SPONTANEOUS AGONAL RESPIRATION IN A SWINE MODEL OF OUT-OF-HOSPITAL CARDIAC-ARREST

Objective: To describe ventilatory dynamics following the onset of ven tricular fibrillation (VF) in an experimental swine model. Methods: Tw elve female mixed-breed domestic swine (mean mass 21.3 +/- 1.7 kg) wer e sedated with IM ketamine (10 mg/kg) and xylazine (1 mg/kg), anesthet ized with alpha-chloralose (40 mg/kg loading dose, 10 mg/kg/hr mainten ance infusion), intubated, and mechanically ventilated on room air. EG G, and aortic and pulmonary artery pressures were monitored continuous ly. VF was induced with a 3-sec, 60-Hz, 100-mA transthoracic shock, an d left untreated for 8 minutes. Respiratory rate, tidal volume, and mi nute ventilation were recorded until respiratory activity ceased. Resu lts: All 12 animals (100%) had agonal respirations through the first 2 minutes of arrest. This decreased to 11 (92%) at minute 3, five (42%) at minute 4, and two (17%) at minute 7. Mean respiratory rates ranged from 6 to 11 breaths/min. Mean tidal volumes ranged from 502 to 852 m L. Mean minute ventilations ranged from 3.3 to 5.8 L. Conclusion: In t his swine model, 11 of 12 (92%) continued to have spontaneous agonal r espirations for the first 3 minutes of VF cardiac arrest. Many animals had supranormal tidal volumes, and near-normal minute ventilations. T hese findings have potential implications for lay-rescuer and first-re sponder contributions to resuscitation of victims of out-of-hospital c ardiac arrest.