Association of Recovery Rate From Exertional Desaturation With Disease Progression and Mortality Risk in Patients...

Patients with fibrotic interstitial lung disease (fILD) often develop progressive disease with accelerated lung function decline, as well as increased mortality risk. Exertional desaturation during a 6-minute walk test (6MWT) is associated with adverse outcomes in fILD; however, limited data inform the impact of recovery time from exertional oxygen (O₂) desaturation, independent of hypoxemia.

Is recovery time from exertional desaturation following 6MWT associated with disease severity and progression in patents with fILD?

This multicenter prospective cohort study included adult patients with fILD who underwent 6MWT at the University of Calgary or University of Chicago ILD clinics. Recovery index (RI) was calculated incorporating degree of O₂ desaturation, rate of recovery within 3% of baseline O₂ saturation, and supplemental O₂ use, with higher RI indicating prolonged recovery. The relationship between RI and baseline lung function was assessed by using generalized linear models. Impact on disease progression (composite of death, lung transplantation, or ≥ 10% FVC decline) was assessed by using Cox regression analysis. RI was evaluated in combination with the interstitial lung disease/gender, age, physiology (ILD-GAP) score as a novel mortality risk prediction tool.

Among 194 patients who completed a 6MWT (Calgary, n = 94; Chicago, n = 100), a higher RI was associated with lower baseline lung function and higher ILD-GAP score. Elevated RI was also associated with disease progression in the overall cohort, driven by the Chicago cohort (HR, 3.14; 95% CI, 1.50-6.62; P = .001). Combining RI with GAP-ILD score improved mortality risk prediction compared with the ILD-GAP score alone (ILD-GAP C-index, 0.57; ILD-GAP + RI C index, 0.60).

Our results show that RI is a novel measure of recovery from exertional desaturation post-6MWT, which is associated with baseline lung function and disease progression in patients with fILD, independent of exertional hypoxemia. In this analysis, adding RI to the ILD-GAP score improved mortality risk prediction. External replication studies are needed to validate the clinical and prognostic utility of the RI.