Background: Pseudo-pulseless electrical activity (pseudo-PEA) is a pathophysiological state where the heart is beating but the patient’s pulse is not palpable due to severe hypotension. Patients may present with this physiology due to ongoing hypoxia or ischemia, or after a successful conversion from ventricular fibrillation. While chest compressions are recommended for these patients, but the interaction between chest compressions and the intrinsic heart beat remains poorly understood.
Methods: 11 swine (~30 kg) underwent hypoxia (FiO2 = 6%) until pseudo-PEA was induced (systolic aortic pressure < 50 mmHg). Pseudo-PEA was treated with mechanical chest compressions (SCPR) for periods of 45 s (rate = 100 CPM, depth = 2”) or left untreated for periods of 45 s. Multiple rounds of SCPR were performed in each animal and the order was randomized. Aortic pressure, right atrial pressure, and carotid and jugular blood flows were measured continuously.
Results: There were no statistically significant differences in blood pressures and blood flows between untreated pseudo-PEA and pseudo-PEA treated with SCPR when compared by t-tests. Blood pressure and flow results are shown in Table 1.
Table 1: Hemodynamics during untreated pseudo-PEA and pseudo-PEA treated with SCPR
MAP RAP Jugular Flow Carotid Flow
mmHg mmHg mL/min mL/min
P-EMD 30.1±3.3 4.6±0.8 4.4±11 73.5±57
SCPR 29.1±2.3 4.7±0.8 2.7±14 48.1±48
Differences in the intrinsic heart rate and the chest compression rate produced a spectrum of blood flows and pressures that spanned from improved to impaired hemodynamics as shown in Figure 1.
Conclusion: During pseudo-PEA, SCPR did not improve blood pressures or carotid or jugular flows. Because chest compressions were not always delivered during systole, the chest compression improved hemodynamics, had minimal effect, or impaired hemodynamics, leading to a net neutral result.