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Accuracy and precision of a new, portable, handheld blood gas analyzer, the IRMA
1Department of Anesthesiology, University of Michigan Medical School, Ann Arbor, USA.
Objective:
The accuracy and precision of the new IRMA (Immediate Response Mobile Analysis System, Diametrics, Inc., St. Paul, MN) handheld blood gas analyzer was compared with that of two benchtop blood gas analyzers. The IRMA consists of a notebook-sized machine and disposable cartridges, each containing a pH, a CO2 and an O2 electrode, and provides bedside (point-of-care) blood gas analysis.
Methods:
A total of 172 samples (arterial and mixed venous) were obtained from 25 informed, consenting patients undergoing cardiopulmonary bypass. The pH, PCO2 and PO2 of each sample was determined on four blood gas analyzers: NOVA Statlabs Profile 5 (NOVA Biomedical, Waltham, MA), the ABL-50 (Radiometer, West Lake, OH), and two IRMA machines. Linear regression and bias +/- precision were determined, comparing each of the analyzers with the NOVA.
Results:
All three machines showed a similar, high degree of correlation with the NOVA for pH, PCO2, and PO2. The bias and precision of the IRMA machines compared with the NOVA was similar to that of the ABL compared with the NOVA for pH (NOVA:ABL -0.005 +/- 0.011; NOVA:IRMA 1 = 0.0026 +/- 0.025; NOVA:IRMA 2 = 0.0021 +/- 0.025), for PCO2 (NOVA:ABL = -1.4 +/- 1.3 mmHg; NOVA: IRMA 1 = -1.3 +/- 1.9 mmHg; NOVA: IRMA 2 = -1.2 +/- 2.1 mmHg) and PO2 (NOVA:ABL = 3.6 +/- 21.1 mmHg; NOVA:IRMA 1 = 3.4 +/- 19.9 mmHg; NOVA:IRMA 2 = 6.3 +/- 20.9 mmHg). The bias found for pH, PCO2, and PO2 was not affected by extremes of temperature (range 25.5-40 degrees C) or hematocrit (range 11-44%) for any machine.
Conclusions:
The new technology incorporated in the IRMA blood gas analyzer provides results with an accuracy that is similar to that of benchtop analyzers, but with all of the advantages of point-of-care analysis.