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Abstract
BACKGROUND: The 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.
METHODS: This 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.
RESULTS: Compared with subjects with mild CFIP, subjects with severe CFIP had significantly larger ΔSpO2 and longer SpO2reduction 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.
CONCLUSIONS: Dynamic 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.
- 6-min walk test
- chronic fibrosing interstitial pneumonia
- oxygen saturation
- heart rate
- pulmonary functions
- mortality
- acute exacerbation
Footnotes
- Correspondence: Takeshi Inagaki PT PhD, Division of Rehabilitation, Chiba University Hospital, 1–8-1 Inohana Chuo-ku, Chiba 260–8677, Japan. E-mail: inagaki-tb{at}hospital.chiba-u.jp
Drs Terada and Tatsumi received a grant from the Respiratory Failure Research Group of the Ministry of Health, Labor and Welfare of Japan. Dr Inagaki received Grants-in-Aid for Scientific Research from the Ministry of Education, Culture, Sports, Science and Technology, Japan (25461148 and 25462158). The sponsors had no role in the design of the study, collection, and analysis of the data or preparation of the manuscript.
Dr Nagashima reports relationships with Pfizer R&D Japan, Fujimoto Pharmaceutical Corporation, SENJU Pharmaceutical, and Toray Industries. The other authors have disclosed no conflicts of interest.
- Copyright © 2023 by Daedalus Enterprises
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