Inflammatory cell counts prior to and during exacerbation. Differential neutrophil, eosinophil, lymphocyte and macrophage counts were carried out on samples from COPD patients and corrected for weight of sputum. Samples were taken from patients prior to and during exacerbation (n = 12). Median cell counts are marked as diamonds. Data were analysed by a non parametric Wilcoxon signed rank test.