A Ramped Treadmill Protocol Exercise Test Identifies Higher Ambulatory Oxygen Needs in Idiopathic Pulmonary Fibrosis...

Rationale: In the United States, ambulatory oxygen is recommended for patients with idiopathic pulmonary fibrosis (IPF) and chronic obstructive pulmonary disease (COPD) who experience symptomatic exertional hypoxemia. Ambulatory oxygen need is often determined by submaximal hall walk testing; however, this may fail to accurately characterize exertional hypoxemia in some patients. Objectives: Assess for differences in ambulatory oxygen needs between patients with IPF and COPD who completed a ramped treadmill protocol exercise test (RTPET) and correlate oxygen flow rates determined at highest-level (HL) exertion with lung function and exercise parameters. Oxygen need is defined as the flow rate needed to maintain oxygen saturation ⩾90% in patients who desaturate to ⩽88%. Methods: We conducted a retrospective review of RTPET results for patients with IPF and COPD who also recently completed spirometry. The RTPET has three phases: rest, submaximal usual pace (UP) walking at 0% treadmill grade for 3 minutes, and HL walking at the UP walk speed with increasing treadmill grade by 2% every 2 minutes. Patients with IPF were part of a clinical registry, whereas patients with COPD were identified based on diagnosis coding and spirometry (forced expiratory volume in 1 s/forced vital capacity < 0.70). The RTPET for both groups was completed based on a pulmonologist's referral. Results: We included 329 patients with IPF and 2,343 patients with COPD. A greater proportion of patients with IPF required ambulatory oxygen to maintain saturation ⩾90% at HL exertion. After adjusting for demographic covariates and exercise parameters, patients with IPF required higher ambulatory oxygen flow rates than subjects with COPD with similar diffusion capacity of carbon monoxide values. Of patients who did not require oxygen with submaximal UP testing, 49% with IPF and 24% with COPD required oxygen at HL exertion. Conclusions: The RTPET identified higher oxygen flow needs at HL exertion in patients with IPF versus patients with COPD; however, in both diseases, there was a significant proportion of patients who were only found to have exertional desaturation at HL exertion. Reliance on submaximal testing may fail to meet the needs of patients with IPF and COPD. Further studies are needed to determine if oxygen prescriptions targeting the highest level of desaturation improve clinical outcomes, symptoms, or quality of life.