Out-Of-Hospital Cardiac ArrestTANGO2NCT03981107
Compression Only CPR Versus Standard CPR in Out-Of-Hospital Cardiac Arrest - A Randomized Survival Study
A study testing Chest Compression Only CPR (CO-CPR) performed by trained bystanders after instructions from dispatchers and Standard CPR (S-CPR) performed by trained bystanders after instructions from dispatchers in people with Out-Of-Hospital Cardiac Arrest and Cardiac Arrest, run by Karolinska Institutet at 2 sites in 2 countries.
Trial summary
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. Read more about this study
- Who is it for?
- Ages 18 years and older
- Conditions the study is for
- Out-Of-Hospital Cardiac Arrest, Cardiac Arrest, Cardiopulmonary Resuscitation
- What is being tested?
- Chest Compression Only CPR (CO-CPR) performed by trained bystanders after instructions from dispatchers and Standard CPR (S-CPR) performed by trained bystanders after instructions from dispatchers
- Could I receive a placebo?
- No, everyone receives an active treatment
- How many people
- 3,260 participants
- Where
- 2 sitesin 2 countries
- Study dates
- 1 Jan 2017to 31 Dec 2028
- Phase
- Interventional
- Are there results?
- Not yet: the study is under way
Key requirements
Who can take part, as listed by the sponsor. Only the study team can confirm whether you are eligible, so take this list to your doctor.
- Ages 18 years and older
- All sexes
- No healthy volunteers
- Adult, Older adult
Who may be able to join
- 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
Who cannot join
- 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
Show all 10Show fewer
- Trauma (penetrating, blunt, burn injury)
- Post randomisation exclusion Criteria from data analysis:
- Not EMS-verified cardiac arrest
- Previous do not resuscitate (DNR) decision
Trial locations and contacts
2 sites in 2 countries. Contact the study team or a site near you to ask about taking part.
2 sites in 2 countries
Italy1 site, 1 recruiting
- Recruiting
AREU, Agenzia Regionale Emergenza Urgenza
Bergamo
About this study
Official title: 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.
Read more
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.
Read the 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:
- RUN-IN period, for establishing logistical and technical study procedures (completed)
- PILOT STUDY, with focus on feasibility, logistics, and safety (completed)
- 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.
- Being tested
- Chest Compression Only CPR (CO-CPR) performed by trained bystanders after instructions from dispatchers, Standard CPR (S-CPR) performed by trained bystanders after instructions from dispatchers
- Keywords
- Cardiopulmonary Resuscitation, Chest compressions only CPR, Dispatcher assisted CPR, Cardiac Arrest
- Medical subject headings
- Out-of-Hospital Cardiac Arrest, Heart Arrest
What participants receive
What participants receive. In a randomised study each person is assigned to one group by chance.
Chest Compression Only CPR (CO-CPR) performed by trained bystanders after instructions from dispatchersOther
Also called Chest compression only CPR, Compression only CPR, Hands-only CPR
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.
Standard CPR (S-CPR) performed by trained bystanders after instructions from dispatchersOther
Also called Standard CPR
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.
| Study group | Role | What they receive |
|---|---|---|
| Chest Compression Only CPR (CO-CPR) | Experimental | Instructions from a dispatcher at the dispatch center to trained bystanders to perform CO-CPR with chest compressions only. Receives: Other: Chest Compression Only CPR (CO-CPR) performed by trained bystanders after instructions from dispatchers |
| Standard CPR (S-CPR) | Active comparator | 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. Receives: Other: Standard CPR (S-CPR) performed by trained bystanders after instructions from dispatchers |
What is being measured
The primary outcome is the main question the study is designed to answer.
30-day survival
Survival to 30 days after cardiac arrest
Measured: 1 month
Secondary outcomes (3)
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.
Measured: 1 day
1-year survival
Survival to 1-year after cardiac arrest
Measured: 1 year
Survival with good neurologic outcome at discharge
Survival to hospital discharge with cerebral performance category (CPC) 1-2
Measured: 30 days
Timeline
From the start of the study to its completion; the mark is today. Estimated dates are the sponsor’s plan.
- First posted10 Jun 2019
- Study start1 Jan 2017
- Primary completion31 Dec 2027 (estimated)
- Study completion31 Dec 2028 (estimated)
Resources
- Official record on ClinicalTrials.govThe registry entry this page is built from, with its full change history.
- Publications (1)Papers the sponsor has linked to this study.
- Other trials for Out-Of-Hospital Cardiac ArrestStudies of the same condition, open and under way.
