EVALUATION OF VENTILATION-PERFUSION RATIO IN CHRONIC OBSTRUCTIVE PULMONARY DISEASE

Abstract

Objective: To study ventilation-perfusion ratio (VPR) in patients with chronic obstructive pulmonary disease (COPD) using method of volumetric capnography. Methods: 35 patients with COPD II-IV stages and 17 volunteers without pathology of the respiratory system (control group) were examined. Using SpiroScout (Ganshorn, Germany) with built-in function of volumetric capnography, spirography and volumetric capnography were implemented. Symptoms in patients with COPD were evaluated using mMRC and CAT. Results: Statistically significant differences between the patients with COPD and the control group were identified in a number of parameters of volumetric capnography characterizing VPR. VDBohr, VDalv and their ratio to VT in patients with COPD were higher than in individuals of the control group (VDBohr – 361 [299-486] and 280 [215-463] ml, p=0.042; VDBohr/VT – 0.43 [0.40-0.51] and 0.35 [0.31-0.44], p=0.001; VDalv – 211 [142-290] and 81 [49.5-244.5] ml, p=0.012; VDalv/VT – 0.24 [0.20-0.34] and 0.13 [0.08-0.23], p=0.001). The slope of the 2nd phase of the capnogram in COPD was more smooth (dMM/dV2 – 2.0 [1.7-2.7] and 2.5 [2.2-3.2] g/mol×l, respectively; p=0.013), and the slope of the 3rd phase was steeper than in the individuals without pathology of the respiratory system (dMM/dV3 – 0.38 [0.29-0.51] and 0.22 [0.13-0.34] g/mol×l, respectively; p<0.001). Angle α in the group with COPD was increased in comparison with the control group (136 Conclusion: The conducted study identified derangement of VPR in patients with COPD. Volumetric capnography is an easy-to-use technique that allows evaluating VPR.

Keywords

• ventilation-perfusion ratio
• dead space
• chronic obstructive pulmonary disease
• volumetric capnography.