Tracheal gas insufflation.
Tracheal gas insufflation (TGI) is an adjunct to mechanical ventilation that reduces CO (2) present in the anatomic deadspace. This is accomplished by flowing fresh gas (typically 6-10 lpm) directly into the trachea via a catheter placed into the endotracheal tube positioned at the distal end or by an embedded catheter in the wall of a specially designed endotracheal tube. This is thought to improve gas mixing because of the turbulent flow created at the tip of the catheter. There are two methods of gas flow delivery and cycling. Gas flow may be delivered directly toward the carina or in a reverse flow fashion. Cycling of TGI flow may be just during exhalation or during both inhalation and exhalation. A system integrated into the monitoring and controls of a mechanical ventilator could eventually prove the safest and most effective. However, currently there are no FDA-approved devices for TGI administration. It is critical to monitor the adverse effects (triggering, auto-PEEP [positive end expiratory pressure], air trapping, and patient comfort) created by the additional flow introduced into the ventilator circuit, while balancing the CO (2) clearance. There are limited data, mostly from animal studies. However, the trials done in both animal and humans are promising with regard to effective CO (2) elimination and avoidance of unacceptably high peak airway pressures. Available equipment has limited studies with infants. Even within the adult population, much work needs to be done to determine the optimal catheter position, the most appropriate TGI flow characteristics, and improve the safety of TGI.
McConnell
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R
Duke University Medical Center, Durham, North Carolina 27710, USA.
MacIntyre
N R
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