NCT02401633.

Trial name or title	A randomized trial comparing the effect of a simplified form of cardiopulmonary resuscitation (CPR) consisting of only chest compressions compared to CPR with compressions and rescue breaths ‐ the run‐in phase
Methods	Randomized controlled trial
Participants	Inclusion criteria: Unconsciousness with no abnormal or agonal breathing (suspected OHCA) The suspected OHCA is witnessed (seen or heard), bystander has previous training in CPR Exclusion Criteria: Age 18 or younger Collapse is not witnessed Bystander has never been trained in CPR (these bystanders should be instructed to administer CO‐CPR in accordance with guidelines) Obvious asphyxia, i.e. drowning, strangulation, hanging Obvious intoxication or drug overdose Obvious pregnancy Trauma Bystander is unwilling to participate or to perform CPR
Interventions	Intervention group: CPR provided by bystander with chest compressions only Control group: Instructions by dispatcher to bystander to provide CPR with chest compressions and rescue breaths in a 30:2 ratio
Outcomes	Unknown
Starting date	February 2015
Contact information	Contact: Jacob Hollenberg, MD, PhD, +46704133442, jacob.hollenberg@ki.se Contact: Gabriel Riva, MD, +46705452086, gabriel.riva@ki.se
Notes

CO‐CPR: Chest compression‐only cardiopulmonary resuscitation; CPR: cardiopulmonary resuscitation; OHCA: out‐of‐hospital cardiac arrest.