Longitudinal changes in the nature, severity and frequency of COPD exacerbations.

Exacerbations are an important feature and outcome measure in chronic obstructive pulmonary disease (COPD), but little is known about changes in their severity, recovery, symptom composition or frequency over time. In this study 132 patients (91 male; median age 68.4 yrs and median forced expiratory volume in one second (FEV1) 38.4% predicted) recorded daily symptoms and morning peak expiratory flow. Patients were monitored for a median of 918 days and 1,111 exacerbations were identified. Patients with severe COPD (Global Initiative for Chronic Obstructive Lung Disease (GOLD) category III, n=38) had an annual exacerbation frequency of 3.43 x yr(-1), 0.75 x yr(-1) higher than those with moderate COPD (GOLD II, n=94). Exacerbation frequency did not change significantly during the study. At exacerbation onset, symptom count increased to 2.23, relative to a baseline of 0.36 set 8-14 days previously, and this increase rose by 0.05 x yr(-1). Recovery to baseline levels in symptoms and FEV1 took longer (0.32 and 0.55 days x yr(-1)). Sputum purulence at exacerbation became more prevalent over time by 4.1% x yr(-1) from an initial value of 17%. The results of this study suggest that over time, individual patients have more symptoms during exacerbations, with an increased chance of sputum purulence and longer recovery times.