Fujimoto Y, et al. - This study investigated the relationships between desaturation–distance ratio (DDR) and emphysema and pulmonary hypertension (PH). It is concluded that DDR is a good index of emphysema and PH in COPD patients. The findings suggested that the six-minute walk test (6MWT) is widely used to evaluate COPD, and DDR could help with the early diagnosis of COPD.

Methods

• For the purpose of this study, the researchers gathered the following data for seventy-four stable COPD outpatients: lung function tests (%FEV_1.0 and %DLCO), 6MWT distance and desaturation, and area of emphysema on computed tomography (percentage of low attenuation area).
• Enlargement of the pulmonary artery (PA) was evaluated by the ratio of the diameter of the PA to that of the aorta (PA:A ratio) as an index of PH.
• DDR was computed by the distance traveled and the degree of desaturation reached during a 6MWT.
• The connections between study outcomes were evaluated with Spearman’s rank-correlation analysis.
• Receiver operating characteristic (ROC) curves were utilized to determine the threshold values with the optimum cutoff points for predicting severe or very severe airway obstruction, pulmonary diffusing capacity disorder, moderate or severe emphysema, and enlargement of the PA.

Results

• The study results showed that DDR correlated significantly with %FEV_1.0, %DLCO, %LAA, and PA:A ratio.
• It was found that DDR demonstrated high accuracy (area under the ROC curve >0.7) for predicting severe or very severe airway obstruction, pulmonary diffusing capacity disorder, moderate or severe emphysema, and enlargement of the PA.