Continuous and expiratory tracheal gas insufflation produce equal levels of total PEEP

BACKGROUND: Tracheal gas insufflation (TGI) used in conjunction with mechanical ventilation can increase total positive end-expiratory pressure (total PEEP). We tested the theory that TGI delivered throughout the entire respiratory cycle (c-TGI) increases total PEEP more than expiratory phase TGI (e-TGI). We also studied whether a pressure relief valve in the ventilator circuit could prevent increase in total PEEP during TGI. METHODS: Using an artificial lung model and pressure control ventilation, we studied the effect of c-TGI and e-TGI, with and without a pressure relief valve, and with and without maintenance of a constant minute ventilation (V̇(E)), at 3 different inspiratory-expiratory ratios. RESULTS: Under constant V̇(E) conditions, the increase in total PEEP was equivalent with c-TGI and e-TGI. Without adjustments to maintain V̇(E) constant, V̇(E) increased during c-TGI and decreased during e-TGI. Under all conditions increasing the inspiratory- expiratory ratio increased total PEEP. CONCLUSION: When V̇(E) is maintained constant, c-TGI and e-TGI produce equivalent levels of total PEEP. Failure to adjust the ventilator settings during TGI creates changes in ventilatory parameters that are unique to each delivery system