Non-invasive oscillometric versus invasive arterial blood pressure measurements in critically ill patients:A post hoc analysis of a prospective observational study

PURPOSE: The aim was to compare non-invasive blood pressure measurements with invasive blood pressure measurements in critically ill patients. METHODS: Non-invasive blood pressure was measured via automated brachial cuff oscillometry, and simultaneously the radial arterial catheter-derived measurement was recorded as part of a prospective observational study. Measurements of systolic arterial pressure (SAP), diastolic arterial pressure (DAP), and mean arterial pressure (MAP) were compared using Bland-Altman and error grid analyses. RESULTS: Paired measurements of blood pressure were available for 736 patients. Observed mean difference (±SD, 95% limits of agreement) between oscillometrically and invasively measured blood pressure was 0.8 mmHg (±15.7 mmHg, -30.2 to 31.7 mmHg) for SAP, -2.9 mmHg (±11.0 mmHg, -24.5 to 18.6 mmHg) for DAP, and -1.0 mmHg (±10.2 mmHg, -21.0 to 18.9 mmHg) for MAP. Error grid analysis showed that the proportions of measurements in risk zones A to E were 78.3%, 20.7%, 1.0%, 0%, and 0.1% for MAP. CONCLUSION: Non-invasive blood pressure measurements using brachial cuff oscillometry showed large limits of agreement compared to invasive measurements in critically ill patients. Error grid analysis showed that measurement differences between oscillometry and the arterial catheter would potentially have triggered at least low-risk treatment decisions in one in five patients.