Experimental study of high-frequency two-way jet ventilation

A new tracheal tube and methods to facilitate ventilation and placement in emergency airway management

The "jet endotracheal tube" (JET) has been designed to facilitate emergency intubation in apnoeic or paralyzed patients with a difficult airway. We investigated the efficiency of jet ventilation to maintain adequate oxygenation and ventilation using the initially designed JET, either with its distal tip positioned above vocal cord and pointed directly at or 45 degrees to the right of the vocal cord opening midline in 10 adult paralyzed pigs. The effectiveness of using end tidal carbon dioxide pressure (PetCO(2)), chest rise and breath sounds to facilitate tracheal placement of the JET blindly in a simulated difficult airway was studied. All complications of using the JET were noted. Jet ventilation with the distal tip of the JET pointed directly at, not 45 degrees to the right of vocal cord opening midline, provides adequate oxygenation and ventilation during intubation. In a simulated difficult airway, PetCO(2), chest rise and breath sounds were all effective methods to assist placement of the JET blindly, and the combination of all three methods works the best. No serious complications were detected with the use of the JET. Our results suggest that a correctly positioned JET guided by monitoring PetCO(2), chest rise and breath sound provides adequate oxygenation and ventilation during intubation in apnoeic pigs, and facilitates the intubation blindly in a simulated difficult airway. No serious complications were observed using the JET in this study. In patients requiring emergency intubation, a JET with PetCO(2) monitoring catheter and the instructions for use may be a useful addition to the airway management devices.

Experimental study of double-lumen, two-stage endotracheal tube during conventional mechanical ventilation in rabbits

OBJECTIVE

To evaluate the effects of a double-lumen, two-stage endotracheal tube on gas exchanges (ventilatory efficiency) during conventional mechanical ventilation, using a ventilator in rabbits.

DESIGN

Prospective, randomized, crossover laboratory animal trial.

SETTING

Research laboratory in the Beijing Children's Hospital.

SUBJECTS

Five adult New Zealand rabbits, weighing 3.2 to 3.7 kg.

INTERVENTIONS

A new type of endotracheal tube-the double-lumen two-stage endotracheal tube-was designed and tested for ventilation efficiency in rabbits with normal and injured lungs. The new tube (size 3.0 mm) was made out of two Portex endotracheal tubes (size 3.0 mm) by adhering two vertical cross-sections at the distal end of the two tubes. The new tube and a conventional endotracheal tube of the same size (inner diameter 3.0 mm) were randomly used in pressure control ventilation. Each trial was maintained for 30 mins.

MEASUREMENTS AND MAIN RESULTS

Effects from the two endotracheal tubes on pulmonary mechanics, hemodynamics, and gas exchange were observed. We measured peak inspiratory pressure, positive end-expiratory pressure (PEEP), intrinsic PEEP, mean airway pressure, and arterial blood and mixed expired gas variables (Pao2, Paco2, pH, and mixed expired gas Pco2). The new endotracheal tube acutely increased CO2 elimination in all animals with normal and injured lungs. Paco2 decreased from 46 +/- 4 to 36 +/- 5 torr (6.1 +/- 0.5 to 4.8 +/- 0.7 kPa; p < .01) in normal lungs and from 48 +/- 5 to 36 +/- 5 (6.4 +/- 0.7 to 4.8 +/- 0.7 kPa; p < .01). Meanwhile, tidal volume fraction decreased from 0.48 +/- 0.07 to 0.35 +/- 0.05 (p < .01) and from 0.56 +/- 0.07 to 0.40 +/- 0.07 (p < .01) in normal and injured lungs, respectively. Intrinsic PEEP of the new tube slightly increased, but there were no significant differences in comparison with the conventional tube.

CONCLUSION

Compared with the conventional endotracheal tube, the new double-lumen, two-stage endotracheal tube reduced Paco2 by decreasing anatomical deadspace in rabbits with normal and injured lungs under pressure control ventilation, thus enhancing ventilatory efficiency and reducing ventilator-induced injury.