Introduction: this study explores why resuscitation is withheld when mobile emergency medical team arrive at the scene of a cardiac arrest.

Methods: we conducted a prospective, observational study in pre hospital emergency services. We included adults' patients, with a suspicion of non traumatic cardiac arrest (CA) in an out of hospital environment, who received or not cardiopulmonary resuscitation (CPR) by our mobile emergency medical service teams. An analytic study was conducted in order to identify independent factors that could influence the decision to resuscitate OHCA.

Results: during study, 228 patients were enrolled, the mean age was 64 +/- 14 years and 59% were men. Eighteen patients (8%) received bystander CPR by witnesses. The median time elapsed to arrive at the scene was 13 [8-25] min. The median "noflow" was 22 [10-34] min. The resuscitation decision was taken by the mobile EMS staff for 106 patients (46.5%). For other patients, the decision not to resuscitate was motivated solely by the finding of a confirmed state of death in an elderly patient (p = 0.045). The predictive decision factor for resuscitation was the no flow time less than 18.5 min, Odds Ratio adjusted with 95% confidence interval to: 1.38 (1.24 - 3.55) (p <0.001). Overall out of hospital survival rate was 17% of resuscitated patients.

Conclusion: the decision to resuscitate a cardiac arrest outside of the hospital depends more on the "no flow" time than on the presumed etiologies.