Impairment of carotid artery blood flow by supraglottic airway use in a swine model of cardiac arrest
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OBJECTIVE: Supraglottic airway devices (SGDs) are often used as an alternative to endotracheal tube (ETT) during cardiopulmonary resuscitation (CPR). SGDs can be inserted 'blindly' and rapidly, without stopping compressions. These devices utilize pressurized balloons to direct air to the trachea and prevent esophagus insufflation. We hypothesize that the use of a SGD will compress the carotid artery and decrease carotid blood flow (CBF) during CPR in pigs. METHODS: Ventricular fibrillation (VF) was induced in 9 female pigs (32 +/- 1 kg) followed by 4 min without compressions. CPR was then performed continuously for 3-6-min intervals. During each interval, an ETT was used for the first 3 min, followed by 3 min of each SGD (King LTS-D, LMA Flexible, Combitube) in a random order. The primary endpoint was mean CBF (ml/min). Statistical comparisons among the 4 airway devices were performed by Wilcoxon Rank test. Post mortem carotid arteriographies were performed with SGDs in place. RESULTS: CBF (median ml/min; 25/75 percentile) was significantly lower with each SGD [King (10; 6/41), LMA (10; 4/39), and Combitube (5; -0.4/15)] versus ETT (21; 14/46) (p<0.05 for each SGD compared with ETT). Arteriograms showed that with each SGD there was compression of the internal and external carotid vessels. CONCLUSION: The use of 3 different SGDs during CPR significantly decreased CBF in a porcine model of cardiac arrest. While the current study is limited to pigs, the findings suggest that further research on the effects of SGD use in humans and the effects on carotid artery blood flow is warranted.
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