Abstract 163: Lung Inflation Occurs Infrequently In Most Patients During 30:2 CPR With Bag-Valve-Mask Ventilation

Abstract

Background: Few studies have measured ventilation early in cardiopulmonary resuscitation (CPR) before advanced airway placement. In 30:2 CPR, there is a pause to give two ventilations after each round of 30 chest compressions. Recently, we developed a method to identify lung inflation (ventilation) waveforms from thoracic bioimpedance defibrillator recordings measured through defibrillator pads. Early work showed that in 75% of patients receiving bag-valve-mask (BVM) ventilation, lung inflation waveforms occurred in less than half of pauses in chest compressions during 30:2 CPR. Objective: To determine the incidence of lung inflation with BVM during 30:2 CPR in a multi-center study. Methods: Our study included adult out-of-hospital cardiac arrest patients from five sites of the Resuscitation Outcomes Consortium Trial of Continuous or Interrupted Chest Compressions during CPR. Patients had 30:2 CPR with ≥ two minutes of thoracic bioimpedance signal recorded with a defibrillator (Lifepak, Physio-control, Redmond, WA or MRx, Philips, Andover, MA). Previously, we defined a ventilation waveform as having a bioimpedance amplitude ≥0.5 Ohm (corresponding to ≥ 250 ml Vt) with a duration ≥1 sec. A valid pause was 3 sec to 15 sec. An automated program analyzed the recordings. We describe groups with ventilation waveforms in <50% or ≥50% of pauses. Results: We included 1,552 patients; mean age was 66 years, 67% were male, mean (±SD) duration of 30:2 CPR was 9.9 ±5.8 min from the start of chest compressions until advanced airway placement. During this period there was a total of 21,705 pauses in chest compressions, a median of 12 pauses in chest compressions, and a median of 5 ventilations; 56% of patients had ventilation waveforms in <50% of pauses (Group 1, N=868), and 44% had waveforms in > 50% of pauses (Group 2, N=678). The median (IQR) number of pauses in Group 1 vs. Group 2, was 12 (8, 20) vs. 12 (7, 17) and the median number of ventilations was 3 (1, 6) vs. 13 (7, 21), respectively, during 30:2 CPR. The median duration of pauses for Group 1 vs. Group 2, was 5.8s (5.0, 6.5) vs. 5.7s (5.0, 6.7). Conclusion: For most patients, this multi-center study showed that ventilation waveforms were present in less than 50% of pauses in chest compressions during 30:2 CPR with BVM ventilation.