• Soh Imamura, Takeshi Inagaki, Mitsuhiro Abe, Jiro Terada, Takeshi Kawasaki, Kengo Nagashima, Koichiro Tatsumi, and Takuji Suzuki.
• Department of Respirology, Graduate School of Medicine, Chiba University, Chiba, Japan; and Division of Rehabilitation, Tokyo Women's Medical University Yachiyo Medical Center, Chiba, Japan.
• Respir Care. 2023 Mar 1; 68 (3): 356365356-365.

BackgroundThe 6-min walk test (6MWT) is a common assessment of exercise-induced hypoxemia and exercise capacity used in patients with chronic fibrosing interstitial pneumonia (CFIP). However, whether the dynamic changes in SpO2 and heart rate during the 6MWT are associated with mortality in patients with CFIP has been undefined.MethodsThis retrospective study enrolled 63 subjects with mild to severe CFIP who underwent the 6MWT. Subjects with CFIP were divided into 2 groups according to disease severity: mild, diffusing capacity of the lungs for carbon monoxide percentage predicted (%DLCO) > 55% and %FVC > 75%; and severe, %DLCO ≤ 55% and/or %FVC ≤ 75%. This study aimed to evaluate dynamic changes in the 6MWT including 6-min walk distance, change in SpO2 (ΔSpO2 ), SpO2 reduction time, SpO2 recovery time, change in heart rate (Δ heart rate), heart rate acceleration time, slope of heart rate acceleration, heart rate recovery at 1 min of rest after the 6MWT (HR-recovery), and dyspnea on exertion that are reflected by static pulmonary function and are related to exacerbation of CFIP and mortality.ResultsCompared with subjects with mild CFIP, subjects with severe CFIP had significantly larger ΔSpO2 and longer SpO 2 reduction time and recovery time. The slope of heart rate, heart rate immediately after the 6MWT, and HR-recovery were lower in subjects with severe CFIP than in those with mild CFIP. In multiple regression analysis, percent vital capacity was significantly associated with SpO2 reduction time, and %DLCO was significantly associated with ΔSpO2 and SpO2 recovery time. Subjects with ΔSpO2 of > 10% and SpO2 recovery time of > 79 s had a significantly higher risk for exacerbation and mortality.ConclusionsDynamic changes in SpO2 and heart rate during the 6MWT were associated with risk for exacerbation and mortality in subjects with CFIP. Impaired dynamic response of SpO2 could reflect likelihood of exacerbation and increased mortality in CFIP.Copyright © 2023 by Daedalus Enterprises.

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