Evaluation of blood pressure and baroreflex sensitivity by radial artery tonometry versus finger arteriolar photoplethysmography

Background: Published normative data of noninvasive blood pressures (BPs) and autonomic modulations have been primarily derived from the finger arteriole using the Finapres (Ohmeda Co., Englewood, CO), a device that is no longer manufactured. Currently, beat-to-beat BP are obtained from the radial artery using the Colin tonometer. Methods: We compared BP and autonomic parameters in a crossover design between the two devices in 29 subjects during seated rest and a 0.1-Hz breathing protocol. In addition, we tested whether finger arteriolar BP differences were due to pressure changes exerted by the radial tonometer. Results: Uniformly, BP measured at the radial artery were significantly higher than those from the finger arteriole. Radial BP (106 ± 19.5 mm Hg) were higher than finger arteriolar BP (95.8 ± 13.7 mm Hg) (P < .005). Tonometric baroreflex sensitivity (BRS) (24.0 ± 18 msec/mm Hg) was higher compared to photoplethysmographic BRS (12.0 ± 7.7 msec/mm Hg; P < .0003). Systolic BP (radial artery) (115 ± 25 mm Hg) were higher compared to finger arteriolar BP (97.7 ± 19 mm Hg; P < .0025) during breathing, as was BRS (25.9 ± 11.6 msec/mm Hg v 21.5 ± 11.6 msec/mm Hg; P < .05). Differences in the low frequency systolic BP (LF_SBP), representative of sympathetic vasomotor modulation, between the two methods, whether absolute, normalized, or log-transformed were not observed. Conclusions: There were no differences in arteriolar BP values in the presence or absence of radial artery tonometric pressure. These findings indicate that differences exist in systolic BP and BRS using the tonometer (radial artery) versus the Finapres (Ohmeda Co.) (finger arteriole). Furthermore, these differences are not due to pressure exerted by the radial artery tonometer that supplies blood to the finger arteriole.