Prompt recognition of cardiac arrest

In 2010, the International Liaison Committee on Resuscitation (ILCOR) conducted an evidence summary on the recognition of cardiac arrest (Koster et al., 2010). In this context, recognition of cardiac arrest includes checking the pulse and recognising agonal breathing.

To date, there are no studies that assess the accuracy of checking the pulse to detect cardiac arrest. Additionally, first aid providers have difficulty mastering the pulse check and remembering how to perform it.

There is often a high frequency of agonal gasps after cardiac arrest, but several studies showed that first aid providers and EMS dispatchers often do not recognise them. There are many terms used to describe abnormal breathing, confusing first aid providers and dispatchers alike. Sometimes these terms are limited due to cultural influences and translation limitations, even in the same country. Teaching people to identify agonal breathing using a video clip improved the accuracy of recognising cardiac arrest.

Evidence shows that with EMS dispatchers, failure to recognise cardiac arrest may be associated with a failure to follow cardiac arrest protocols while on the call. In a seizure complaint question sequence used by dispatchers, the detection of cardiac arrest cases improved after introducing the question, “Is he breathing regularly?” Special courses aimed at teaching dispatchers to identify agonal breathing also increased their ability to recognise cardiac arrest.
 

Chest compression-only CPR versus standard CPR

Many studies were conducted to evaluate chest compression-only CPR versus standard CPR with or without dispatcher instruction. We used two systematic reviews, one from ILCOR (Olasveengen et al., 2017) and one from Cochrane (Zhan et al., 2017) and the adult basic life support, 2020 international consensus on CPR from ILCOR (Olasveengen, 2020).
 

Compression-only CPR versus standard CPR

For the critical outcome of survival with favourable neurological function, a meta-analysis of two cohort studies showed no significant difference between people who received compression-only CPR compared to people who received CPR with a compression-to-rescue-breath ratio of 15:2. Further, a different meta-analysis of three studies, this time using CPR with a compression-to-rescue-breath rate of 30:2, also showed no significant difference in the outcome.

For the critical outcome of survival only, a meta-analysis of six studies did not demonstrate significant differences in people who received compression-only CPR compared to those who received standard CPR with a compression-to-rescue-breath ratio of 15:2. One study showed that people who received compression-only CPR had a worse survival rate than those who received CPR with a compression-to-rescue-breath ratio of 30:2. In another meta-analysis of three observational studies, there was no significant difference between people who received either type of CPR (compression-only or standard with a rate of 30:2).

For the important outcome of return of spontaneous circulation, a meta-analysis of three cohort studies showed no benefit to using the 15:2 ratio compared to using a different ratio.

The Cochrane systematic review compared chest-compression-only-CPR versus standard CPR on non-asphyxial out-of-hospital cardiac arrest. The meta-analysis found high-quality evidence that continuous chest compression CPR without rescue breathing improved people’s survival to hospital discharge compared to interrupted chest compressions with pauses for rescue breathing (ratio 15:2).
 

Compression-only CPR versus standard CPR (adults) – dispatcher-assisted

Low-quality evidence from a randomised controlled trial demonstrated no benefit to favourable neurological function when dispatchers provided instructions for continuous chest compressions compared to instructions for compressions and rescue breaths at a ratio of 15:2. Conversely, three randomised controlled trials also compared the two types of dispatcher-assisted CPR and found that compression-only CPR resulted in a small benefit to peoples’ survival to hospital discharge.

In the nationwide recommendation of compression-only CPR for first aid providers in Japan, results associated dispatcher-assisted compression-only CPR with improved bystander CPR rates. However, the outcome for people receiving CPR was better when bystanders performed standard CPR rather than compression-only.
 

First aid provider fatigue in chest-compression-only CPR

A comparison of first aid provider fatigue in chest compression between first aid providers who perform compression-only CPR versus standard CPR has been the subject of scoping review for the 2020 ILCOR recommendation. Fifteen manikin studies evaluating fatigue and its effects on CPR quality in volunteers performing continuous compressions and 30:2 or 15:2 CPR. They suggest that continuous compressions are effective in the first two minutes with regard to depth and frequency, and there are indications that short periods of rest (pauses in compression) reduce first aid provider fatigue and increase CPR quality.
 

Chest compression quality

Hand position during compression

The recommendations for hand position during compressions, based on only low- or very-low-certainty evidence in 2015 was reviewed in 2020. No studies reporting favourable neurological outcome, survival, or return of spontaneous circulation.  Only two observational studies that reported physiological endpoints are found. One study with a few people who received prolonged resuscitation from nontraumatic cardiac arrest observed improved peak arterial pressure and ETCO2  during compression systole when compressions were performed over the lower third of the sternum compared with the centre of the chest. The other physiological endpoints did not differ in this study and the second one, in 30 adults with cardiac arrest, observed no difference in ETCO2 values resulting from changes in hand placement.
 

