Tracheal gas insufflation.

Tracheal gas insufflation (TGI) is an adjunctive ventilatory technique that delivers fresh gas into the trachea either continuosly or only during a specific segment of the respiratory cycle (phasic flow) [ 1 , 2 , 3 , 4 ]. Two mechanisms are responsible for improving the efficacy of conventional tidal breaths during TGI [ 5 , 6 , 7 ]. First, fresh gas introduced by the catheter during expiration flushes the series (anatomic) deadspace compartment proximal to its tip free of CO 2 . Consequently, during the subsequent inspiration, less CO 2 is recycled back to the alveoli thus improving CO 2 elimination. Second, at high catheter flow rates, turbulence generated at the tip of the catheter can enhance gas mixing in regions distal to the catheter tip, thereby contributing to CO 2 removal.