title: Optimal loop duration during the provision of in-hospital advanced life support (ALS) to patients with an initial non-shockable rhythm.
abstract: BACKGROUND
  In advanced life support (ALS), time-cycled "loops" of chest compressions form the basis of action. However, the provider must compromise between interrupting compressions and detecting a change in cardiac rhythm. An "optimal" loop duration would best balance these choices. The current international CPR guidelines recommend 2-min loop durations. The aim of this study was to investigate the "optimal" loop duration in patients with initial asystole or pulseless electrical activity (PEA).
  
  
  METHODS
  Detailed defibrillator recordings from 249 in-hospital cardiac arrests at the University of Chicago Medicine (Chicago, IL) and St. Olav University Hospital (Trondheim, Norway) were analysed. The clinical states of asystole, PEA, ventricular fibrillation/-tachycardia (VF/VT) and return of spontaneous circulation (ROSC) were annotated along the time axis. PEA and asystole were combined as a single state for the analysis of state development. The probability of staying in PEA/asystole over time was estimated non-parametrically. In addition, to distinguish between initial and secondary PEA/asystole, the latter was defined by the transition from VF/VT or ROSC.
  
  
  RESULTS
  Among patients with initial PEA (n=179), 25% and 50% of patients had left PEA/asystole after 4 and 9 min of ALS efforts, respectively. The corresponding time points for patients with initial asystole (n=70) were 7.3 and 13.3 min, respectively. The probability of transition from secondary PEA/asystole to ROSC or VF/VT varied between 10% and 20% in each 2-4 min interval.
  
  
  CONCLUSIONS
  The "optimal" first loop duration may be 4 min in initial PEA and 6-8 min in initial asystole. If secondary PEA/asystole is encountered, 2-min loop duration seems appropriate.
authors.affiliation: Department of Circulation and Medical Imaging, Faculty of Medicine, Norwegian University of Science and Technology, NO-7491 Trondheim, Norway; The Norwegian Air Ambulance Foundation, NO-1441 Drøbak, Norway; St. Olav University Hospital, NO-7006 Trondheim, Norway. Electronic address: trond.nordseth@ntnu.no.
authors.forename: Trond
authors.initials: T
authors.lastname: Nordseth
authors.affiliation: University of Chicago Medicine, 5841 South Maryland Avenue, Chicago, IL 60637, USA.
authors.forename: Dana Peres
authors.initials: DP
authors.lastname: Edelson
authors.affiliation: Department of Circulation and Medical Imaging, Faculty of Medicine, Norwegian University of Science and Technology, NO-7491 Trondheim, Norway; The Norwegian Air Ambulance Foundation, NO-1441 Drøbak, Norway; St. Olav University Hospital, NO-7006 Trondheim, Norway.
authors.forename: Daniel
authors.initials: D
authors.lastname: Bergum
authors.affiliation: Division of Critical Care, Oslo University Hospital, PB 4956 Nydalen, NO 0424 Oslo, Norway.
authors.forename: Theresa Mariero
authors.initials: TM
authors.lastname: Olasveengen
authors.affiliation: Department of Electrical Engineering and Computer Science, Faculty of Science and Technology, University of Stavanger, N-4036 Stavanger, Norway.
authors.forename: Trygve
authors.initials: T
authors.lastname: Eftestøl
authors.affiliation: Department of Circulation and Medical Imaging, Faculty of Medicine, Norwegian University of Science and Technology, NO-7491 Trondheim, Norway; St. Olav University Hospital, NO-7006 Trondheim, Norway.
authors.forename: Rune
authors.initials: R
authors.lastname: Wiseth
authors.affiliation: Department of Mathematics and Natural Sciences, Faculty of Science and Technology, University of Stavanger, N-4036 Stavanger, Norway.
authors.forename: Jan Terje
authors.initials: JT
authors.lastname: Kvaløy
authors.affiliation: Center for Resuscitation Science, Department of Emergency Medicine, University of Pennsylvania, 3400 Spruce Street, Philadelphia, PA 19104, USA.
authors.forename: Benjamin S
authors.initials: BS
authors.lastname: Abella
authors.affiliation: Department of Circulation and Medical Imaging, Faculty of Medicine, Norwegian University of Science and Technology, NO-7491 Trondheim, Norway; The Norwegian Air Ambulance Foundation, NO-1441 Drøbak, Norway; St. Olav University Hospital, NO-7006 Trondheim, Norway.
authors.forename: Eirik
authors.initials: E
authors.lastname: Skogvoll
mesh_terms: D022561:Advanced Cardiac Life Support / Q000379:methods*; D000368:Aged; D005260:Female; D006323:Heart Arrest / Q000503:physiopathology* / Q000628:therapy; D006760:Hospitalization; D006801:Humans; D008297:Male; D008875:Middle Aged; D013997:Time Factors
keywords: Cardiac arrest; Cardiopulmonary resuscitation; Dynamics