A 60-year-old woman with chronic cough and dyspnea for 18 years, experiencing wheezing on exertion and lower extremity edema for 3 years. Over the past week, worsening cough and dyspnea with poor response to antibiotics and diuretics, accompanied by insomnia and irritability for 2 days. Blood gas analysis: pH 7.35, PaO₂ 56 mmHg, PaCO₂ 75 mmHg, AB 41 mmol/L, Cl⁻ 78 mmol/L. Based on the history, the most likely diagnosis is: