Tracheal insufflation of oxygen at low flow : capabilities and limitations

Tracheal insufflation of oxygen (TRIO) may provide temporary oxygenation for patients or sustain life in apneic mass casualties when conventional ventilatory techniques are not available or feasible. Logistically, minimum flows of TRIO (Vmin) are desirable for field use and to reduce barotrauma should airway obstruction occur. We carried out a feasibility study to determine the efficacy of Vmin of TRIO delivered within 1 cm of the carina, in nine anesthetized and paralyzed dogs. Minimum flows of TRIO for these dogs of average weight (12 kg) was 91 mL/min. In six of the dogs Vmin TRIO was continued and provided oxygenation for an average of 1.5 h compatible with subsequent resuscitation with conventional ventilation. However, PaCO2 levels increased to mean values of 256 mm Hg in the 90 min. To determine what the effect of increased gas mixing was on gas exchange, we repeated Vmin TRIO for 10 min in six of the dogs with and without high frequency oscillations superimposed on the TRIO flow. The oscillations (60 mL at 16.3 Hz) increased carbon dioxide excretion but significantly impaired oxygenation. In completely apneic animals, TRIO at low flow delivered by cricothyroidotomy may be useful as an emergency procedure when upper airway obstruction limits the use of other airway management techniques. However, enhancement of gas mixing during low-flow TRIO impairs oxygenation, so that higher flows would be required when respiratory efforts occur.