Diagnostic use of the resistive device in COPD patients

INTRODUCTION: Chronic obstructive pulmonary disease (COPD) is diagnosed in later or very advanced stages. The aim of the study was to evaluate feasibility of low respiratory resistive load (LRRL) in patients with COPD for a new objective method of early COPD diagnostics and to examine changes in pulmonary gas exchange during LRRL. METHODS: The study involved eleven patients with mild or moderate COPD and fourteen healthy adult volunteers. After anthropometric and spirometric measuring, pulmonary gas exchange was measured for 7 minutes using the breath-by-breath method under two conditions: 1) without respiratory resistive load (WRL); 2) with LRRL 0.4 cm H₂O · l^-1 · s. Valve system (Intersurgical, UK) was used as a resistive device. RESULTS: Decrease in oxygen consumption (VO₂) and carbon dioxide production (VCO₂) during LRRL was significantly greater in COPD patients than in healthy subjects (14 vs. 8 %, p<;0.009 and 16 vs. 10 %, p<;0.020 respectively). In contrast, tidal volume increased by 13 % in healthy subjects only. CONCLUSION: Pulmonary gas exchange shift during low respiratory resistive load appears to be a feasible criterion of early COPD diagnostics. Future research is needed to examine sensitivity and specificity of the method.