Extrathoracic muscle wasting in exacerbations of COPD: No longer outside the region of interest

While airflow limitation is used to diagnose chronic obstructive pulmonary disease (COPD), it is well established that forced expiratory volume in one second alone relates poorly to mortality1 or health-related quality of life.2 Skeletal muscle dysfunction has been shown to be a better predictor than lung function for both prognosis3 and risk of hospitalisation.4 Moreover, skeletal muscle weakness is increasingly recognised as an important component of both frailty and sarcopaenia. Acute exacerbations of COPD (AECOPD) are a feature of many patients with COPD, with intermittent worsening of symptoms contrasting to many other chronic conditions. The impact of exacerbations is well established, with prevention and treatment an important goal for therapy with COPD. [Opening paragraph]