Classification of Patients Based on Dyspnea and Desaturation During Exercise in Interstitial Lung Disease

Background: Dyspnea and desaturation during exercise are essential assessment items for pulmonary rehabilitation. Characterizing patients using these 2 factors may be important for providing more effective pulmonary rehabilitation. This study aimed to categorize subjects with interstitial lung disease (ILD) using dyspnea and desaturation at the end of the 6-min walk test (6MWT). Methods: This was a retrospective study including 230 stable subjects with ILD who underwent 6MWT in our out-patient department at a general hospital in Japan. The modified Borg scale and oxygen saturation determined by S_pO2 at the end of the 6MWT were used for cluster analysis using the k-means method with k = 4. Results: Subjects were classified into 4 characteristic clusters. S_pO2 at the end of the 6MWT was lower in cluster 4 (80.5 ± 3.0%) than in clusters 1 (94.3 ± 2.0%), 2 (94.3 ± 1.9%), and 3 (87.9 ± 1.8%) and was lower in cluster 3 than in clusters 1 and 2. The modified Borg scale score at the end of the 6MWT was higher in clusters 2 (4 [3-8]), 3 (3 [0-9]), and 4 (4 [0-7]) than in cluster 1 (0.5 [0-2.0]) and was higher in cluster 2 than in cluster 3. Conclusions: Subjects with ILD were classified into 4 characteristic clusters using dyspnea and S_pO2 at the end of the 6MWT. The 4 clusters are characterized as follows: Cluster 1 had mild desaturation and mild dyspnea; cluster 2 had mild desaturation and severe dyspnea; cluster 3 had both moderate desaturation and dyspnea, and cluster 4 had both severe desaturation and dyspnea. These classification data offer insight for individualized pulmonary rehabilitation for patients with ILD.