First fully clinically oriented report in body plethysmography utilizing resistance-volume charts

Introduction: According to established recommendations, the clinical interpretation of body plethysmography examinations is usually based on airways resistance (Raw) and static lung volumes (RV, FRCpleth, TLC). Current body plethysmography graphics displayed on the PFT report use body loops and shutter curves. These are still on the level of Du Bois’s standards in which they have a clear technical orientation. However the crucial relationship between airways resistance and lung volumes is neither presented in a simple form nor shown in comparison to their predicted values. Additional evaluation of parameter and reference tables is required. Methods: An alternative body plethysmography report allows the generation and presentation of the instantaneous relationship between airways resistance and lung volume over the entire breathing cycle. This is achieved by a dedicated resistance-volume (R-V) transformation. The time courses of the primary signals of flow, volume, plethysmography shift volume and occlusion pressure are processed simultaneously and then linked to corresponding absolute lung volumes. Results: All conventional clinical parameters of body plethysmography are presented in one R-V chart. The R-V graph displays the within-breath course of airways resistance dependent upon absolute lung volume. Predicted and abnormal areas of Raw and FRCpleth and the variation of Raw complete this graphic. Conclusion: Plotting airways resistance during quiet tidal breathing and linking to absolute lung volumes is visually diagnostic to changes in chest mechanics and can aid in the interpretation of plethysmography test results above conventional graphics.