Spontaneous Agonal Respiration in a Swine Model of Out-of-hospital Cardiac Arrest

Authors

  • James J. Menegazzi PhD,

    Corresponding author
    1. Center for Emergency Medicine of Western Pennsylvania, Pittsburgh, PA
    2. University of Pittsburgh School of Medicine, Pins burgh. PA, Division of Emergency Medicine
    • Center for Emergency Medicine, 230 McKee Place, Suite 500, Pittsburgh, PA 15213.

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  • Brian D. Check BS, EMT-P

    1. Center for Emergency Medicine of Western Pennsylvania, Pittsburgh, PA
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ABSTRACT

Objective: To describe ventilator dynamics following the onset of ventricular fibrillation (VF) in an experimental swine model.

Methods: Twelve female mixed-breed domestic swine (mean mass 21.3 2 1.7 kg) were sedated with IM ketamine (10 mag) and xylazine (1 mgntg), anesthetized with α-chloralose (40 mgkg loading dose, 10 mg/kg/hr rnaintenance infusion), incubated, and mechanically ventilated on room air. ECG, and aortic and pulmonary artery pressures were monitored continuously. VF was induced with a 3-sec, 60-Hz, 100-mA Tran thoracic shock, and left untreated for 8 minutes. Respiratory rate, tidal volume, and minute ventilation were recorded until respiratory activity ceased.

Results: 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 breathdmin. Mean tidal volumes ranged from 502 to 852 mL. Mean minute ventilations ranged from 3.3 to 5.8 L.

Conclusion: In this swine model, 11 of 12 (92%) continued to have spontaneous agonal respirations for the first 3 minutes of VF cardiac arrest. Many animals had supernormal tidal volumes, and near-normal minute ventilations. These findings have potential implications for lay-rescuer and first-responder contributions to resuscitation of victims of out-of-hospital cardiac arrest.

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