PURPOSE OF THE STUDY.
Some argues that survival for OOHCA are poor if the RT are more than 12 (1) or 15 (2) minutes. We wanted to calculate survival for Paramedic-observed-arrest and at different RT-intervals in our EMS-system where median RT exceeds 10 minutes, but the bystander CPR-rate is relatively high.

MATERIALS AND METHODS
Register based study from Vestfold & Telemark 2007-15 (EMS-area 15.102 km², average population 369.000, 18 Ambulance-stations  with 1-4 vehicles). The Emergency Medical Communication Centre Tønsberg receives the medical emergency phone 113, and dispatches all vehicles. We used Chi2-tests for statistics. Incidence rate was calculated as patient numbers  per 100.000 residents per year.

RESULTS
The EMS attended 76.1 and  started or continued CPR in 60.9 patients per 100.000 person-year during the study period.   The RT for the first vehicle was not documented in 196 cases (Incidence 5,9). EMS were present and observed the arrest 334 times (Incidence 10.1) . The incidence of survival to day 30, (SD30) was 8.1
Maximal RT for SD30 were 37 minutes over all, and 30 minutes (3) for the “Utstein comparator group”.  The bystander CPR-rate rose from 46 % to 78 % during the study period. 


CONCLUSION
The SD30 was highest when the hypothetical RT was Zero (Paramedic observed arrest) The difference in SD30 between, paramedic observed, >0-<15 and 15-<30 minutes were both significant, but there were no significant difference in SD30 for RT >0<15 and 15-<30 minutes. Survival was possible at response times far beyond 15 minutes, as long as bystanders provided CPR until the EMS arrived.

REFERENCES
1) University of Washington School of Medicine. Survive Cardiac Arrest. [Online].; 2009 [cited 2018 Januar 4. Available from: https://depts.washington.edu/survive/survival-formula.php
2) Gold LS, Fahrenbruch CE, Rea TD, Eisenberg MS. The relationship between time to arrival of emergency medical services (EMS) and survival from out-of-hospital ventricular fibrillation cardiac arrest. Resuscitation. 2010;81(5):622-5  
3) Steen-Hansen JE. Favourable outcome after 26 minutes of "Compression only" resuscitation: a case report. Scand J Trauma Resusc Emerg Med. 2010: p. 19.

2 - Survival from Out-of-hospital-cardiac-arrest (OOHCA) at different Response time (RT) intervals