ClearSight™ finger cuff versus invasive arterial pressure measurement in patients with body mass index above 45kg/m2

BackgroundMeasuring blood pressure in patients with obesity is challenging. The ClearSight (TM) finger cuff (FC) uses the vascular unloading technique to provide continuous non-invasive blood pressure measurements. We aimed to test the agreement of the FC with invasive radial arterial monitoring (INV) in patients with obesity.MethodsParticipants had a body mass index (BMI) >= 45kg/m(2) and underwent laparoscopic bariatric surgery. FC and INV measurements were obtained simultaneously every 5min on each patient, following induction of anesthesia. Agreement over time was assessed using modified Bland-Altman plots and error grid analysis permitted clinical interpretation of the results. Four-quadrant plots allowed assessment of concordance in blood pressure changes.ResultsThe 30 participants had a median (IQR) BMI of 50.2kg/m(2) (IQR 48.3-55.3). The observed bias (SD, 95% limits of agreement) for systolic blood pressure (SBP) was 14.3mmHg (14.1, -13.4 - 42.0), 5.2mmHg (10.9, -16.0 - 26.5) for mean arterial pressure (MAP) and 2.6mmHg (10.8, -18.6 - 23.8) for diastolic blood pressure (DBP). Error grid analysis showed that the proportion of readings in risk zones A-E were 90.8, 6.5, 2.7, 0 and 0% for SBP and 91.4, 4.3, 4.3, 0 and 0% for MAP, respectively. Discordance occurred in <= 8% of pairs for consecutive change in SBP, MAP and DBP.ConclusionsThe vascular unloading technique was not adequately in agreement with radial arterial monitoring. Evaluation in a larger sample is required before recommending this technique for intraoperative monitoring of patients with BMI >= 45kg/m(2).