Abstract Body: Background: The two-minute interval between rhythm analyses has long been the standard in resuscitation, primarily due to its simplicity and ease of application. However, there is no definitive evidence that two minutes represents the optimal interval for all cases.
Aims: To estimate the chest compression fraction (CCF) and ventricular fibrillation (VF) duration associated with basic life support guidelines (ERC/AHA) over years for shockable and non-shockable rhythms.
Methods: An analysis/CPR cycle refers to the smallest repeating sequence of events during resuscitation, including rhythm analysis, pulse check, shock delivery, ventilation, and chest compressions (CC). The structure and timing of these cycles vary depending on the resuscitation guidelines in effect at different times. Fixed durations were assigned to each event to enable comparison across guidelines (see Table). CCF is defined as the proportion of the cycle during which CC are delivered. VF duration refers to the time a patient remains in ventricular fibrillation during a cycle, beginning at refibrillation and ending with a successful shock. Time to refibrillation was set at 1 minute, based on observations that most of refibrillations occur within the first minute after a shock.
Results: The timeline of guideline updates and estimates of CCF and VF duration are summarized in Figure 1A and 1B. For shockable rhythms, estimated VF duration ranged from 11 to 41 seconds under the 1998 and 2000 guidelines, due to stacked shocks. This duration increased to 67 seconds with the implementation of the 2-minute CPR in 2005, and to 72 seconds with the introduction of a higher compression rate in 2010. For non-shockable rhythms, estimated CCF was 59% under the 1998 guidelines with a 3-minute 15:2 CPR and dropped to 51% in 2000 with the change to 1-minute CPR. It increased to 72% in 2005 with the adoption of 2-minute CPR and 30:2 ratio, and slightly decreased to 69% in 2010 with the higher compression rate.
Conclusion: Shorter analysis/CPR cycles reduce VF duration by decreasing the interval between shocks, whereas longer cycles enhance CCF by minimizing CPR interruptions for rhythm analysis. The current 2-minute cycle improves CCF but prolongs VF duration compared to the previous 1-minute cycle. Future personalized guidelines could be expected to optimize both VF duration and CCF.