Bag-Valve-Mask Ventilation and Survival From Out-of-Hospital Cardiac Arrest: A Multicenter Study

Abstract

Background: Few studies have measured ventilation during early cardiopulmonary resuscitation (CPR) before advanced airway placement. Resuscitation guidelines recommend pauses after every 30 chest compressions to deliver ventilations. The effectiveness of bag-valve-mask ventilation delivered during the pause in chest compressions is unknown. We sought to determine: (1) the incidence of lung inflation with bag-valve-mask ventilation during 30:2 CPR; and (2) the association of ventilation with outcomes after out-of-hospital cardiac arrest.

Methods: We studied patients with out-of-hospital cardiac arrest from 6 sites of the Resuscitation Outcomes Consortium CCC study (Trial of Continuous Compressions versus Standard CPR in Patients with Out-of-Hospital Cardiac Arrest). We analyzed patients assigned to the 30:2 CPR arm with ≥2 minutes of thoracic bioimpedance signal recorded with a cardiac defibrillator/monitor. Detectable ventilation waveforms were defined as having a bioimpedance amplitude ≥0.5 Ω (corresponding to ≥250 mL V_T) and a duration ≥1 s. We defined a chest compression pause as a 3- to 15-s break in chest compressions. We compared the incidence of ventilation and outcomes in 2 groups: patients with ventilation waveforms in <50% of pauses (group 1) versus those with waveforms in ≥50% of pauses (group 2).

Results: Among 1976 patients, the mean age was 65 years; 66% were male. From the start of chest compressions until advanced airway placement, mean±SD duration of 30:2 CPR was 9.8±4.9 minutes. During this period, we identified 26 861 pauses in chest compressions; 60% of patients had ventilation waveforms in <50% of pauses (group 1, n=1177), and 40% had waveforms in ≥50% of pauses (group 2, n=799). Group 1 had a median of 12 pauses and 2 ventilations per patient versus group 2, which had 12 pauses and 12 ventilations per patient. Group 2 had higher rates of prehospital return of spontaneous circulation (40.7% versus 25.2%; P<0.0001), survival to hospital discharge (13.5% versus 4.1%; P<0.0001), and survival with favorable neurological outcome (10.6% versus 2.4%; P<0.0001). These associations persisted after adjustment for confounders.

Conclusions: In this study, lung inflation occurred infrequently with bag-valve-mask ventilation during 30:2 CPR. Lung inflation in ≥50% of pauses was associated with improved return of spontaneous circulation, survival, and survival with favorable neurological outcome.

Keywords: cardiography, impedance; cardiopulmonary resuscitation; heart arrest; patient outcome assessment; ventilation.

Figure 1.

CONSORT Diagram: Study cohort and exclusions. ROC indicates Resuscitation Outcomes Consortium; CCC, Trial of Continuous or Interrupted Chest Compressions during CPR; CPR, cardiopulmonary resuscitation; LP, Physio-Control/Stryker LIFEPAK defibrillator (models LP12 and LP15); MRx, Philips MRx defibrillator; 30:2 refers to cycles of 30 chest compressions to 2 ventilations during CPR.

Figure 2.

Ventilations per pause and outcomes. Association of the number of ventilations per pause vs. outcomes using natural cubic spline models (unadjusted and adjusted): (a, e) probability (prob) of return of spontaneous circulation (ROSC) on arrival at the emergency department (ED) vs. ventilations per pause (b, f) probability of hospital admission (admission) vs. ventilations per pause (c, g) probability of survival to hospital discharge vs. ventilations per pause (d, h) probability of mRS (modified Rankin Score) of 3 or less (favorable neurological outcome) vs. ventilations per pause. Figures e, f, g, and h were adjusted for age, sex, bystander-witnessed cardiac arrest, attempted bystander CPR, public location, first known EMS rhythm, and ROC site.

Figure 2.

Ventilations per pause and outcomes. Association of the number of ventilations per pause vs. outcomes using natural cubic spline models (unadjusted and adjusted): (a, e) probability (prob) of return of spontaneous circulation (ROSC) on arrival at the emergency department (ED) vs. ventilations per pause (b, f) probability of hospital admission (admission) vs. ventilations per pause (c, g) probability of survival to hospital discharge vs. ventilations per pause (d, h) probability of mRS (modified Rankin Score) of 3 or less (favorable neurological outcome) vs. ventilations per pause. Figures e, f, g, and h were adjusted for age, sex, bystander-witnessed cardiac arrest, attempted bystander CPR, public location, first known EMS rhythm, and ROC site.