title: Supplemental oxygen users with pulmonary fibrosis perceive greater dyspnea than oxygen non-users.
abstract: BACKGROUND
  Exertional dyspnea is a hallmark symptom of fibrosing interstitial lung disease (fILD), and oxygen (O2) desaturation is common among patients with fILD. Supplemental O2 is prescribed to maintain normoxia and alleviate dyspnea. We sought to better understand the associations between O2 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 O2 (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 SpO2, 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 SpO2 < 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 (SpO2 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.
  
  
  CONCLUSIONS
  Dyspnea is a complex perception, and in patients with fILD, O2 may lessen, but does not resolve, it. Further research is needed to clarify why fILD patients who use O2 perceive greater levels of dyspnea with activity than O2 non-users.
authors.affiliation: Department of Respiratory Medicine, Nanjing Drum Tower Hospital, the affiliated Nanjing University Medical School, 321 Zhongshan Road, Nanjing, Jiangsu 210008 China.
authors.forename: Mengshu
authors.initials: M
authors.lastname: Cao
authors.affiliation: Division of Pulmonary, Critical Care, Sleep and Behavioral Medicine, Department of Medicine, National Jewish Health, Denver, Colorado USA.
authors.forename: Frederick S
authors.initials: FS
authors.lastname: Wamboldt
authors.affiliation: Interstitial Lung Disease Program, Department of Medicine, National Jewish Health, 1400 Jackson Street, Denver, 80206 Colorado USA.
authors.forename: Kevin K
authors.initials: KK
authors.lastname: Brown
authors.affiliation: Department of Internal Medicine, Saint Joseph Hospital, 1375 E 19th Ave, Denver, 80218 Colorado USA.
authors.forename: Jonathon
authors.initials: J
authors.lastname: Hickman
authors.affiliation: Interstitial Lung Disease Program, Department of Medicine, National Jewish Health, 1400 Jackson Street, Denver, 80206 Colorado USA.
authors.forename: Amy L
authors.initials: AL
authors.lastname: Olson
authors.affiliation: Interstitial Lung Disease Program, Department of Medicine, National Jewish Health, 1400 Jackson Street, Denver, 80206 Colorado USA.
authors.forename: Joshua J
authors.initials: JJ
authors.lastname: Solomon
authors.affiliation: Interstitial Lung Disease Program, Department of Medicine, National Jewish Health, 1400 Jackson Street, Denver, 80206 Colorado USA.
authors.forename: Jeffrey J
authors.initials: JJ
authors.lastname: Swigris
keywords: 6-min walk test; Dyspnea; Interstitial lung disease; Pulmonary fibrosis; Supplemental oxygen