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.

Keywords: Ambulatory oxygen therapy; Interstitial lung disease; Portable oxygen.