title: The response time threshold for predicting favourable neurological outcomes in patients with bystander-witnessed out-of-hospital cardiac arrest.
abstract: It is well established that the period of time between a call being made to emergency medical services (EMS) and the time at which the EMS arrive at the scene (i.e. the response time) affects survival outcomes in patients who experience out-of-hospital cardiac arrest (OHCA). However, the relationship between the response time and favourable neurological outcomes remains unclear. We therefore aimed to determine a response time threshold in patients with bystander-witnessed OHCA that is associated with positive neurological outcomes and to assess the relationship between the response time and neurological outcomes in patients with OHCA.
  
  
  
  This study was a retrospective, observational analysis of data from 204,277 episodes of bystander-witnessed OHCA between 2006 and 2012 in Japan. We used classification and regression trees (CARTs) and receiver operating characteristic (ROC) curve analyses to determine the threshold of response time associated with favourable neurological outcomes (Cerebral Performance Category 1 or 2) 1 month after cardiac arrest.
  
  
  
  Both CARTs and ROC analyses indicated that a threshold of 6.5min was associated with improved neurological outcomes in all bystander-witnessed OHCA events of cardiac origin. Furthermore, bystander cardiopulmonary resuscitation (CPR) prolonged the threshold of response time by 1min (up to 7.5min). The adjusted odds ratio for favourable neurological outcomes in patients with OHCA who received care within ≤6.5min was 1.935 (95% confidential interval: 1.834-2.041, P<0.001).
  
  
  
  A response time of ≤6.5min was closely associated with favourable neurological outcomes in all bystander-witnessed patients with OHCA. Bystander CPR prolonged the response time threshold by 1min.
authors.affiliation: Division of Acute and Critical Care Medicine, Department of Anesthesiology and Critical Care Medicine, Hokkaido University Graduate School of Medicine, Sapporo, Hokkaido, Japan. Electronic address: rjtkk3299@yahoo.co.jp.
authors.forename: Yuichi
authors.initials: Y
authors.lastname: Ono
authors.affiliation: Division of Acute and Critical Care Medicine, Department of Anesthesiology and Critical Care Medicine, Hokkaido University Graduate School of Medicine, Sapporo, Hokkaido, Japan.
authors.forename: Mineji
authors.initials: M
authors.lastname: Hayakawa
authors.affiliation: Division of Clinical Research and Medical Innovation Center, Hokkaido University Hospital, Sapporo, Hokkaido, Japan.
authors.forename: Hiroaki
authors.initials: H
authors.lastname: Iijima
authors.affiliation: Division of Acute and Critical Care Medicine, Department of Anesthesiology and Critical Care Medicine, Hokkaido University Graduate School of Medicine, Sapporo, Hokkaido, Japan.
authors.forename: Kunihiko
authors.initials: K
authors.lastname: Maekawa
authors.affiliation: Division of Acute and Critical Care Medicine, Department of Anesthesiology and Critical Care Medicine, Hokkaido University Graduate School of Medicine, Sapporo, Hokkaido, Japan.
authors.forename: Akira
authors.initials: A
authors.lastname: Kodate
authors.affiliation: Division of Acute and Critical Care Medicine, Department of Anesthesiology and Critical Care Medicine, Hokkaido University Graduate School of Medicine, Sapporo, Hokkaido, Japan.
authors.forename: Yoshihiro
authors.initials: Y
authors.lastname: Sadamoto
authors.affiliation: Division of Acute and Critical Care Medicine, Department of Anesthesiology and Critical Care Medicine, Hokkaido University Graduate School of Medicine, Sapporo, Hokkaido, Japan.
authors.forename: Asumi
authors.initials: A
authors.lastname: Mizugaki
authors.affiliation: Division of Acute and Critical Care Medicine, Department of Anesthesiology and Critical Care Medicine, Hokkaido University Graduate School of Medicine, Sapporo, Hokkaido, Japan.
authors.forename: Hiromoto
authors.initials: H
authors.lastname: Murakami
authors.affiliation: Division of Acute and Critical Care Medicine, Department of Anesthesiology and Critical Care Medicine, Hokkaido University Graduate School of Medicine, Sapporo, Hokkaido, Japan.
authors.forename: Kenichi
authors.initials: K
authors.lastname: Katabami
authors.affiliation: Division of Acute and Critical Care Medicine, Department of Anesthesiology and Critical Care Medicine, Hokkaido University Graduate School of Medicine, Sapporo, Hokkaido, Japan.
authors.forename: Atsushi
authors.initials: A
authors.lastname: Sawamura
authors.affiliation: Division of Acute and Critical Care Medicine, Department of Anesthesiology and Critical Care Medicine, Hokkaido University Graduate School of Medicine, Sapporo, Hokkaido, Japan.
authors.forename: Satoshi
authors.initials: S
authors.lastname: Gando
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D016887:Cardiopulmonary Resuscitation / Q000009:adverse effects / Q000379:methods; D004632:Emergency Medical Services / Q000592:standards / Q000706:statistics & numerical data; D005260:Female; D005392:First Aid / Q000009:adverse effects / Q000592:standards / Q000706:statistics & numerical data; D006331:Heart Diseases / Q000150:complications*; D006801:Humans; D007564:Japan / Q000453:epidemiology; D008297:Male; D009422:Nervous System Diseases / Q000453:epidemiology / Q000209:etiology; D058687:Out-of-Hospital Cardiac Arrest / Q000453:epidemiology / Q000209:etiology / Q000628:therapy; D010043:Outcome and Process Assessment, Health Care; D011379:Prognosis; D012189:Retrospective Studies; D061665:Time-to-Treatment / Q000592:standards / Q000706:statistics & numerical data
keywords: Neurological outcome; Out of hospital cardiac arrest; Response time