Noninvasive measurement of baroreflex sensitivity index using an indirect and continuous blood-pressure recorder

The index of the baroreceptor reflex sensitivity (BRS) was measured noninvasively by monitoring the arterial pressure (AP) of the finger and R-R interval on the ECG during a Valsalva maneuver. An indirect finger AP measurement system was newly designed on the basis of the so-called vascular unloading technique. The BRS index was determined as the slope of the linear regression equation between the R-R interval and the virtual brachial AP which was evaluated from the finger AP. The data on both parameters were taken from the second period of the fourth phase in the Valsalva maneuver. The measurement was carried out on 24 inpatients (29-65 years) with essential hypertension. The conventional invasive method using phenylephrine or nitroglycerine was also performed on the same subjects. The correlation coefficient between the invasive and noninvasive methods was 0.81 when phenylephrine was used and 0.90 with nitroglycerine (p less than 0.001). The present method was found useful in routine clinical examination because of its easy and repeatable noninvasive application to patients without causing stress.