Bronchoalveolar Lavage Fluid Analysis in Severe COVID-19: Insights Into Cellular and Microbiological Characteristics.

Introduction: This study aimed to describe bronchoalveolar lavage fluid (BALF) findings in cases of refractory respiratory failure, despite standard treatment, among patients with severe coronavirus disease 2019 (COVID-19), compare BALF findings between patients with mechanical ventilation (MV) weaning success and those with failure within 28 days, and evaluate the safety and impact on respiratory mechanics of BALF examination in patients with severe COVID-19. Methods: This study was conducted at the Department of Emergency Medicine, Sapporo Medical University, Japan. We included 21 patients with concurrent severe COVID-19 and refractory respiratory failure who could not be weaned from MV despite standard treatment. We compared BALF cellular composition and culture results between patients who were successfully weaned from MV within 28 days and those who were not. Respiratory mechanics before and after BALF collection were also evaluated. Results: BALF analysis revealed a mixed cellular pattern with a median total cell count of 174/μL (interquartile range [IQR], 104-400/μL). The successfully weaned group showed significantly higher macrophage percentages (24.7% vs. 3.5%, p = 0.034) and counts (56.4 vs. 10.5/μL, p = 0.024) than did the failure group. The failure group had higher neutrophil proportions (34.4% vs. 8.5%, p = 0.098). Positive cultures were found in 42.9% of patients. No deterioration in respiratory mechanics was observed after BALF. Conclusions: BALF analysis revealed a mixed cellular pattern. The successfully weaned group had significantly higher macrophage percentages and counts. BALF examination can be safely performed in patients with severe COVID-19.