Abstract 94: A Novel, Hands-free, Non-invasive Doppler Ultrasound Device Detects Pseudo-Pulseless Electrical Activity in a Swine Model of Cardiac Arrest
Background: Without invasive monitoring, conditions of low cardiac output during resuscitation from cardiac arrest remain unrecognized. Distinguishing pseudo-PEA, a condition with measurable cardiac output but clinically undetectable blood pressure, from true-PEA continues to be a challenge.
Hypothesis: A novel hands-free, non-invasive Doppler ultrasound device will differentiate pseudo-PEA from true-PEA during resuscitation from cardiac arrest by measuring carotid blood flow.
Methods: Five anesthetized, intubated swine were instrumented with aortic (Ao) and right atrial pressure transducing catheters. The Doppler device was adhered to the neck over the carotid artery. Continuous EKG, pressure readings, and Doppler signal were digitized to disk. A ventricular pacing catheter was used to induce ventricular fibrillation. Several fibrillation and resuscitation cycles were performed in each animal. All episodes of true and pseudo-PEA were identified by EKG and Ao waveforms. True-PEA was defined as EKG complexes with an Ao waveform change of <5 mmHg. Pseudo-PEA was defined by EKG complexes with an Ao systolic waveform ≥ 5 but < 60mmHg. The sensitivity and specificity of the device to detect pseudo-PEA was obtained using observers blinded to Ao waveform recordings.
Results: There were 8 pseudo-PEA events identified between 2 animals during the resuscitations. The blinded observers were able to recognize 7 of the 8 episodes (sensitivity=0.875, specificity=0.846). Four false positives of 26 true-PEA events were reported due to the device sensing changes in pulse pressure of 2–4 mmHg from baseline. There was good correlation of the Ao systolic blood pressure with peak systolic Doppler frequency for the two animals (R1=0.89, R2=0.71, respectively).
Conclusions: This hands-free, noninvasive Doppler device can reliably differentiate pseudo-PEA from true-PEA during resuscitation from cardiac arrest.