High tidal volume ventilation does not exacerbate acid-induced lung injury in infant rats

The impact of mechanical ventilation with high V(T)-low PEEP in infant rats with preinjured lungs is unknown. After tracheal instillation of saline or acid, two week old rats were ventilated with V(T) 7 mL/kg and PEEP 5 cm H₂O or V(T) 21 mL/kg and PEEP 1cm H₂O for 4 h. Airway resistance and the coefficient of tissue elastance, measured via low-frequency forced-oscillation technique, and quasi-static pressure-volume curves deteriorated less with high V(T)-low PEEP when compared with low V(T)-high PEEP. IL-6 concentration in bronchoalveolar lavage fluid (BALF) did not differ between all ventilated groups. Moreover, differences in BALF protein concentration and histological lung injury scores were independent of applied ventilation strategies. In contrast to experimental studies with adult rats, short-term mechanical ventilation with high V(T)-low PEEP is not deleterious when compared to low V(T)-high PEEP in both healthy and pre-injured infant rat lungs. Our results call for caution when extrapolating data from adult studies and highlight the need for age-specific animal models.