Abstract
Objective
The aim of the present study was to evaluate a simplified method for FRC measurement.Design: Accuracy and precision of the method were assessed in a physical lung model; reproducibility was tested in 10 mechanically ventilated patients. In each patient FRC was measured at three PEEP levels.Setting: Post-operative intensive care unit in a university hospital.
Measurements and results
Gas flow, CO2 concentration, and O2 concentration were measured during in- and expiration by pneumotachography, a mainstream capnometer and a sidertream O2-analyser. For FRC-measurement inspiratory O2 concentration was changed by 30%. FRC was determined as mean value of a N2 washout and N2 washin procedure. Evaluation of this method in a lung model shows a good correlation between FRC set in the lung model and FRC measured (FRC measured =1.028*FRC model+22.92 ml;r 2=0.957;n=30). The mean difference was 4.4% of FRC-reference (range −8.4% to +21.7%). Duplicate determinations in 10 mechanically ventilated patients differed by an average of −2.7% (range −30.1% to +27.3%).
Conclusion
Our results suggest that the proposed method can be used in daily clinical work.
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Fretschner, R., Deusch, H., Weitnauer, A. et al. A simple method to estimate functional residual capacity in mechanically ventilated patients. Intensive Care Med 19, 372–376 (1993). https://doi.org/10.1007/BF01724875
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DOI: https://doi.org/10.1007/BF01724875