Accuracy of a continuous blood pressure monitor based on arterial tonometry

A validation study of the continuous noninvasive tonometric blood pressure monitor called JENTOW was performed in 20 normotensive subjects and 10 hypertensive patients. Tonometric and intra-arterial blood pressures were simultaneously recorded at supine rest and during a Valsalva maneuver and tilting test. The results of the strict evaluation of the instrument's capacity for reproducing intra-arterial blood pressure were as follows: 1) The overall frequency response of the transcutaneous blood pressure-monitoring system based on arterial tonometry was flat, with negligible delay to intra-arterial blood pressure in the range of 0-5 Hz. 2) The largest discrepancy between intra-arterial and tonometric pressure waveforms was found at the early systolic phase; except for this phase, the tonometric waveform was almost equal to the intra-arterial waveform. 3) The beat-to-beat variability of tonometric pressure corresponded to that of intra-arterial pressure almost perfectly in the physiologically significant frequency range of 0-0.5 Hz. 4) During resting conditions, the averages of the systolic and diastolic values measured tonometrically corresponded well to those measured intra-arterially. 5) The changes in the between-method discrepancy of blood pressure values during the Valsalva maneuver were statistically significant but small (< 5 mm Hg). 6) No significant effect of postural tilting was found on the between-method discrepancy. We conclude that this method is clinically acceptable and reliable except for its limited capacity for recording the higher frequency intra-arterial waveform and for responding to the relatively rapid and large transient changes in blood pressure.