Objective: Respiratory syncytial virus lower respiratory tract infection is the most frequent cause of respiratory insufficiency necessitating mechanical ventilation in infants during the winter season. Recently, we presented a new animal model to show that mechanical ventilation aggravates respiratory syncytial virus-induced pulmonary inflammation by distinct mechanisms. We now use this model to study whether low tidal volume mechanical ventilation causes less ventilator-induced lung injury in the presence of respiratory syncytial virus lower respiratory tract infection.
Design: Randomized controlled experimental study.
Setting: University Medical Center animal laboratory.
Subjects: Male BALB/c mice, 6-8 weeks old and weighing 20-28 g.
Interventions: Mice were inoculated with respiratory syncytial virus or mock virus on day 0 and ventilated on day 1 or 5 with high (12 mL/kg) or low (6 mL/kg) tidal volume for 5 hours.
Measurements and main results: Total and differential cell counts as well as cytokine concentrations were determined in bronchoalveolar lavage fluid. Compared with nonventilated respiratory syncytial virus-infected mice, high tidal volume ventilation of respiratory syncytial virus-infected mice on day 5 enhanced bronchoalveolar lavage fluid total cell count (0.35 vs 0.99 × 10e6/mL; p < 0.01), neutrophils (0.02 vs 0.17 × 10e6/mL; p < 0.01), interleukin-6 (58 vs 250 pg/mL; p < 0.01), and keratinocyte-derived chemokine (95 vs 335 pg/mL; p < 0.01) levels. In low tidal volume ventilation of respiratory syncytial virus-infected mice, no significant difference in cell counts or cytokine concentrations was observed compared with spontaneous breathing respiratory syncytial virus-infected controls on both days.
Conclusions: Low tidal volume mechanical ventilation causes less ventilation-induced cellular and cytokine influx into the bronchoalveolar space during respiratory syncytial virus lower respiratory tract infection.