Paramedic Out-of-Hospital Cardiac Arrest Case Volume Is a Predictor of Return of Spontaneous Circulation

Jenna E. Tuttle, MHS, NRP; Michael W. Hubble, PhD, NRP


Western J Emerg Med. 2018;19(4):654-659. 

In This Article


During the study period, 8,790 patients met inclusionary criteria. Of these, 2,385 were excluded due to incomplete data elements. Of the 6,405 patients included in the analysis, the mean age was 66.5 (±15.2) years and males accounted for 61.7% of the sample. A shockable rhythm was the first presenting rhythm upon EMS arrival in 30.0% of cases. The mean EMS response time, measured as call receipt to scene arrival, was 8.3 (±4.8) minutes, and layperson/first responder CPR was performed prior to EMS arrival in 44.0% of cases. In total, 3,155 patients (49.3%) experienced ROSC. The lead paramedics attending the patients in the database had participated in an average of 23.6 (±20.3) OHCA cases in the previous five years, either as the "code leader" or in a secondary role. Additional details of the sample are provided in Table 1.

The results of the univariate analysis of ROSC are presented in Table 2. Notably, compared to patients without ROSC, a greater proportion of patients with ROSC received layperson/first responder CPR (60.0% vs. 51.4%, p = 0.03) and presented with a shockable rhythm (38.9 vs. 21.2%, p < 0.01), but were less likely to be male (60.1% vs. 63.2%, p < 0.01). Patients with ROSC also had shorter EMS response times (7.7 vs. 8.9 minutes, p < 0.01) and were treated by paramedics with greater five-year cumulative OHCA experience (24.5 vs. 22.7, p<0.01).

We used logistic regression to control for potentially confounding variables. Based on clinical reasoning, the following variables were entered into the model: paramedic OHCA experience ≥15 in the previous five years; patient age, gender, and non-Caucasian race; shockable presenting rhythm; layperson/first responder CPR; and EMS response time. OHCA case volume was defined as a binary variable of participation in ≥ 15 previous resuscitation attempts. This level of case volume was selected because the probability of ROSC by OHCA case volume appeared to plateau around 15 previous arrests (Figure).


Percentage return of spontaneous circulation (ROSC) by paramedic cumulative out-of-hospital cardiac arrest (OHCA) cumulative case volume. Proportion of patients attaining ROSC by paramedic five-year OHCA case volume.

ROSC was more likely when the patient was treated by a lead paramedic who had attended 15 or more cardiac arrests in the previous year (OR [1.21], p<0.01), and less likely with increasing age (OR [0.99], p <0.02) and EMS response time (OR [0.95], p<0.01). Compared to patients with non-shockable rhythms, patients with shockable rhythms were more likely to achieve ROSC (OR [2.35], p<0.01). ROSC was more likely among patients receiving layperson/first responder CPR (OR [1.77], p<0.01) and less likely among males (OR [0.74], p<0.01). Non-Caucasian race was not an independent predictor of ROSC. Details on the logistic regression results for ROSC are provided in Table 3.

With the exception of scene arrival to administration of the first vasopressor time interval, there were no differences in the time required to perform on-scene skills between paramedics with and without 15 or more cumulative OHCA experiences (Table 4).