REPRODUCIBILITY OF 3 DIFFERENT METHODS OF MEASURING BAROREFLEX SENSITIVITY IN NORMAL SUBJECTS

1. Baroreflex sensitivity is a useful tool for investigating cardiovas cular reflexes in a number of clinical settings. Several different met hods of measuring baroreflex sensitivity are available. In order to de termine a clinically useful non-invasive method of measuring barorefle x sensitivity we compared two methods (spectral analysis and the Valsa lva manoeuvre) with regard to reproducibility, agreement with a standa rd invasive method (phenylephrine infusion) and failure rate. 2. Twent y-six healthy subjects aged 22 to 63 years attended on three separate occasions for measurement of baroreflex sensitivity using the differen t methods. The effect of a recent head-up tilt on baroreflex sensitivi ty was measured.3. Reproducibility was best for the low-frequency comp onent of the spectral method [coefficient of variation 25.0% (range 3. 5-2.4%)] and worst for the Valsalva method [coefficient of variation 2 9.3% (range 13.8-93.1%)]. Both non-invasive methods overestimated valu es compared with the phenylephrine method [bias of low-frequency compo nent of the spectral method, 1.17 (0.38-3.6); bias of the Valsalva met hod, 1.13 (0.19-6.7)]. The high-frequency component of the spectral me thod did not agree with the phenylephrine method. 4. The spectral anal ysis method had the fewest failures (seven subjects with a failure on at least one occasion), and the phenylephrine method the most (16 subj ects with a failure on at least one occasion). A short head-up tilt di d not affect the subsequent non-invasive measurement of baroreflex sen sitivity. 5. It was concluded that the low-frequency component of the spectral method was the most clinically useful non-invasive measuremen t of baroreflex sensitivity.