Application of tracheal gas insufflation to acute unilateral lung injury in an experimental model

In unilateral lung injury, application of global positive end-expiratory pr essure (PEEP) may cause overdistension of normal alveoli and redistribution of blood flow to diseased lung areas, thereby worsening oxygenation. We hy pothesized that selective application of tracheal gas insufflation (TGI) wi ll recruit the injured lung without causing overdistension of the normal lu ng. In eight anesthetized dogs, left lung saline lavage was performed until Pa-O2/Fi(O2) fell below 100 mm Hg. Then, the dogs were reintubated with a Univent single lumen endotracheal tube that incorporates an internal cathet er to provide TG I. After injury, increasing PEEP from 3 to 10 cm H2O did n ot change gas exchange, hemodynamics, or lung compliance. Selective TGI, wh ile keeping end-expiratory lung volume (EELV) constant, improved Pa-O2/Fi(O 2) from 212 +/- 43 to 301 +/- 38 mm Hg (p < 0.01) while Pa-CO2 and airway p ressures decreased (p < 0.01). During selective TGI, reducing tidal volume to 5.2 ml/kg while keeping EELV constant, normalized Pa-CO2, did not affect Pa-O2/Fi(O2), and decreased end-inspiratory plateau pressure from 16.6 <pl us/minus> 1.0 to 11.9 +/- 0.5 cm H2O (p < 0.01). In unilateral lung injury, we conclude that selective TGI (1) improves oxygenation at a lower pressur e cost as compared with conventional mechanical ventilation, (2) allows red uction in tidal volume without a change in alveolar ventilation, and (3) ma y be a useful adjunct to limit ventilator-associated lung injury.