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 SpO2 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. SpO2 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 SpO2 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.