Abstract
Introduction: Spirometry is the gold standard in diagnosing COPD and asthma. However, the success of a measurement is highly dependent on patient cooperation and the experience of the technician. Therefore it is desirable to utilize an additional measurement technique at reasonable costs, which is completely independent on patient cooperation. Pilot studies have indicated that the shape of the volumetric capnogram (capnovolumetry) is modified by airway obstruction and might allow to diagnose an obstruction and ventilation inhomogeneity.
Methods: 95 subjects were analyzed in a prospective cohort study. An ultrasound based spirometer was used, which was also capable of measuring capnovolumetry. Several parameter of the volumetric capnogram have been analyzed. Reference values for specific parameters were determined using a ROC curve in order to calculate sensitivity and specificity.
Results: Significant differences (p<0.01) between the different groups were found for the slope of the alveolar plateau (SIII) and the angle between the ascending phase (SII) and the alveolar plateau. Those parameters showed a strong correlation to FEV1 (SIII, r=0.744) and RAW (SIII, r=0.517). In order to distinguish between healthy subjects and COPD patients, SIII as a parameter showed a sensitivity of 90% and specificity of 86%.
Conclusions: It has been proved that capnovolumetry is quantitative method for analyzing the presence and the severeness of a COPD. Considering the advantages of this method, in particular the effort independency and the measurement during tidal breathing, capnovolumetry opens new possibilities in the monitoring of respiratory diseases, especially for children, bedside diagnostics and at home.
- Copyright ©the authors 2016