- More trials run by Karolinska InstitutetThe sponsor's other registered studies.
- What the trial phases meanHow a treatment moves from first tests in people to approval.
More details
For doctors and researchers: how the study is designed, who runs it, and its registry IDs.
Study design
- Study type
- Interventional
- Phase
- Phase N/A
- Primary purpose
- Treatment
- Allocation
- Randomised
- Intervention model
- Parallel groups
- Model description
- Randomized, 1:1, open-label, multicenter trial
- Masking
- Double blind
- Who is masked
- Investigator, Outcomes assessor
- Enrolment
- 3,260 participants (estimated)
Sponsor and investigators
- Lead sponsor
- Karolinska Institutet
- Sponsor type
- University, hospital or other
- Collaborators
- Swedish Heart Lung Foundation, SOS Alarm, Azienda Regionale Emergenza Urgenza - AREU Lombardia, The Swedish Research Council
- Responsible party
- Principal investigator, Jacob Hollenberg, Karolinska Institutet
- Investigators
- Jacob Hollenberg, MD, PhD, Principal investigator, Karolinska InstitutetGiuseppe Ristagno, MD, PhD, Study chair, University of MilanGabril Riva, MD, PhD, Study chair, Karolinska InstitutetMartin Jonsson, McS, PhD, Study chair, Karolinska InstitutetMattias Ringh, MD, PhD, Study chair, Karolinska InstitutetPer Nordberg, MD, PhD, Study chair, Karolinska InstitutetAnnette Nord, RN, PhD, Study chair, Karolinska InstitutetAndreas Claesson, RN, PhD, Study chair, Karolinska Institutet
IDs, dates and publications
- ClinicalTrials.gov ID
- NCT03981107
- Sponsor's protocol ID
- NCT3
- Acronym
- TANGO2
- Status last verified
- May 2026
- First submitted
- 5 Jun 2019
- Last updated
- 8 May 2026
- Results posted
- No
- Data monitoring committee
- Yes
- FDA-regulated drug
- No
- FDA-regulated device
- No
- Individual data sharing
- No: Data will be published on group level only
Publications
Boberg E, Merigo G, Riva G, Ringh M, Ristagno G, Jonsson M, Nordius C, Magliocca A, Skrifvars MB, Byrsell F, Jonsson F, Claesson A, Svensson L, Nordberg P, Nord A, Hollenberg J. Design and rationale of the TANGO2 trial: A randomized controlled non-inferiority trial of bystander compression-only CPR versus standard CPR in out-of-hospital cardiac arrest. Am Heart J. 2026 Oct 6:107623. doi: 10.1016/j.ahj.2026.107623. Online ahead of print.
PubMed 42838476
Study at a glance
From the registry record, last updated by the sponsor on 8 May 2026. Recruitment status is as the sponsor reported it: confirm with the study team.
- Official title
- 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
- ClinicalTrials.gov ID
- NCT03981107
- Acronym / sponsor ID
- TANGO2 / NCT3
- Keywords
- Cardiopulmonary Resuscitation, Chest compressions only CPR, Dispatcher assisted CPR, Cardiac Arrest
- Study type
- Interventional
- Recruitment status
- Recruiting
- Enrolment
- 3,260 participants (estimated)
- Lead sponsor
- Karolinska InstitutetUniversity, hospital or other
- Collaborators
- Swedish Heart Lung Foundation, SOS Alarm, Azienda Regionale Emergenza Urgenza - AREU Lombardia, The Swedish Research Council
- Study start
- 1 Jan 2017 (actual)
- Primary completion
- 31 Dec 2027 (estimated)
- Study completion
- 31 Dec 2028 (estimated)
- First posted
- 10 Jun 2019 (actual)
- Results
- Not posted in the source record
Clinical summary
The research question as the sponsor registered it. This describes what the study plans to test, not what it found.
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.
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:
- RUN-IN period, for establishing logistical and technical study procedures (completed)
- PILOT STUDY, with focus on feasibility, logistics, and safety (completed)
- 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 design
- Primary purpose
- Treatment
- Allocation
- Randomised
- Intervention model
- Parallel groups
- Masking
- Double blind (investigator, outcomes assessor)
- Number of arms
- 2
- Model description
- Randomized, 1:1, open-label, multicenter trial
| Arm | Type | Receives |
|---|---|---|
| Chest Compression Only CPR (CO-CPR) | Experimental | Other: Chest Compression Only CPR (CO-CPR) performed by trained bystanders after instructions from dispatchersInstructions from a dispatcher at the dispatch center to trained bystanders to perform CO-CPR with chest compressions only. |
| Standard CPR (S-CPR) | Active comparator | Other: Standard CPR (S-CPR) performed by trained bystanders after instructions from dispatchersInstructions 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. |
Who may qualify
- Ages
- 18 years and older
- Sex
- All
- Healthy volunteers
- Not accepted
- Age groups
- Adult, Older adult
Key inclusion criteria (3 listed)
- 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
Key exclusion criteria (10 listed)
- 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
Eligibility is decided by the study team after screening; this overview does not establish that a patient qualifies. Full inclusion and exclusion criteria.
