The results of the multivariate logistic regression analysis showed that age ≥ 60 years, comorbid COPD, PCT ≥ 2 ng/mL, CRP ≥ 100 mg/L, PaO2 < 60 mmHg, and PaCO2 ≥ 50 mmHg were independent risk factors for poor clinical efficacy of BAL in the treatment of severe pneumonia patients (all p < 0.05) (Table 4). Here, CRP is linked to chronic obstructive pulmonary disease.