In summary, age ≥ 60 years, comorbid COPD, PCT ≥ 2 ng/mL, CRP ≥ 100 mg/L, PaO2 < 60 mmHg, and PaCO2 ≥ 50 mmHg are independent risk factors affecting the clinical efficacy of BAL treatment. Here, CRP is linked to chronic obstructive pulmonary disease.