Tracheal gas insufflation reduces the tidal volume while PaCO2 is maintained constant

Abstract

Objective: The aims of the present study were two-fold: first, to confirm the effect of tracheal gas insufflation (TGI) throughout the respiratory cycle on alveolar ventilation at various catheter flows and constant total inspired VT as an adjunct to conventional volume cycled mechanical ventilation in patients with acute lung injury; second, to test the efficacy of TGI in the reduction of toal VT, peak and mean airway pressure while maintaining PaCO2 in its baseline value. The hemodynamic effect and the consequences on oxygenation as result of the reduction of VT, were also estimated. Design: Prospective study of patients with acute lung injury requiring mechanical ventilation. Setting: 12 bedded, adult polyvalent intensive care unit in a teaching hospital. Patients: 7 paralyzed and sedated patients with acute respiratory failure were studied. All patients were clinically and hemodynamically stable without fluctuation of the body temperature. All patients were orally intubated with cuffed endotracheal tubes, and mechanically ventilated with a standard circuit of known compliance. Interventions: Continuous flows (4 and 6 l/min) were delivered through a catheter positioned 1 cm above carina while tidal volume or PaCO2 were maintained constant at their baseline value. Results: In this study a modest level of TGI significantly enhanced CO2 elimination in patients with acute respiratory failure. Improved ventilatory efficiency resulted from the functional reduction of dead space during TGI allowing the same PaCO2 to be maintained at the same frequency with lower tidal volume and lower airway pressure requirement. Tidal volume, peak and mean airway pressure decreased linearly with catheter flow, without significant changes in oxygenation, while PaCO2 remained stable. Conclusion: The results of this study suggest that TGI may be an useful adjunct mode of mechanical ventilation that limits alveolar pressure and minute ventilation requirements. © 1994 Springer-Verlag.