Distribution of the main variables related to the patient's COPD prior to the exacerbation and to the severity of the acute COPD process upon arrival in the EDs.

Classes have been labeled in alphabetical order. Each cell shows the number and percentage (calculated over the non missing values) of patients with each condition (row) for categorical variables and mean and 95% confidence interval for continuous variables.*Statistically significant differences between groups in continuous variables are shown with superscripts represented by the code of the group (A, B, C and D).†It refers to previous hospitalizations for ECOPD in the previous year.Abbreviations used in the text: emergency department (ED); Charlson comorbidity index (CCI); previous treatment with continuous positive airway pressure (CPAP), invasive mechanical ventilation (IMV); oxygen therapy (OT); forced expiratory volume in one second (FEV1%) and confidence interval (CI).