Abstract 189: How Quickly Does Arterial Blood Pressure Recover After Pauses in Mechanical Chest Compressions in Humans With Out-of-Hospital Cardiac Arrest?

Introduction: Conventional wisdom says that arterial blood pressure (ABP) recovers slowly after interrupting CPR chest compressions (CCs). An oft-cited animal study with manual compressions and 15:2 compression:ventilation ratio showed that all 15 compressions were needed to restore pre-pause invasive pressure, implying that even short pauses substantially reduce CPR blood flow. Whether this holds true for humans receiving mechanical chest compressions is unknown. We measured recovery of ABP after pauses in mechanical compressions by LUCAS in patients treated for out-of-hospital cardiac arrest (OHCA).

Methods: We analyzed data from a subset of patients enrolled in both groups of a prospective, randomized LUCAS 2 Active Decompression trial performed by an anesthesiologist-staffed rapid response car program in Oslo, Norway from 2016 to 2018. Only patients with an ABP signal and at least one CC pause longer than 2 sec were included. All CCs were mechanical. Arterial cannulation was verified, and CC pauses were identified by physician review of the patient care record and physiological signals. Pauses were excluded if ROSC or a LUCAS “soft start” occurred or epinephrine had been applied within 5 minutes of the pause. Peak compression (cAP), mean (mAP), and mean decompression arterial blood pressures (dAP) for 10 CCs before and after each pause were measured with custom MATLAB code.

Results: We included 56 patients with a total of 148 pauses (mean pause duration: 10.63 ± 3.05 sec). Pre-pause mean cAP, mAP, and dAP were 95.6 ± 0.3, 49.9 ± 0.1 and 30.5 ± 0.1 mmHg. Post-pause dAP for each compression was not significantly different than pre-pause dAP (Fig. 1A,B). cAP and mAP recovered to >90% of pre-pause pressure within 2 CCs. Pause duration was not predictive of post-pause pressures (Fig. 1C).

Conclusions: ABP generated by mechanical CPR recovered quickly after pauses. Consequently, short pauses (such as pauses for 30:2 CPR) may pose less hemodynamic concern than previously thought.