• Keith A Marill, James J Menegazzi, Jorge A Gumucio, Rameen Forghani, and David D Salcido.
• Department of Emergency Medicine, Massachusetts General Hospital, Harvard Medical School.
• Prehosp Emerg Care. 2025 Feb 7: 191-9.

ObjectivesPulseless electrical activity (PEA) arrest, which includes pseudo-PEA, is increasingly common and survival remains dismal. We hypothesized that mechanical chest compressions synchronized to native cardiac contractions improve coronary perfusion pressure (CPP) during pseudo-PEA resuscitation.MethodsWe developed a model of pseudo-PEA by infusing high dose esmolol intravenously into anaesthetized, intubated, and central arterial and venous catheterized swine to a goal of 45 mm Hg mean arterial blood pressure (MAP). We performed a randomized unblinded repeated crossover trial by administering alternating synchronized and unsynchronized chest compressions for 52 seconds preceded by 8 second breaks consecutively 4 times. We repeated the protocol approximately 4 times with 1 minute breaks. Synchronized compressions were provided 1:1 with native contractions during systole and unsynchronized compressions were provided at 100 beats per minute (BPM). We measured average CPP, MAP, and heartrate (HR) for 5 beats immediately preceding the chest compression onset and for 30 seconds 10 seconds after compression onset. We computed the difference in continuous CPP during compressions compared to the immediately preceding baseline for each interval. We developed a mixed linear model with outcome average CPP during compressions minus baseline, fixed variable compression type, and random variable animal.ResultsWe included 6 animals. Mean baseline HR was 76.0 BPM, MAP 49.9, and CPP 36.2. Chest compressions increased CPP from baseline an average 1.7 mm Hg when unsynchronized and 5.6 mm Hg synchronized. The adjusted difference was 4.0 mm Hg (95% CI 2.4-5.5).ConclusionsSynchronized chest compressions increased CPP 4.0 mm Hg (135%) more than unsynchronized compressions despite a lower compression rate in medication-induced pseudo-PEA. Further refinement and eventual application to patients suffering pseudo-PEA arrest appear warranted.

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