Compression Only CPR Versus Standard CPR in Out-Of-Hospital Cardiac Arrest - A Randomized Survival Study (TANGO2)

A Randomized Trial Comparing Survival After of a Simplified Form of Cardiopulmonary Resuscitation (CPR) Consisting of Compressions Only Compared to CPR With Compressions and Rescue Breaths

Out-of-hospital cardiac arrest (OHCA) is one of the leading causes of mortality in the industrialized world. Bystander CPR before arrival of the Emergency Medical Service (EMS) is associated with an increased chance of survival.

During the last decade, the best form of bystander CPR has been debated. Chest Compression Only CPR (CO-CPR) has been advocated as a preferable method in situations where the bystander has no previous knowledge in CPR, both because its believed to be equally efficient but also a simplified form of CPR that could lead to a higher incidence of bystander-CPR.

In an initiative to increase CPR rates the American Heart Association has launched public campaigns such as the "hands-only CPR" promoting CO-CPR as an option to S-CPR for adult non-asphyxic cardiac arrest. In the 2015 updates of the European resuscitation council guidelines it states that the confidence in the equivalence between the two methods is not sufficient to change current practice.

Whether CO-CPR leads to a survival rate no worse than, or even superior to standard CPR in situations where the bystander has previous CPR training remains unclear. This clinical question remains unanswered while millions of people are trained in CPR worldwide each year.

To investigate whether CO-CPR is non-inferior to standard CPR (S-CPR) when performed by a bystander with previous CPR training in witnessed, non-asphyxic cases of OHCA. Superiority testing will also be performed for the purpose of demonstrating a possible increase in survival with CO-CPR.

Study Overview

• Status: Recruiting
• Conditions: Cardiac Arrest; Cardiopulmonary Resuscitation; Out-Of-Hospital Cardiac Arrest
• Intervention / Treatment: Other: Chest Compression Only CPR (CO-CPR) performed by trained bystanders after instructions from dispatchers; Other: Standard CPR (S-CPR) performed by trained bystanders after instructions from dispatchers

Detailed Description

This is an interventional, prospective, randomized, 1:1 open label, multicenter trial comparing two different methods of bystander CPR in witnessed cases of OHCA. Since CO-CPR is a simplified form of CPR that could lead to a higher rate of bystander-CPR by itself, a non-inferiority design for the primary outcome has been chosen. Superiority testing will also be performed to demonstrate a potential increase in survival with CO-CPR.

Witnessed cases of OHCA with a non-asphyctic aetiology will be the principal study population. According to current guidelines, an unresponsive patient with no or agonal breathing is treated as a suspected case of OHCA at the dispatch centre. These cases are eligible for screening for inclusion. If the case is witnessed, the bystander has previous knowledge in CPR, and no exclusion criteria are present, the case can be included in the study. If included, it will be randomly assigned to either CO-CPR (intervention) or S-CPR (control).

The intervention consists of instructions from a dispatcher at the dispatch center to bystanders to perform either CO-CPR (intervention) or S-CPR (control).

• Instructions to bystanders on how to perform CO-CPR include continuous chest compressions without interruptions or rescue breaths.
• Instructions to bystanders on how to perform S-CPR in the control group include information on giving chest compressions and rescue breaths in a 30:2 ratio.

This is a national study where all dispatch centers in Sweden participate, and since 2025, selected sites in northern Italy.

The overall study project is conducted in three different phases:

1. RUN-IN period, for establishing logistical and technical study procedures (completed)
2. PILOT STUDY, with focus on feasibility, logistics, and safety (completed)
3. MAIN STUDY will focus on 30-day survival (primary end point) and other important clinical outcomes (secondary outcomes)

Objective for RUN-IN period:

In order to test the technical inclusion procedures, logistics, feasibility, and data collection, a pre-study RUN-IN period started in Stockholm during 2015.

Objective PILOT study:

The PILOT study aimed to assess the safety and feasibility of the TANGO2 trial design, as well as intermediate clinical outcomes. The TANGO2 trial started recruitment of patients on January 1st, 2017, and the last patient was included on December 31st, 2018. All patients from the PILOT study will be included in the MAIN STUDY in a seamless design.

Objective MAIN study:

The MAIN study aims to evaluate whether survival to 30 days following instructions to perform CO-CPR is non-inferior to instructions to perform S-CPR in witnessed OHCA where the bystander has previous CPR training.

• Study Type: Interventional
• Enrollment (Estimated): 3260
• Phase: Not Applicable

Contacts and Locations

• Study Contact: Name: Jacob Hollenberg, MD. PhD; Phone Number: 004686163816; Email: jacob.hollenberg@ki.se

Study Locations

• Italy
  • Bergamo, Italy
    • Recruiting
    • AREU, Agenzia Regionale Emergenza Urgenza
• Sweden
  • Stockholm, Sweden
    • Recruiting
    • SOS Alarm AB

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: 18 years and older (Adult, Older Adult)
• Accepts Healthy Volunteers: No

Description

Inclusion Criteria:

• Unconsciousness with no, abnormal or agonal breathing (suspected OHCA)
• The suspected OHCA is witnessed (seen or heard)
• Any Bystander at the scene has previous training in CPR

Exclusion Criteria:

• Age below 18 years
• Collapse is not witnessed
• Bystander has no prior CPR training
• Obvious asphyxia (i.e. hanging, foreign body, suffocation, strangulation)
• Obvious drug overdose / intoxication
• Pregnancy
• Trauma (penetrating, blunt, burn injury)

Post randomisation exclusion Criteria from data analysis:

• Not EMS-verified cardiac arrest
• Previous do not resuscitate (DNR) decision

Study Plan

How is the study designed?

