C39-22 Risk Factors for Six Minute Walk Test Desaturation in Patients With Interstitial Lung Disease

Abstract Rationale The six-minute walk test (6MWT) is used to measure exercise ability and supplemental oxygen needs in patients with interstitial lung disease (ILD). As this test is resource intensive both for patients and providers, we aimed to find easily identifiable risk factors that identify which patients desaturate on 6MWT at clinic visits. Methods Patients in the University of Chicago ILD Registry were included in this study. Demographic and clinical data was extracted from the medical record, and ILD diagnosis was determined via multidisciplinary guidelines. The primary outcome of this study was desaturation, defined as SpO2 less than 89% at the end of the 6MWT. Mixed effects logistic regression models were employed to identify associations between vital signs, demography, clinical features, and desaturation, adjusting for repeat observations within the same individual. Receiver operating characteristic curve (ROC) analysis was performed to determine the performance characteristics of a predictive model incorporating age, gender, ILD subtype, crackles on exam, blood pressure, heart rate (HR), and respiratory rate. Results 189 patients undergoing 718 6MWTs were included. In univariable analyses, age (OR 1.06, 95% CI 1.00-1.11), male gender (OR 3.44, 95% CI 1.12-10.5), idiopathic pulmonary fibrosis (IPF) diagnosis (OR 6.93, 95% CI 1.77-27.2), and crackles (OR 2.97, 95% CI 1.27-6.95) were significantly associated with desaturation. HR (OR 1.02 for every beat per minute (BPM) increase, 95% CI 1.00-1.05) and hemoglobin (OR 1.37, 95% CI 0.99-1.89) trended toward significance. In the multivariable model controlling for liters of O2 via nasal cannula, HR (OR 1.04 for every BPM increase (95% CI 1.00-1.09, p = 0.04)) and crackles (OR 6.81, 95% CI 1.35-34.3) were the only variables significantly associated with desaturation. When restricting analysis to patients not on baseline oxygen, age (OR 1.06, 95% CI 1.00-1.12) and IPF (OR 7.43, 95% CI 1.61-34.3) were significantly associated with desaturation on univariable analysis, and these associations persisted on multivariable analysis. The AUC for a model of predicted probabilities utilizing the multivariable mixed effects regression model to predict desaturation was 0.98 (Figure). Conclusion In this study, IPF diagnosis, age, male gender, auscultatory crackles, hemoglobin, and HR were all associated with desaturation on 6MWT. Identifying variables that are correlated with risk of desaturation can help clinicians decide what patients should perform the test. This work could inform a future scoring system to quickly identify which patients are at low risk of desaturation and thus do not need to complete the test, saving time and resources. This abstract is funded by: None