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

Abstract

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 (V t) while limiting CO 2 retention. We tested the extent to which panexpiratory TGI allows reduction of V t while maintaining Paco 2 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 V t-sparing effect of TO was tested by progressively increasing catheter flow rate (Vc) from 2 to 5, 10, and 15 L/min while decreasing V t by an amount that maintained Paco 2 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 V t was associated with a decrement in peak and end-inspiratory plateau airway opening pressure from 32 ± 3 to 28 ± 6 cm H 2O and from 25 ± 2 to 21 ± 3 cm H 2O, 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, Pao 2, or pulmonary venous admixture. Conclusion: We conclude that TO can be a useful adjunct to CMV during acute lung injury to limit V t while avoiding CO 2 retention.