Chest compression rate

The scientific foundation for chest compression rate includes an evidence summary completed by ILCOR (Perkins et al., 2015) and a scoping review by ILCOR (Considine et al., 2019) which served as the basis for the adult basic life support, 2020 International Consensus on CPR from ILCOR (Olasveengen, 2020, S41).

There was an inconsistent association between chest compression rate and survival with a favourable neurological outcome. The results varied depending on the study population (adult versus child), study size and whether any adjustments were made for potential confounders.

One study reported that when it adjusted for confounders, including compression depth and fraction , survival to hospital discharge was lower when compression rates were 80–99 and 120–139/min, compared to 100–119/min. No other studies reported specific compression rates benefitting the survival to hospital discharge outcome.

There were no significant differences reported between various chest compression rates on one-month survival, one-day survival, or hospital admission while alive. Of the eight studies that examined spontaneous circulation return, one study said that, compared to a reference chest compression rate of 100–120/min, 121–140/min was associated with an increased return of spontaneous circulation. Another study associated higher mean chest compression rates with an increased likelihood of spontaneous circulation return. None of the three studies that reported on blood pressure showed a significant effect between chest compression rate and either systolic or diastolic blood pressure.
 

Chest compression depth

The scientific foundation for chest compression depth includes an evidence summary completed by ILCOR (Travers et al., 2015 S51) and a scoping review by the Basic Life Support ILCOR task force (Considine et al., 2019). This served as the basis for the adult basic life support, 2020 International Consensus on CPR from ILCOR (Olasveengen, 2020, S41). Four observational studies suggest that the return of spontaneous circulation with a compression depth of more than 5 cm in adults is more likely than all other compression depths. Another study suggested that deeper chest compressions were associated with a greater likelihood of successful defibrillation.

For survival to hospital admission, one study showed that increased chest compression depth was associated with increased odds of admission to a hospital alive, while another study showed no association between different mean chest compression depths and survival to hospital admission.

Three studies compared different chest compression depths with survival and a favourable neurological outcome. None of the chest compression depths significantly increased or decreased survival or favourable neurological outcomes. However, one observational study suggests that a compression depth in adults of more than 5 cm increased survival and good neurological outcomes, compared to all other compression depths during standard CPR.

For survival, three studies reported statistically significant relationships between one-day survival and chest compression depth in adults. For each 5 mm increase in chest compression depth, one-day survival increased. One study that looked at survival to the emergency department showed that mean chest compression depths of 5–6 cm had the highest survival to emergency department rates in adults.

One study reported that survival to hospital discharge decreased when chest compression depth was less than 38 mm, compared to more than 51 mm and adjusting for confounders. Two adult studies reported that for each 5 mm increase in chest compression depth, survival to hospital discharge increased.

At least one study detailed injury frequency and showed that increased chest compression depths were associated with higher injury rates. The mean chest compression depth of people with injuries was 56 mm versus 52 mm in people with no injuries.
 

Chest wall recoil

The scientific foundation for chest wall recoil includes an evidence summary completed by ILCOR (Perkins et al., 2015) and a scoping review by ILCOR (Considine et al., 2019). This served as the basis for the adult basic life support, 2020 international consensus on CPR from ILCOR (Olasveengen, 2020, S41). The first two outcomes examined were favourable neurological outcomes and survival to hospital discharge. Two studies had conflicting results, while another study reported that – once adjusted for confounders – there was no difference in survival to hospital discharge associated with different chest compression release speed. One study reported the return of spontaneous circulation and showed no statistically significant improvement associated with a 10 mm per second increase in chest compression release speed. Only animal studies have found reduced coronary perfusion pressure with incomplete chest recoil.
 

Check for circulation during basic life-support

There is no evidence to justify doing further research and changing the 2015 treatment recommendation. Outside the advanced life-saving environment, there is insufficient data about the value of a pulse check while performing CPR.
 

Firm surface for CPR

For this topic, we use the adult Basic Life Support, 2020 International Consensus on CPR from ILCOR (Olasveengen, 2020, S41). Variation in backboard use and the practice of moving a person from the bed to the floor to improve the quality of CPR are reported. The identified science has been grouped by mattress type, floor compared with bed and backboard. Four manikin randomised controlled trials did not identify a difference in chest compression depth between mattress types. Two manikin meta-analyses found no effect on chest compression depth and neither two manikin trials identified a difference in chest compression depth between groups. At least, six manikin randomised controlled trials found that the effect of chest compression is improved when they are used on the backboard and one randomised controlled trial did not find a better effect. It’s important to indicate that we have no clinical studies reporting on the critical outcomes of survival and favourable neurological outcome or important outcome of chest compression quality. 

Harm caused by CPR to a person who is not in cardiac arrest

This topic’s scientific foundation includes an evidence summary from a systematic review, the Consensus of Science, and a Basic Life Support ILCOR task force treatment recommendation from Svavarsdottir et al. (2019).

