Clinical validation of a continuous non-invasive haemodynamic monitor (CNAP™ 500) during general anaesthesia

Abstract

Background: We conducted a prospective study to test the validity of a new continuous non-invasive blood pressure (NIBP) monitor (CNAP) (CNAP™ Monitor 500). Methods: One hundred patients undergoing elective surgery under general anaesthesia were included in the study after informed written consent. The CNAP finger cuffs were placed on the fingers of one arm, an arterial catheter was inserted into the same arm and data were recorded simultaneously. Agreement between invasive arterial pressure (IAP) and blood pressure obtained by CNAP was compared using the BlandAltman method for repeated measurements. The data from the first 50 patients (software V3.0) were used to improve the software of the CNAP (software V3.5), which was then evaluated in another 50 patients. We defined a clinically acceptable agreement according to the standards of the American Association for the Advancement of Medical Instrumentation for NIBP measurements [limits of agreement (LOA) ±15 mm Hg]. Results: We analysed 524 878 paired measurements in 100 patients. The mean bias of the mean arterial pressure in the first 50 patients was -2.9 mm Hg (sd 10.6 mm Hg, LOA -23.7 to 17.9 mm Hg), and in the consecutive 50 patients (using software V3.5) the bias was -3.1 mm Hg (sd 9.5 mm Hg, LOA -21.6 to 15.4 mm Hg). Conclusions: The new CNAP monitor showed an agreement with the IAP that is promising but did not match our predefined criteria. © 2012 The Author. Published by Oxford University Press on behalf of the British Journal of Anaesthesia. All rights reserved.