Background: If invasive measurement of arterial blood pressure is not warranted, finger cuff technology can provide continuous and noninvasive monitoring. Finger and radial artery pressures differ; Nexfin® (BMEYE, Amsterdam, The Netherlands) measures finger arterial pressure and uses physiologic reconstruction methodologies to obtain values comparable to invasive pressures.
Methods: Intra-arterial pressure (IAP) and noninvasive Nexfin arterial pressure (NAP) were measured in cardiothoracic surgery patients, because invasive pressures are available. NAP-IAP differences were analyzed during 30 min. Tracking was quantified by within-subject precision (SD of individual NAP-IAP differences) and correlation coefficients. The ranges of pressure change were quantified by within-subject variability (SD of individual averages of NAP and IAP). Accuracy and precision were expressed as group average ± SD of the differences and considered acceptable when smaller than 5 ± 8 mmHg, the Association for the Advancement of Medical Instrumentation criteria.
Results: NAP and IAP were obtained in 50 (34–83 yr, 40 men) patients. For systolic, diastolic, mean arterial, and pulse pressure, median (25–75 percentiles) correlation coefficients were 0.96 (0.91–0.98), 0.93 (0.87–0.96), 0.96 (0.90–0.97), and 0.94 (0.85–0.98), respectively. Within-subject precisions were 4 ± 2, 3 ± 1, 3 ± 2, and 3 ± 2 mmHg, and within-subject variations 13 ± 6, 6 ± 3, 9 ± 4, and 7 ± 4 mmHg, indicating precision over a wide range of pressures. Group average ± SD of the NAP-IAP differences were −1 ± 7, 3 ± 6, 2 ± 6, and −3 ± 4 mmHg, meeting criteria. Differences were not related to mean arterial pressure or heart rate.
Conclusion: Arterial blood pressure can be measured noninvasively and continuously using physiologic pressure reconstruction. Changes in pressure can be followed and values are comparable to invasive monitoring.