The impact of carrying supplemental oxygen on exercise capacity and dyspnea in patients with interstitial lung disease.

ABSTRACT

BACKGROUND: May patients with interstitial lung disease (ILD) require supplementary oxygen (O2) therapy to maintain normoxia. However, ambulatory O2 delivery devices are constraining and cumbersome. The physiologic and symptomatic impact of these devices on ILD patients is unknown. METHODS: We conducted a prospective study of 30 clinically stable ILD patients (with varying disease severity), half of whom used O2 at baseline. Each subject completed two six-minute walk tests (6MWTs); for O2 users, one walk was completed while wearing a backpack (weight 7.2 pounds) containing a tank with compressed O2, and for non-users, one walk was completed with a similarly-weighted backpack. For each subject, during the second walk, no backpack was worn; for the second walk, O2 users received oxygen via a stationary delivery system. For both walks, O2 non-users wore a portable metabolic system, which measured variables related to respiratory physiology and gas exchange. Borg dyspnea and exertion ratings were recorded after each walk. RESULTS: Wearing the O2-containing backpack resulted in decreased distance covered during the 6MWT, and increased dyspnea and perceived exertion among O2 users. While wearing the weighted backpack, O2 non-users had a significantly lower peripheral O2 saturation and distance-saturation product. Compared with carrying O2 in the backpack, receiving O2 via the stationary concentrator resulted in the largest improvement in walk distance for the three subjects with greatest impairment at baseline (6MWT ≤ 300 m). CONCLUSION: Among ILD patients, carrying portable O2 versus receiving O2 via a stationary concentrator results in significantly greater dyspnea and shorter distances covered in timed testing. Patients with the greatest impairment may be affected most. When prescribing O2, practitioners should alert patients to this effect and help patients decide on the best O2 delivery mode to meet their needs.