In Vitro Comparison of the New In-Line Monitor BMU 40 versus a Conventional Laboratory Analyzer

Abstract

Reliable information about different blood parameters is essential in maintaining hemodynamics, perfusion, and gas exchange during cardiopulmonary bypass (CPB). For this purpose, a precise and continuous monitoring is needed. The objective of this in vitro study was to compare a novel continuous in-line blood parameter monitoring system versus a reference laboratory analyzer. The study was conducted as an in vitro prospective experimental study during a CPB simulation. The reliability of BMU 40 was tested in monitoring the pO2, oxygen saturation (SO2), and hematocrit (Hct) under physiological and extreme conditions with regards to temperature, oxygenation, and blood concentration. Four different tests were performed and conducted with five sensors each. Correlation analyses and Bland-Altman analyses were performed. A total of 350 measurement points were compared. All monitored values of blood parameters correlated highly with laboratory values (all r values >.90). Test 1: Biases of pO2(act) varied from −3.24 mmHg (±6.86 mmHg) up to 6.0 mmHg (±17.89 mmHg). The biases of pO2(37°C) ranged from −3.52 mmHg (±6.01 mmHg) up to 68.8 mmHg (±67.82 mmHg). Test 2: The biases standard deviations (SD) for Hct ranged from −0.35% (±.79%) up to 2.35% (±.91%). The biases (SD) for SO2varied from −.45% (±.86%) up to .85% (±1.01%). Test 3: The biases (SD) of Hct ranged from −1.00% (±1.84%) up to −.67% (±1.49%). Test 4: The biases (SD) for SO2varied from −.36% (±1.60%) up to.48% (±.90%). The BMU 40 is a reliable device in measuring the partial oxygen pressure (pO2), SO2, and Hct under normal physiological and extreme conditions with regards to temperature, oxygenation, and blood concentration in simulation of CPB. The algorithm to calculate pO2(37°C) under hypothermic conditions needs to be adjusted. (Before the official market launch a new software version of the BMU 40 has been developed. The algorithm to calculate pO2(37°C) under hypothermic conditions has been improved and the miscalculation eliminated.)