Objectives: To determine lung functional parameters of 117 patients with stable chronic obstructive pulmonary disease (COPD) at 103 Hospital from October, 2013 to March, 2016 by plethysmography and to study the relationship among these parameters with stages of stable COPD. Methods: A prospective and cross-descriptive study. | Journal of military pharmaco-medicine no7-2017 RESULTS OF LUNG FUNCTIONAL PARAMETERS MEASURED BY PLETHYSMOGRAPHY IN STABLE COPD Pham Thi Phuong Nam*; Dong Khac Hung*; Nguyen Huy Luc*** Summary Objectives: To determine lung functional parameters of 117 patients with stable chronic obstructive pulmonary disease (COPD) at 103 Hospital from October, 2013 to March, 2016 by plethysmography and to study the relationship among these parameters with stages of stable COPD. Methods: A prospective and cross-descriptive study. Results: A decrease in the pulmonary ventilatory indices, difusing capacity for carbon monoxide (DLCO) and the increase in airway resistance, distention pulmonary indices in patients with stable COPD were recorded. In addition to FEV1 (forced expiratory volume) parameter, MVV (maximal voluntary ventilation), RV/TLC (residual volume/total lung capacity), raw (resistance air way), DLCO (diffusing capacity for carbon monoxide) parameters highly related with the severity of the disease (eta = ; eta = ; eta = , eta = ), respectively with p < . Conclusions: There were variations of lung functional parameters and these variations related with the classification of the severity of COPD. MVV, raw, RV/TLC are very important parameters in prognosis the severity of COPD. * Keywords: Lung functional parameters; Chronic obstructive pulmonary disease; Plethysmography; Stable COPD. INTRODUCTION Chronic obstructive pulmonary disease (COPD) is a respiratory disease with an increase in morbidity and mortality. In 2012, there were about 3 million deaths due to COPD, accounting for nearly 6% of the causes of death. Particularly, in Vietnam, the incidence of disease is quite high (), which is the top of 12 countries in Southeast Asia [11]. Pulmonary ventilation, static lung, resistance airway, diffusion of alveoli - capillaries explorations are very valuable in the complete evaluation of COPD, one of the three major components to evaluate the .