Inspiratory tidal volume sparing effects of tracheal gas insufflation in dogs with oleic acid-induced lung injury

Purpose: Tracheal gas insufflation (TGI) improves the efficiency of conventional mechanical ventilation (CMV) by reducing the series dead space of the airways. Consequently, application of TO as an adjunct to CMV may permit reducing tidal volume (Vt) while limiting CO₂ retention. We tested the extent to which panexpiratory TGI allows reduction of Vt while maintaining Paco₂ constant in an oleic acid-induced lung injury model. Methods: We studied six anesthetized, paralyzed, and mechanically ventilated dogs. Oleic acid injury was induced by injecting 0.09 mL/kg of oleic acid into the right atrium. After stabilization of lung injury the Vt-sparing effect of TO was tested by progressively increasing catheter flow rate (Vc) from 2 to 5, 10, and 15 L/min while decreasing Vt by an amount that maintained Paco₂ constant (≈47 mm Hg) with respect to baseline (Vc = 0 L/ min). Results: Tidal volume was decreased from a baseline value of 0.360 ± 0.030 L to 0.238 ± 0.054 L at Vc of 15 L/min. The reduction in Vt was associated with a decrement in peak and end-inspiratory plateau airway opening pressure from 32 ± 3 to 28 ± 6 cm H₂O and from 25 ± 2 to 21 ± 3 cm H₂O, respectively. Total physiological dead space fraction decreased from a baseline value of 0.60 ± 0.08 to 0.31 ± 0.20 during TGI at 15 L /min. TGI did not affect cardiac output, Pao₂, or pulmonary venous admixture. Conclusion: We conclude that TO can be a useful adjunct to CMV during acute lung injury to limit Vt while avoiding CO₂ retention.