No room to breathe: the importance of lung hyperinflation in COPD

Patients with chronic obstructive pulmonary disease (COPD) are progressively limited in their ability to undertake normal everyday activities by a combination of exertional dyspnoea and peripheral muscle weakness. COPD is characterised by expiratory flow limitation, resulting in air trapping and lung hyperinflation. Hyperinflation increases acutely under conditions such as exercise or exacerbations, with an accompanying sharp increase in the intensity of dyspnoea to distressing and intolerable levels. Air trapping, causing increased lung hyperinflation, can be present even in milder COPD during everyday activities. The resulting activity-related dyspnoea leads to a vicious spiral of activity avoidance, physical deconditioning, and reduced quality of life, and has implications for the early development of comorbidities such as cardiovascular disease. Various strategies exist to reduce hyperinflation, notably long-acting bronchodilator treatment (via reduction in flow limitation and improved lung emptying) and an exercise programme (via decreased respiratory rate, reducing ventilatory demand), or their combination. Optimal bronchodilation can reduce exertional dyspnoea and increase a patient's ability to exercise, and improves the chance of successful outcome of a pulmonary rehabilitation programme. There should be a lower threshold for initiating treatments appropriate to the stage of the disease, such as long-acting bronchodilators and an exercise programme for patients with mild-to-moderate disease who experience persistent dyspnoea.