Prediction and types of dead-space fraction during exercise in male chronic obstructive pulmonary disease patients

Abstract

AbstractA high dead space (VD) to tidal volume (VT) ratio during peak exercise (VD/VTpeak) is a sensitive and consistent marker of gas exchange abnormalities; therefore, it is important in patients with chronic obstructive pulmonary disease (COPD). However, it is necessary to use invasive methods to obtain VD/VTpeak, as noninvasive methods, such as end-tidal PCO2(PETCO2peak) and PETCO2adjusted with Jones' equation (PJCO2peak) at peak exercise, have been reported to be inconsistent with arterial PCO2at peak exercise (PaCO2peak). Hence, this study aimed to generate prediction equations for VD/VTpeakusing statistical techniques, and to use PETCO2peakand PJCO2peakto calculate the corresponding VD/VTpeaks (i.e., VD/VTpeakETVD/VTpeakJ).A total of 46 male subjects diagnosed with COPD who underwent incremental cardiopulmonary exercise tests with PaCO2measured via arterial catheterization were enrolled. Demographic data, blood laboratory tests, functional daily activities, chest radiography, two-dimensional echocardiography, and lung function tests were assessed.In multivariate analysis, diffusing capacity, vital capacity, mean inspiratory tidal flow, heart rate, and oxygen pulse at peak exercise were selected with a predictive power of 0.74. There were no significant differences in the PCO2peakvalues and the corresponding VD/VTpeakvalues across the three types (both p = NS).In subjects with COPD, VD/VTpeakcan be estimated using statistical methods and the PETCO2peakand PJCO2peak. These methods may have similar predictive power and thus can be used in clinical practice.