The Accuracy and Reliability of Non-Invasive Haemoglobin Measurements in the Emergency Room: a Small Prospective Observational Quality Control Study from a Swiss University Hospital ED

Abstract

Background: The accuracy and reliability of non-invasive oximetry for haemoglobin measurements were reported in operating rooms and intensive care units, though few studies evaluated this technology in emergency departments. The purpose of this study was to evaluate the accuracy and reliability of non-invasive SpHb readings from a portable device, in emergency department patients, compared to synchronous LabHb measurements. The authors sought to minimise external variables that could influence device performance, including learning curves and patient conditions, thus performed measurements by one trained user on stable adults only. Methods: The authors enrolled 24 consecutive adults admitted to the emergency department suspected or manifest active bleeding, and excluded cases of incarceration, pregnancy and burns. Haemoglobin concentrations were synchronously measured by phlebotomy laboratory analysis (LabHb) and using non-invasive readings (SpHb) from a portable Pronto-7 Pulse CO-Oximeter. Results: The non-invasive SpHb concentrations were recorded in 24 patients (100%), but the device it aborted during one or more measurement in 8 patients (33.3%) due to tremor and shivering. Paired comparison of SpHb and LabHb revealed a mean absolute error of 1.2 ± 1.3 g/dL (median 0.7, range 0.1 to 0.5), which equates to relative error of 9% ± 14% (median 5%, range 1% to 59%). Conclusions: Non-invasive SpHb measurements deviate from the ‘gold standard’ LabHb by an average of 1.2 g/dL (10%), but that outliers could be up to 5.2 g/dL (59%), which could lead to conflicting clinical decisions. Furthermore, the device functioned correctly in only 16 of 24 patients (66.6%), which should be reviewed in the light of difficult emergency department settings.