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Background: Supplemental oxygen is widely used for dyspnea relief; however, its efficacy is yet to be verified. This study aimed to determine the efficacy of supplemental oxygen for dyspnea relief in patients with advanced progressive illness., Methods: In this systematic review, several databases, including MEDLINE and EMBASE, were searched to identify eligible randomized controlled trials (RCTs) on the topic published up to September 23, 2019. The search criteria included RCTs investigating patients with advanced progressive illness (advanced cancer, chronic obstructive pulmonary disease, and chronic heart failure). The study protocol was registered with PROSPERO (No. CRD42020161838). Separate analyses were pre-planned regarding the presence or absence of resting hypoxemia., Results: RCTs investigating supplemental oxygen for dyspnea relief in participants with and without resting hypoxemia (39 and five, respectively) were included in the study. Heterogeneity of supplemental oxygen for dyspnea in RCTs, including participants without resting hypoxemia was evident; hence, post-hoc analyses in four subgroups (supplemental oxygen during exercise or daily activities, short-burst oxygen, continuous supplemental oxygen, and supplemental oxygen during rehabilitation intervention) were conducted. In the meta-analysis, supplemental oxygen during exercise was found to improve dyspnea in patients without resting hypoxemia compared with that in the control (standardized mean difference = -0.57, 95% confidence interval = -0.77 to -0.38). However, supplemental oxygen for the other subgroups failed to improve patients' dyspnea., Conclusion: The results of this systematic review do not support supplemental oxygen therapy for dyspnea relief in patients with advanced progressive illness, except during exercise., Competing Interests: Conflict of Interest Takeo Nakayama has stock ownership or options from Bon Inc. and has received lecture fees from Pfizer Japan Inc., Janssen Pharmaceutical K·K., and Eli Lilly Japan K.K. He has also received funding from I&H Co., Ltd., Cocokarafine Group Co., Ltd., and Konica Minolta, Inc. and subsidies or donations from CancerScan and YUYAMA CO., LTD. The other authors have no conflict of interest., (Copyright © 2023 [The Author/The Authors]. Published by Elsevier B.V. All rights reserved.)

The α,β-unsaturated aldehyde 4-hydroxy-2-nonenal (4-HNE) is an endogenous product of oxidative stress that is found at increased levels in the lungs of patients with chronic obstructive pulmonary disease (COPD) and animal models of this lung disorder. In the present study, levels of 4-HNE adducts were increased in two different mouse models of COPD. Challenging lungs with 4-HNE enlarged the airspace and induced goblet cell metaplasia of the airways in mice, two characteristics of COPD. 4-HNE induced the accumulation of inflammatory cells expressing high levels of MMP-2 and MMP-9. Our results indicate that 4-HNE production during oxidative stress is a key pathway in the pathogenesis of COPD., (Copyright © 2012 Elsevier Inc. All rights reserved.)