Continuous and Expiratory Tracheal Gas Insufflation Produce Equal levels of Total Peep

Abstract

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 $\left({\dot{V}}_E\right)$ , at 3 different inspiratory-expiratory ratios.

Results

Under constant ${\dot{V}}_E$ conditions, the increase in total PEEP was equivalent with c-TGI and e-TGI. Without adjustments to maintain ${\dot{V}}_E$ constant, ${\dot{V}}_E$ increased during c-TGI and decreased during e-TGI. Under all conditions increasing the inspiratory-expiratory ratio increased total PEEP.

Conclusion

When ${\dot{V}}_E$ 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.