Supplemental oxygen users with pulmonary fibrosis perceive greater dyspnea than oxygen non-users

BACKGROUND: Exertional dyspnea is a hallmark symptom of fibrosing interstitial lung disease (fILD), and oxygen (O(2)) desaturation is common among patients with fILD. Supplemental O(2) is prescribed to maintain normoxia and alleviate dyspnea. We sought to better understand the associations between O(2) and dyspnea in fILD during the 6-min walk test (6MWT). METHODS: 1326 fILD patients compose the sample group. Borg dyspnea and other 6MWT variables were compared between subjects who performed the test without (non-users) versus with O(2) (users). RESULTS: There were 812 users and 514 non-users; users were older, more likely to have smoked, had greater body mass index, and had more severe fILD. Despite a similar 6-min SpO(2), users perceived greater dyspnea than non-users (Borg 3.9 ± 2.0 vs 2.9 ± 1.7, p < 0.0001). Whether subjects became hypoxemic (6-min SpO(2) < 89 %) or not during the walk, the results were the same: users perceived greater dyspnea than non-users (hypoxemic: users 3.5 ± 2.1 vs non-users 2.7 ± 1.8, p < 0.0001; non-hypoxemic: users 3.4 ± 1.9 vs non-users 2.4 ± 1.6, p < 0.0001). Among subjects who did not desaturate (SpO(2) drop < 4 %), users walked a shorter distance (944.9 ± 367.0 vs 1385.3 ± 322.4 feet, p < 0.0001) but perceived greater dyspnea than non-users (3.3 ± 1.6 vs 2.3 ± 1.7, p = 0.005). No combination of potentially influential predictor variables entered in multivariate models explained more than 11 % of the variance in dyspnea ratings. CONCLUSION: Dyspnea is a complex perception, and in patients with fILD, O(2) may lessen, but does not resolve, it. Further research is needed to clarify why fILD patients who use O(2) perceive greater levels of dyspnea with activity than O(2) non-users.