Abstract 2: Automated Detection of Breathing and Pulse Pressure During Cardiac Arrest
Introduction One size does not fit all. We therefore sought to automatically differentiate between dysrhythmic and asphyxial cardiac arrest and prompt the rescuer accordingly. We utilized impedance measurements indicative of breathing and of pulse pressure for differentiating between these two disparate causes of cardiac arrest and prompt priority interventions accordingly.
Methods ECG and transthoracic impedance were measured with conventional AED sensing and defibrillation electrodes. Adaptive filtering allowed for quantification of both changes in thoracic impedance due to breathing and changes that reflected the mechanical heart beat.
Results A total of 5 comprehensive recordings were obtained on a pig model of asphyxial arrest. The changes in cardiac impedance were highly correlated with pulse pressure (R2 = 0.95, Figure 1⇓). A discrete respiratory impedance signal was highly correlated with tidal volume ( R2 = 0.91).
Conclusion Impedance detection may be incorporated into AEDs as a measurement combined with the ECG for ventilation and pulse pressure estimation during cardiac arrest. The absence of a pulse is provisionally identified when pulse pressure (systolic-diastolic) is less than 20 mmHg (cardiac impedance < 0.037 ohms). Such would prompt initial precordial compression and defibrillaiton. Restraints in breathing and especially asphyxia are defined by tidal volumes < 20% of minimal adult/pediatric resting values (thoracic impedance < 0.8 ohms) in association with a reduced slope of the thoracic impedance signal and such would prompt priority airway and ventilation interventions.