Objective: We investigated ventilation inhomogeneity indices (Sacin, Scond) in patients with chronic obstructive pulmonary disease (COPD) using the multiple breath nitrogen washout test (MBNW) and determined the correlation between the 2 indices ( Scond and Sacin, as a measure of ventilation inhomogeneity in conductive and acinar zones of the lungs, respectively) and lung function to investigate the significance of assessing the COPD severity with ventilation inhomogeneity indices.
Methods: Forty-three stable COPD patients and 56 non-smoking healthy subjects were recruited from November 2014 to February 2015. The differences of ventilation inhomogeneity indices (Sacin, Scond) between the 2 groups were compared, and the correlation between ventilation inhomogeneity indices and traditional parameters of lung function were determined using Pearson linear correlation. According to the FEV1%pred=50%, COPD patients were divided into 2 groups and ventilation inhomogeneity indices (Sacin, Scond) were compared between groups.
Results: Compared with the healthy control group,Sacin [0.320 (0.238, 0.432) vs 0.097 (0.073, 0.144), u=144.5, P<0.001], and Scond [0.082 (0.043, 0.103) vs 0.018 (0.007, 0.028), u=103.5, P<0.001] in COPD patients were significantly increased, and the difference was statistically significant. Sacin and Scond were negatively correlated with FVC%pred (r=-0.686, -0.551, both P<0.001), FEV1%pred (r=-0.681, -0.475, both P<0.01), FEV1/FVC (r=-0.458, -0.210, both P<0.01). Sacin was negatively correlated with DLCO (r=0.413, P<0.01). With the increase in the severity of the disease, Sacin and Scond increased gradually.
Conclusion: Sacin and Scond in COPD patients increased significantly, which was significantly correlated with lung function. COPD has ventilation inhomogeneity in conductive and acinar zones and ventilation inhomogeneity indices can be used to evaluate the severity of COPD.