Pulmonary Function Test in Chronic Obstructive Pulmonary Disease Related to Diffusion Lung Capacity for Carbon Monoxide and Six-minute Walk Test at Tertiary Care Center

A BSTRACT Introduction: Chronic obstructive pulmonary disease (COPD) is a progressive respiratory condition characterized by airflow limitation. Spirometry forms the cornerstone of diagnosis. Additional parameters, such as diffusing capacity for carbon monoxide (DLCO) and 6-min walk test (6MWT), can offer deeper insights into disease severity and prognosis. This study aimed to evaluate the clinical, radiological, and functional profiles of COPD patients and explore correlations. Materials and Methods: This prospective observational study included 201 patients diagnosed with COPD at a tertiary care center. Detailed clinical, spirometry, DLCO, 6MWT, arterial blood gas (ABG), chest X-ray, and computed tomography of the thorax were performed. Statistical analysis was conducted using Spearman’s correlation between DLCO, Global Initiative for Chronic Obstructive Lung Disease (GOLD) stage, and 6MWT. Results: The mean age was 56.73 ± 12.93 years, with a male predominance (65%). Past tuberculosis (53.73%) and smoking (39.8%) were the leading etiologies. Most patients were in GOLD stage 3 (44%) and CAG Class E (54%). ABG analysis was normal in 78.11% of cases, while 47% of cases had pulmonary hypertension. DLCO was severely reduced (<40%) in 97.39% of tested patients, and 62.69% of cases showed significant desaturation (≥4%) on 6MWT, with 72.14% covering 150–249 m. Chest imaging showed hyperinflation, fibrosis, and bronchiectasis. A significant negative correlation was found between DLCO and GOLD stage (ρ = −0.3169, P < 0.001) and a positive correlation between DLCO and 6MWT distance (ρ = 0.4153, P < 0.001). Conclusion: DLCO’s significant association with GOLD stage and 6MWT highlights its potential in routine COPD evaluation. Incorporating DLCO into clinical practice may enhance patient stratification, guide therapy, and improve prognostication.