Hypoxaemia enhanced peripheral muscle oxidative stress in COPD

Chronic bronchitis and pulmonary emphysema, also know as chronic obstructive pulmonary disease (COPD), is the only leading cause of death with a rising prevalence.¹ Typically, the reduced lung function of COPD patients is associated with a general deconditioning of muscle function and the consequent development of a sedentary lifestyle.² There is clear evidence that pulmonary rehabilitation programmes that involve generic physical exercise training can improve exercise capacity and state of health in patients with COPD,³ so outpatient and home based exercise training are part of the rehabilitation programme for these subjects in Western countries.⁴

The role of co-factors such as hypoxia and inflammation on the health of COPD patients and the resulting improvements of exercise performance with training are poorly understood, but the paper by Koechlin and colleagues⁵ in this issue of Thorax shows that exercise performance and peripheral muscle defects in patients with COPD relate to the level of arterial oxygenation. Using biochemical measures, the authors found that COPD patients with hypoxaemia had higher basal and resistance exercise induced levels of oxidatively damaged lipids and proteins in the vastus lateralis muscle than non-hypoxaemic patients. At baseline, the muscles of hypoxaemic COPD patients also had more lipofuscin inclusions in the muscle fibres and higher neutrophil numbers in the quadriceps muscle. These results suggest that adequate muscle oxygenation is critical to preventing the accumulation of wasteful oxidised lipid products and the harmful downstream reactions that are potentially associated with muscle wasting.^6–8 Correlation analysis of endurance and arterial oxygen …