS of 3 msec/mm Hg, a t long-term (sequences method). Likewise, the magnitude of the regress ion to the mean, which has to be expected in patients selected for a f ollow-up study, turned out to be low: for example, <15% of the differe nce between the patient group mean value and the reference value, both at mid- and at long-term (standing position, sequences method). We co nclude that: 1) The noninvasive measures of BRS in standing position a re reproducible enough to allow longitudinal studies to be conducted o ver either a short or a long period; 2) The long-term reliability of t he sequences method seems to be higher than that of the cross-spectral analysis; and 3) Subtle changes in SBR may be noninvasively detected within small patient groups. (C) 1997 American Journal of Hypertension , Ltd.