Continuous vs Interrupted Chest Compressions During CPR
The study: Do continuous chest compressions with asynchronous ventilation, as compared to chest compressions interrupted for ventilation, during CPR performed by EMS providers affect the rate of survival, neurologic function or the rate of adverse events?
Included 114 different EMS agencies grouped into 47 clusters. Clusters were randomly assigned to perform either continuous compression or interrupted compression during all out of hospital cardiac arrests, then switched twice per year (4 year study).
Patients had to be adults with non trauma related out of hospital cardiac arrest who received compressions performed by providers from participating EMS agencies.
Exclusions: EMS witnessed arrest, DNR, trauma/uncontrolled bleeding, trach, prisoners, initial CPR performed by nonparticipating EMS provider (but bystander ok), mechanical chest compression device, advance airway before arrival
Chest compression specifics:
Continuous: 100 compressions/min with asynchronous positive pressure ventilation delivered at 10 ventilations per minute
Interrupted: 30:2 ratio with ventilations given during less than 5 seconds
Ventilations were mostly with BVM but could be any positive pressure ventilation. There were no specific requirements for ventilation.
Primary: survival to hospital discharge
Secondary: neurologic function at discharge by mRS (0 = fine, 6 = dead), adverse events, hospital free survival (number of days alive/out of hospital in first 30 days)
12,613 patients in intervention group (continuous) and 1129 (9.0%) survived
11,035 patients in control group and 1072 (9.7%) survived
not a significant difference (P = 0.07)
883 of 12,560 patients (7.0%) in intervention group had mRS < 3 at discharge
844 of 10,995 patients (7.7%) in control group had mRS < 3 at discharge
not significant difference (P = 0.09)
Intervention patients were significantly less likely to be transported to the hospital or admitted to the hospital
Hospital free survival was significantly shorter in the intervention group
Per-protocol population (removed many patients due to imbalances such as shockable rhythm): survival rate significantly lower in the intervention group (6529 patients) than the control group (3678 patients)
No differences in adverse events
Measured but did not control/adjust for postresuscitation care so patients could have received varying care after their initial EMS encounter.
No control or mention whatsoever of specifics of ventilations.
In an attempt to be broadly applicable this study used many different EMS agencies from all over the country but did not control anything other than compression/ventilation so other aspects of the medical code protocol could have been very different.
In patients with out of hospital cardiac arrest, continuous compressions did not result in significantly higher rates of survival or favorable neurologic outcomes than did interrupted chest compressions. However this study was limited by a lack of control of post cardiac arrest care, no specifications for ventilations and many other uncontrolled variables. This is an example of how trying to make a study too broad and too generally applicable can make it not able to really say anything.
Key point: This was a relatively poorly designed study. It’s not practice changing but important to note that the interrupted chest compressions group had ventilations delivered over less than 5 seconds and the authors point out that the mean difference in chest compression fraction (proportion of each minute during which compressions were given) between the two groups was small (0.83 in the intervention group and 0.77 in the control group). Bottom line is minimize interruptions in chest compressions (but you already knew that).
Nichol G, et al. Trial of Continuous or Interrupted Chest Compressions during CPR. New England Journal of Medicine 2015;373:2203-14.