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

Background: May patients with interstitial lung disease (ILD) require supplementary oxygen (O) therapy to maintain normoxia. However, ambulatory O 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 O at baseline. Each subject completed two six-minute walk tests (6MWTs); for O users, one walk was completed while wearing a backpack (weight 7.2 pounds) containing a tank with compressed O, 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, O users received oxygen via a stationary delivery system. For both walks, O 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 O-containing backpack resulted in decreased distance covered during the 6MWT, and increased dyspnea and perceived exertion among O users. While wearing the weighted backpack, O non-users had a significantly lower peripheral O saturation and distance-saturation product. Compared with carrying O in the backpack, receiving O 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 O versus receiving O 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 O, practitioners should alert patients to this effect and help patients decide on the best O delivery mode to meet their needs.