The aim of the study is to assess the role of NAC in the treatment of acute COPD exacerbation in terms of clinical, physiological, and laboratory parameters, including PaO2, PaO2/FiO2 ratio, PaCO2, SaO2, end tidal CO2, length of stay, coughing, wheezing, dyspnoea, need for supplemental oxygen sputum volume, FEV1, and blood inflammatory markers.