Evaluation of the Respiradyne Pulmonary Function Monitor

We evaluated the accuracy and reproducibility of values measured by the Respiradyne hand-held pulmonary function monitor to determine its suitability for bedside evaluation of patient response to bronchodilators. Methods: In the first phase of the investigation, we injected 14 artificial breaths with a 3.01-L super syringe to compare measured and known volumes (FVC). In the second phase, we used a sine-wave flow generator to compare volume (FVC) and flow measurements (FEV 1 , PEFR, FEF 25-75% ) of Respiradyne monitors to those of a laboratory-grade pneumotachometer. Ten measurements were observed on each of three monitors and the pneumotachometer at two different volume and flow settings to allow quantification of the variability in response between the two devices. In the third phase of the investigation, 26 healthy volunteers performed six FVC maneuvers, alternating between a Respiradyne monitor and a pneumotachometer. Results: We obtained a volume (mean ± SD) of 2.61 ± 0.24 L using the 3.01-L super syringe. There were statistically significant differences between the Respiradyne monitor and the pneumotachometer for all measurements at two volume and flow settings when a sine-wave flow generator was used. Additionally, variation among the three Respiradyne units was statistically significant for all measurements (FVC, FEV 1 , PEFR, FEF 25-75% ). There were statistically significant differences, in the flows and volumes generated by the volunteer group as measured by the Respiradyne monitor and the pneumotachometer, for all values except FEF 25-75% . However, variances between measurements on any given monitor were minimal. Conclusions: Although there were statistically significant differences among the Respiradyne monitors and the pneumotachometer, we do not consider those differences to be clinically important. The Respiradyne monitor appears to be reliable enough for use in bedside evaluation of spirometric response to bronchodilators.