Low-Flow Transtracheal Rescue Insufflation of Oxygen After Profound Desaturation

A Resuscitation Option for Upper Airway Occlusion Based on Bolus Transtracheal Lung Inflation

Background

Acute laryngospasm sufficient to cause obstructive apnea is a medical emergency that can be difficult to manage within the very short time available for establishing an airway. We have presented substantial evidence that laryngospasm-based obstructive apnea is the cause of sudden death in epilepsy, and airway management is particularly challenging during seizure activity.

Objective

We sought to determine if the transtracheal delivery of a bolus of oxygen or room air below the level of an obstruction to inflate the lungs could be an effective method to prolong the time available for responders seeking to establish a stable airway, and, if so, what could be learned about optimization of delivery parameters from a rat model.

Methods

Rats were fitted with a t-shaped tracheal tube for controlling access to air and for measuring airway pressures. After respiratory arrest from simulated laryngospasm, bolus transtracheal lung inflation with a volume of gas equivalent to half the vital capacity was delivered to the closed respiratory system as the only resuscitation step.

Results

Bolus lung inflation was sufficient for resuscitation, improving cardiac function and re-establishing adequate oxygen status to support life. Inflation steps could be repeated and survival times were approximately 3 times that of non-inflated lungs.

Conclusion

The properties and consequences of bolus lung inflation are described as a foundation for procedures or devices that can be useful in cases of severe laryngospasm and other cases of upper airway obstruction.

Level of Evidence

3.

Novel use of a portable ventilation device with low-flow tracheal insufflation of oxygen in a Swine model

INTRODUCTION

Mechanical ventilation of intubated patients is standard to meet oxygenation and ventilation goals. This can require significant energy and oxygen resources. In military operations and mass casualty disasters, oxygen conserving strategies may be important. Low flow tracheal insufflation of oxygen (TRIO) is a technique that provides adequate oxygenation while conserving oxygen during apnea. This technique, however, is limited by increases in carbon dioxide (CO2) when used for extended periods. The addition of passive pressure release ventilation could potentially improve CO2 elimination and the acceptance of this technique. The purpose of this study was to determine whether TRIO combined with the novel configuration of a portable ventilator used to provide passive pressure release ventilation improves CO2 levels during apneic oxygenation.

METHODS

Animals (n = 7) were anesthetized, paralyzed, and intubated. Oxygen (O2) was insufflated through the capillary lumen of the Boussignac endotracheal tube at 2 L/min. The low flow O2 was the only source of power and gas for ventilation. A modified Oxylator EMX transport ventilator connected to the endotracheal tube was configured to release when pressure in the subjects lungs reached 30 cm H2O. No electrical or pneumatic sources were required. Hemodynamic measurements and arterial blood gases were taken at various intervals for 2 hours.

RESULTS

All pigs remained adequately oxygenated with Pao2 >390 mm Hg in all subjects at every blood gas measurement and survived the 2-hour experiment. Baseline Paco2 (43 +/- 4 mm Hg) increased and pH (7.48 +/- 0.03) decreased to 72 +/- 5 mm Hg and 7.29 +/- 0.02 at 1 hour and 83 +/- 8, 7.24 +/- 0.03 at 2 hours. This is significantly less than would be expected during apnea over this time period. Hemodynamic measurements remained stable.

CONCLUSION

The combination of low flow TRIO with a modified Oxylator in this novel configuration provides acceptable Pao2, Paco2, and hemodynamic parameters for 2 hours in apneic swine. This could be a valuable technique in situations where oxygen and power are limited.