Role of single-breath diffusing capacity for carbon monoxide in patients with chronic obstructive pulmonary disease

Background Chronic obstructive pulmonary disease (COPD) is a common, preventable, and treatable disease characterized by persistent respiratory symptoms and airflow limitation that is due to airway and/or alveolar abnormalities, usually caused by significant exposure to noxious particles or gases. The chronic airflow limitation that characterizes COPD is caused by a mixture of small airway disease (e.g. obstructive bronchiolitis) and parenchymal destruction (emphysema), the relative contributions of which vary from person to person. Aim The aim of the study was to measure diffusing capacity for carbon monoxide using single-breath technique in different stages of COPD. Patients and methods A total of 100 patients with COPD with mild to very severe obstruction were included in the study. Results There was a statistically significant negative (inverse) correlation between both transfer capacity of the lung (TLCO%) and KCO and PCO2 and HCO3, and there was a statistically significant positive (direct) correlation between both TLCO% and KCO and PO2, and arterial oxygen saturation. There was a statistically significant positive (direct) correlation between forced vital capacity %, forced expiratory volume in 1 s%, forced expiratory flow (FEF)25%, FEF50%, and FEF75% and each of TLCO% and KCO. Conclusion Decline in forced expiratory volume in 1 s/forced vital capacity is associated with decline in diffusing capacity of the lung for carbon monoxide, and it is affected more in patients with severe and very severe degrees of chronic obstructive pulmonary disease (COPD).