Noninvasive Continuous Arterial Blood Pressure Monitoring with Nexfin®

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 (R) (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 non-invasively and continuously using physiologic pressure reconstruction. Changes in pressure can be followed and values are comparable to invasive monitoring.