A NEW NONINVASIVE STATISTICAL-METHOD TO ASSESS THE SPONTANEOUS CARDIAC BAROREFLEX IN HUMANS

1. A new method was developed to evaluate cardiac baroreflex sensitivi ty. The association of a high systolic blood pressure with a low heart rate or the converse is considered to be under the influence of cardi ac baroreflex activity, This method is based on the determination of t he statistical dependence between systolic blood pressure and heart ra te values obtained non-invasively by a Finapres device, Our computeriz ed analysis selects the associations with the highest statistical depe ndence, A 'Z-coefficient' quantifies the strength of the statistical d ependence, The slope of the linear regression, computed on these selec ted associations, is used to estimate baroreflex sensitivity. 2. The p resent study was carried out in 11 healthy resting male subjects, The results obtained by the 'Z-coefficient' method were compared with thos e obtained by cross-spectrum analysis, which has already been validate d in humans, Furthermore, the reproducibility of both methods was chec ked after 1 week. 3. The results obtained by the two methods were sign ificantly correlated (r=0.78 for the first and r=0.76 for the second e xperiment, P<0.01), When repeated after 1 week, the average results we re not significantly different, Considering individual results, test-r etest correlation coefficients were higher with the Z-analysis (r=0.79 , P<0.01) than with the cross-spectrum analysis (r=0.61, P<0.05). 4. I n conclusion, as the Z-method gives results similar to but more reprod ucible than the cross-spectrum method, it might be a powerful and reli able tool to assess baroreflex sensitivity in humans.