Interventions
| Intervention | Type | Arms |
|---|---|---|
| Chest Compression Only CPR (CO-CPR) performed by trained bystanders after instructions from dispatchersAlso: Chest compression only CPR, Compression only CPR, Hands-only CPRInstructions 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 | Chest Compression Only CPR (CO-CPR) |
| Standard CPR (S-CPR) performed by trained bystanders after instructions from dispatchersAlso: Standard CPRInstructions 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 | Standard CPR (S-CPR) |
Primary outcome
30-day survival
Time frame: 1 month
Survival to 30 days after cardiac arrest
3 secondary outcomes
1-day survival
Time frame: 1 day
1-year survival
Time frame: 1 year
Survival with good neurologic outcome at discharge
Time frame: 30 days
Results and safety
This study is still under way. Results are not available in the source record yet.
Research links
- Official record on ClinicalTrials.govLast updated by the sponsor 8 May 2026.
- Derived from this study: PubMed 42838476Boberg E, Merigo G, Riva G, Ringh M, Ristagno G, Jonsson M, Nordius C, Magliocca A, Skrifvars MB, Byrsell F, Jonsson F, Claesson A, Svensson L, Nordberg P, Nord A, Hollenberg J. Design and rationale of the TANGO2 trial: A randomized controlled non-inferiority trial of bystander compression-only CPR versus standard CPR in out-of-hospital cardiac arrest. Am Heart J. 2026 Oct 6:107623. doi: 10.1016/j.ahj.2026.107623. Online ahead of print.
- Individual participant dataSharing planned: No. Data will be published on group level only
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Referral and contact
AzTrials does not enrol participants or take referrals. Contact the study team or a site listed below; they decide who can take part.
Jacob Hollenberg, MD, PhD principal investigator
Karolinska Institutet
Giuseppe Ristagno, MD, PhD study chair
University of Milan
Gabril Riva, MD, PhD study chair
Karolinska Institutet
2 sites in 2 countries: see every site and its status.
Questions about this trial
What is this clinical trial studying?
A study testing Chest Compression Only CPR (CO-CPR) performed by trained bystanders after instructions from dispatchers and Standard CPR (S-CPR) performed by trained bystanders after instructions from dispatchers in people with Out-Of-Hospital Cardiac Arrest and Cardiac Arrest, run by Karolinska Institutet at 2 sites in 2 countries.
The full registered description is in the About this study section and the official record.
Who may be eligible to take part?
The sponsor lists 3 inclusion and 10 exclusion criteria. Eligibility is decided by the study team after screening, so read the full criteria and contact a listed site.
Is this clinical trial currently recruiting?
The record says: looking for participants now, as of the sponsor's last update on 8 May 2026. Status can change between updates, so confirm with the study contact before making plans.
Where is the study taking place?
The record lists 2 sites in Italy, Sweden. Whether a site is taking part right now should be confirmed with that site. See every site.
What are the possible benefits and risks?
They depend on the study and the treatment, and no study can promise a benefit. The study team explains the known risks during informed consent, before anyone joins; the record itself does not list them.
Are results available for this study?
This study is still under way. Results are not available in the source record yet.
How can a doctor refer a patient or contact the research team?
Contact Jacob Hollenberg, MD. PhD (004686163816, jacob.hollenberg@ki.se), or a site near the patient. AzTrials does not enrol participants or take referrals.
What does the primary outcome measure?
30-day survival (time frame: 1 month). It is what the study was designed to measure, not a finding.
Where can I read the original study information?
On the ClinicalTrials.gov record for NCT03981107, which also lists 1 linked publication.
Does a listing mean the treatment is approved or proven to work?
No. A listing means the study is registered. It does not show that the treatment is safe, works, or is approved by a regulator.
How often is this information updated?
AzTrials copies changed records from ClinicalTrials.gov every night and reloads the whole registry every week. The sponsor last updated this record on 8 May 2026.