Background

Neutrophil extracellular traps have been associated with tissue damage. Whether these are involved in the pathogenesis of human acute respiratory distress syndrome (ARDS) and could be a potential therapeutic target is unknown. The authors quantified bronchoalveolar and blood neutrophil extracellular traps in patients with pneumonia-related ARDS and assessed their relationship with ventilator-free days.

Methods

Immunocompetent patients with pneumonia and moderate or severe ARDS (n= 35) and controls (n= 4) were included in a prospective monocentric study. Neutrophil extracellular trap concentrations were quantified (as DNA-myeloperoxidase complexes) in bronchoalveolar lavage fluid and serum by enzyme-linked immunosorbent assay. The relationship between bronchoalveolar lavage neutrophil extracellular trap concentrations and the primary clinical endpoint (ie, the number of live ventilator-free days at day 28) was assessed using linear regression analyses.

Results

There was no significant relationship between bronchoalveolar lavage neutrophil extracellular trap concentrations and ventilator-free days by multiple regression analysis (β coefficient= 2.40; 95% CI,-2.13 to 6.92; P= 0.288). Neutrophil extracellular trap concentrations were significantly higher in bronchoalveolar lavage than in blood of ARDS patients (median [first to third quartiles]: 154 [74 to 1,000] vs. 26 [4 to 68] arbitrary units, difference:-94; 95% CI,-341 to-57; P< 0.0001). Bronchoalveolar concentrations of patients were higher than those of controls (154 [74 to 1,000] vs. 4 [4 to 4] arbitrary units, difference:-150; 95% CI,-996 to-64; P< 0.001) and associated with bronchoalveolar interleukin-8 (Spearman's ρ= 0.42; P= 0.012) and neutrophil concentrations (ρ= 0.57; P< 0.0001). Intensive care unit mortality (12%, n= 2 of 17 vs. 17%, n= 3 of 18; P> 0.99) and the number of ventilator-free days at day 28 (22 [14 to 25] vs. 14 [0 to 21] days; difference:-5; 95% CI,-15 to 0; P= 0.066) did not significantly differ between patients with higher (n= 17) versus lower (n= 18) bronchoalveolar neutrophil extracellular trap concentrations.

Conclusions

Bronchoalveolar neutrophil extracellular trap concentration was not significantly associated with mechanical ventilation duration in pneumonia-related ARDS.