Airway protection during experimental CPR

Experimental studies recently demonstrated that positive pressure ventilation may not be essential for initial cardiopulmonary resuscitation. Nevertheless, oxygen enrichment of inspired gas mixtures and spontaneous gasping were associated with increased resuscitability and survival after cardiac arrest. However, as yet unresolved is the benefit of early airway control under conditions simulating "sudden death" due to ventricular fibrillation.

Twenty adult, male Sprague-Dawley rats were randomly assigned to one of two groups in which the airway was unprotected or protected by an oropharyngeal airway of our design. Cardiac arrest was induced by an alternating current delivered to the right ventricular endocardium. Oxygen was delivered to a hood that was loosely applied over the head of the each animal at a flow rate of 1 L/min. Precordial compression was initiated after 4 min of untreated ventricular fibrillation and defibrillation was attempted 6 min later. After spontaneous circulation had been restored, a tracheostomy was performed and the animals were mechanically ventilated with 100% oxygen for an additional interval of 1 h. Animals were then returned to their cages and observed for an additional 24 h.

Spontaneous circulation was restored in each of the animals who had an oropharyngeal airway and nine of ten animals in the absence of an artificial airway. In each group, seven animals survived for more than 24 h. Animals in which the airway had been protected had significantly greater frequency of spontaneous gasping (28 +/- 13/min vs 13 +/- 9/min; p < 0.05) and significantly higher arterial oxygen saturation (77 +/- 19% vs vs 55 +/- 25%; p < 0.05).

In the setting of experimental cardiac resuscitation, the insertion of an artificial airway increased the frequency of spontaneous gasping and arterial oxygenation. Nevertheless, no significant differences in resuscitability or postresuscitation survival were associated with insertion of the artificial airway.