Asymmetry in lung pathology and short-term effects of independent lung ventilation (ILV) on pulmonary mechanics and gas exchange in patients with blunt chest trauma

Independent lung ventilation has been used in patients with asymmetric lung pathology. In this study we applied ILV in 17 consecutive ventilated patients with blunt chest trauma with inclusion criteria PO₂/FiO₂ < 200 without physical or roentgenographic evidence of unilateral pulmonary disease. Eight of the patients (53%) demonstrated paradoxical PEEP/CPAP effect (worsening of pulmonary mechanics, gas exchange and increase in shunt with PEEP application) before institution of ILV. After application of ILV 10 of the patients (59%) demonstrated pulmonary mechanics asymmetry between left and right lung. In this group of patients we continued with ILV and applied differential PEEP levels (3.4 ± 2.2 cmH₂O for normal lung and 12 ± 3.7 for diseased lung, optimized with constant flow technique) with different tidal volumes for both lungs and level of Pplat < 30 cmH₂O. Pulmonary mechanics, gas exchange and total body oxygen delivery were determined on 1, 6 and 48 hours after ILV application. In patients who did not demonstrate pulmonary asymmetry we replaced ILV with conventional mechanical ventilation. Patients with continued ILV demonstrated significant improvement in oxygenation parameters and total body oxygen delivery and gradually decreasing asymmetry in pulmonary mechanics. In this study we found high incidence (59% of patients) of lung pathology asymmetry in patients with blunt chest trauma without roentgenographic or physical evidence of such asymmetry. Our data suggest that ILV can be used in patients with blunt chest trauma as lung protective ventilatory strategy with maximal favourable effect on diseased lung and minimal adverse effect on normal lung.