TOPLINE:

Recovery from exertional desaturation after a 6-minute walk test (6MWT), measured using a recovery index (RI), was associated with poorer baseline lung function and a higher risk for disease progression in patients with fibrotic interstitial lung disease.

METHODOLOGY:

• This prospective cohort study evaluated whether recovery from exertional desaturation after a 6MWT was associated with disease severity and progression in 194 adults with fibrotic interstitial lung disease in Calgary (n = 94; 51.1% male) and Chicago (n = 100; 28.0% male).
• Recovery after the 6MWT was quantified using an RI, a novel tool that combines the degree of desaturation, time to recover to within 3% of baseline peripheral oxygen saturation, and need for supplemental oxygen; higher RI values indicated prolonged recovery. Exertional desaturation was defined as a drop of more than 3% from baseline peripheral oxygen saturation at the end of the 6MWT.
• Baseline 6MWT measurements were retrieved from the electronic medical records, and lung function data were obtained from the pulmonary function test closest to and within 3 months of the baseline 6MWT.
• The primary outcome was a composite endpoint of death, lung transplantation, or a decline of 10% or more in the absolute forced vital capacity within 12 months. Secondary outcomes included lung transplant-free survival.
• The median follow-up duration was 20.0 months for Calgary patients and 30.1 months for Chicago patients.

TAKEAWAY:

• The median RI was 2.62 for Calgary patients and 3.61 for Chicago patients. Among those who experienced desaturation, the median RI was 7.69 and 7.35 for Calgary and Chicago patients, respectively.
• An RI higher than 3.97 was associated with an increased risk for the composite outcome in the combined (hazard ratio [HR], 2.06; P = .007) and Chicago (HR, 3.14; P = .001) cohorts in unadjusted analyses; similar associations were observed for lung transplant-free survival in these two cohorts.
• A higher RI was significantly associated with a lower percent predicted forced vital capacity at baseline and higher interstitial lung disease gender, age, physiology scores in adjusted analyses in both cohorts (P < .05 for all).
• Adding RI to the interstitial lung disease gender, age, physiology score slightly improved prediction of lung transplant-free survival compared with using the score alone, but the improvement was not statistically significant.

IN PRACTICE:

“The RI represents a potential new prognostic tool, which can be used for patients completing 6MWT with or without supplemental O₂ and regardless of fILD [fibrotic interstitial lung disease] subtype. It is associated with disease severity and may be useful in predicting TFS [transplant-free survival] and disease progression in clinical practice or research settings,” the authors of the study wrote.

SOURCE:

The study was led by Albina Tyker, MD, McMaster University, Hamilton, Ontario, Canada. It was published online on December 30, 2025, in Chest.

LIMITATIONS:

The Calgary and Chicago cohorts differed at baseline, notably in lung function. Calgary’s higher altitude may have worsened exertional oxygen desaturation. Relying on end-of-6MWT peripheral oxygen saturation rather than the nadir value may have missed patients with more pronounced desaturation.

DISCLOSURES:

No financial support was received for the study. Some authors disclosed receiving grants, honoraria, consulting fees, and support for travel to meetings; serving on the data and safety monitoring board and adjudication committee; and having other relationships with various organizations and pharmaceutical companies.

This article was created using several editorial tools, including AI, as part of the process. Human editors reviewed this content before publication.