Design Details

• Primary Purpose: Treatment
• Allocation: Randomized
• Interventional Model: Parallel Assignment
• Masking: Double

Number of Arms

2

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
Experimental: Chest Compression Only CPR (CO-CPR); Instructions from a dispatcher at the dispatch center to trained bystanders to perform CO-CPR with chest compressions only.	Other: Chest Compression Only CPR (CO-CPR) performed by trained bystanders after instructions from dispatchers; Instructions by dispatcher to bystander to provide CPR with chest-compressions only The instructions from the dispatcher in interventional arm include: An ambulance is dispatched and is on it´s way to you; Do CPR with chest compressions only; Push hard on the chest with a pace of 100/minute without interruptions for rescue breathing.; Other Names: Compression only CPR; Chest compression only CPR; Hands-only CPR
Active Comparator: Standard CPR (S-CPR); Instructions from a dispatcher at the dispatch center to trained bystanders to perform S-CPR with chest compressions and rescue breaths in a 30:2 ratio.	Other: Standard CPR (S-CPR) performed by trained bystanders after instructions from dispatchers; Instructions by dispatcher to bystander to provide CPR with chest-compressions and rescue breaths in a ration of 30:2 The Instructions from the dispatcher in the control arm include: An ambulance is dispatched and is on it´s way to you; Do CPR with chest compressions and rescue breathing; Push hard on the chest 30 times and give 2 rescue breaths. The pace of the compressions should be 100/minute.; Other Names: Standard CPR

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
30-day survival	Survival to 30 days after cardiac arrest	1 month

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Survival with good neurologic outcome at discharge	Survival to hospital discharge with cerebral performance category (CPC) 1-2	30 days
1-day survival	1-day survival will be derived from the date of death recorded in Swedish Cardiopulmonary Resuscitation Registry (SRCR). Because SRCR only provides the calendar date of death (and not the exact time), we cannot reliably determine the Utstein variable "survival to hospital admission". We therefore will use 1-day survival as a proxy. If the SRCR date of death is the calendar day after the event date, the patient will be classified as still alive after 1-day. Separating survival to hospital admission from early in-hospital death will not be possible with the available SRCR data.	1 day
1-year survival	Survival to 1-year after cardiac arrest	1 year

Other Outcome Measures

Outcome Measure	Measure Description	Time Frame
Proportion of participants with return of spontaneous Circulation (ROSC)	Proportion of participants with return of spontaneous Circulation	1 day
Proportion of participants found with VT/VF at first rhythm analysis	Proportion of participants found with ventricular tachycardia (VT) or ventricular fibrillation (VF) at first rhythm analysis by the EMS or by an automated external defibrillator (AED)	1 day
Analysis of primary endpoint (30-day survival) in pre-defined subgroup	Subgroups will be analysed according to the following pre-defined variables: Sex, Age, Cause of OHCA, Initial rhythm, Location of cardiac arrest, Time to start of bystadner CPR, Time to arrival of EMS and Neurological severity classification (CPC).	30 days

Collaborators and Investigators

• Sponsor: Karolinska Institutet
• Collaborators: The Swedish Research Council; Swedish Heart Lung Foundation; SOS Alarm; Azienda Regionale Emergenza Urgenza - AREU Lombardia
• Investigators: Principal Investigator: Jacob Hollenberg, MD, PhD, Karolinska Institutet; Study Chair: Andreas Claesson, RN, PhD, Karolinska Institutet; Study Chair: Giuseppe Ristagno, MD, PhD, University of Milan; Study Chair: Gabril Riva, MD, PhD, Karolinska Institutet; Study Chair: Martin Jonsson, McS, PhD, Karolinska Institutet; Study Chair: Mattias Ringh, MD, PhD, Karolinska Institutet; Study Chair: Per Nordberg, MD, PhD, Karolinska Institutet; Study Chair: Annette Nord, RN, PhD, Karolinska Institutet; Study Chair: Marcus Skrifvars, MD, PhD, University of Helsinki

Study record dates

Study Major Dates

• Study Start (Actual): January 1, 2017
• Primary Completion (Estimated): December 31, 2027
• Study Completion (Estimated): December 31, 2028

Study Registration Dates

• First Submitted: June 5, 2019
• First Submitted That Met QC Criteria: June 7, 2019
• First Posted (Actual): June 10, 2019

Study Record Updates

• Last Update Posted (Actual): May 8, 2026
• Last Update Submitted That Met QC Criteria: May 4, 2026
• Last Verified: May 1, 2026

More Information

Terms related to this study

• Keywords: Cardiac Arrest; Cardiopulmonary Resuscitation; Chest compressions only CPR; Dispatcher assisted CPR
• Additional Relevant MeSH Terms: Cardiovascular Diseases; Heart Diseases; Heart Arrest; Out-of-Hospital Cardiac Arrest
• Other Study ID Numbers: NCT3

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: NO
• IPD Plan Description: Data will be published on group level only

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: No
• Studies a U.S. FDA-regulated device product: No