Background: Computerized, yet portable, bedside pulmonary monitors that can measure work of breathing (WOB) are now commercially available; however, none accurately measures WOB. The purpose of this study was to evaluate new software designed to measure WOB by means of the Campbell diagram and to test the agreement between a monitor (Model CP-100, Bicore, Irvine CA) programmed with the new software and the conventional method of measuring WOB.
Materials & methods: Using a lung model of our own devising, we compared WOB measurements between the monitor and conventional laboratory equipment. Inspiratory flow-rate, tidal volume (VT), and resistance of the model were adjusted to produce WOB ranging from 0.80 to 3.25 J/L. Regression analysis and calculation of bias and precision were performed for these data.
Results: For total, elastic, and resistive WOB, the two methods of measurement correlated strongly and positively. For all values of WOB, the correlation coefficients (r) and coefficients of determination (r2) were close to 0.99 (p < 0.0001); bias was minimal (-0.05 J/L) and precision acceptable (0.06 J/L).
Conclusion: Data from a lung model reveal that a respiratory monitor programmed with appropriate software can accurately measure total, elastic, and resistive WOB. The monitor may eventually prove useful for clinically assessing WOB, which then can be used to adjust the ventilator to optimize respiratory muscle loads.