ORIGINAL ARTICLEare characterized by an increase in cough, sputum production, worsening dyspnoea, or sputum purulence 4 . Although respiratory infections are suspected to be the main factor for the exacerbations, other factors such as industrial pollutants, allergens, sedatives, congestive heart failure, and pulmonary embolism, have also been identified 4,5,6,7 . Despite the frequency and the consequences of the exacerbation of COPD (ECOPD), its underlying pathological mechanism remains poorly understood. Only a handful of studies have focused on the functional 8 ,

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