Substudy of Protocol 2019-002498-80 - NCT04223050: Comparing Mortality for Low vs High Peripheral Oxygen Saturation in COPD-patients With Acute Exacerbation (O2flow-COPD)

Studies have shown that oxidative stress plays a critical role in the pathogenesis of COPD and its comorbidities. Oxidative stress refers to a state in which the activity of oxidants (e.g. reactive oxygen species (ROS)) outweighs that of antioxidants. ROS can be introduced exogenously by for example cigarette smoke and atmospheric pollution, but is also produced endogenously as a byproduct of ATP production in mitochondria or from immune cells during oxidative burst. When high fractions of inspired oxygen are administered, excess O2 can lead to formation of additional ROS, which depletes antioxidants and induces an inflammation with leukocyte-derived inflammatory mediators migrating to the site of injury. In turn, this causes cellular hypertrophy, increased surfactant secretion, and cellular influx of monocytes and mast cells. During the final, fibrotic phase of oxygen toxicity, irreversible, persistent destruction of the pulmonary lining have occurred with collagen disposition, thickening of pulmonary interstitial space, and fibrosis. This substudy therefore aim to investigate the relation between oxygen therapy in COPD patients admitted with acute exacerbation, oxidative stress, and mortality.