Many first aid providers are concerned that they will harm a person who is not in cardiac arrest or cause severe complications by giving chest compressions. This belief makes them reluctant to start CPR. The systematic review included four observational studies that looked at 762 people who were not in cardiac arrest but still received CPR by first aid providers outside the hospital. Pooled data of three of these studies found an incidence of muscle damage of 0.3%, bone fracture (rib and clavicle) of 1.7%, pain in the area of chest compression of 8.7% and no visceral injury. The fourth study reported no injury.
 

Harm to rescuer from CPR

This topic has not been updated since 2010 and only concerned injury from CPR to people who are not in cardiac arrest (see above). It also reviewed any potential harm to the first aid providers during CPR, including harm during chest compressions, during rescue breaths, and with the use of defibrillators. Since 2008, no randomised controlled trials were identified for this topic and most identified studies addressed the safety of shock delivery during chest compressions when first aid providers wore gloves. Despite limited evidence evaluating first aid provider safety, there was a lack of published evidence supporting the interpretation that CPR is generally safe for first aid providers. Some reports demonstrate the possibility of disease transmission while performing rescue breaths and that CPR is relatively safe. Delivery of a shock with an automated defibrillator during basic life support is also safe. The incidence and morbidity of defibrillator-related injuries in the first aid providers are low. Note that these studies are all prior to COVID-19, see Pandemic.
 

CPR before calling for help

For this topic, we used the adult Basic Life Support, 2020 International Consensus on CPR from ILCOR (Olasveengen, 2020, S41). The optimal sequence for calling for help and starting CPR frequently arises during CPR education and was the subject of a new question and recommendation in 2020. Increased availability of phones and hands-free options for lone first aid providers were considered important.

For the critical outcome of survival with favourable neurological outcome, only one observational study is identified, and no meta-analysis found. This cohort study from Japan showed no benefit from a “CPR-first” strategy compared with a “call-first” strategy.

Adjusted analyses were performed on various subgroups and suggested significant improvements in survival with a favourable neurological outcome with a “CPR-first” strategy compared with a “call-first” strategy for non-cardiac etiology, out of hospital cardiac arrest, under 65 years of age, under 20 years of age and both under 65 years of age and noncardiac etiology together. The overall certainty of the evidence was rated as very low. The results are not generalisable to all out of hospital cardiac arrests because they refer specifically to bystander-witnessed cases in which the bystander spontaneously initiates CPR after only a short delay.
 

Starting CPR: rescue breaths or compression?

This topic’s scientific foundation includes the ILCOR treatment recommendation from Considine et al. (2019) and the adult Basic Life Support, 2020 International Consensus on CPR from ILCOR (Olasveengen, 2020, S41). This current systematic review did not identify any additional human or manikin studies published since the 2015 ILCOR systematic review.

There are three manikin studies on whether to start CPR with chest compressions or rescue breaths. All the studies found that beginning CPR with compressions first (30:2) compared to CPR beginning with rescue breaths first (2:30) significantly decreased the time to commencement of chest compression and seemed to decrease the time needed to complete the first CPR cycle. For time to commence rescue breaths, the results are conflicting between studies. The evidence is of very low quality.

 

Compression-to-rescue-breath ratio

In 2017 ILCOR completed an evidence summary on the ratio of compressions and rescue breaths during CPR, which we used to inform this section of the scientific foundation (Olasveegen et al., 2017). A meta-analysis of two observational cohort studies looked at the critical outcome of survival with a favourable neurological function. The results demonstrated that the 30:2 compression-to-rescue-breath ratio was more beneficial compared to a different ratio. Evidence is of very low quality.

Furthermore, a meta-analysis of six cohort studies showed that the survival rate was higher in the group of people who received the 30:2 ratio compared to the group who received 15:2. One retrospective cohort showed improved survival with a rate of 50:2 compared to 15:2 compressions to rescue breaths, but the evidence is of very low quality.
 

Reducing pauses between chest compressions

For this topic, we used an evidence summary from ILCOR, completed in 2015 (Perkins et al., 2015). Some CPR guidelines recommend pausing no more than five seconds to provide rescue breaths. First aid providers also have to pause compressions when using a defibrillator during pre-shock and post-shock intervals. Pre-shock intervals refer to the time required to assess the rhythm of a person in cardiac arrest and post-shock intervals refer to the time between shock delivery and when it is safe to resume compressions. One observational study indicated that shorter pre-shock pauses benefitted shock success.

One observational study showed that limiting pre-shock and post-shock pauses benefitted the return of spontaneous circulation, while another observational study suggested that achieving chest compression fractions (i.e., the total CPR time devoted to compressions) greater than 40% also benefitted this outcome.

For the outcome of survival to hospital discharge, three observational studies with 3,327 people demonstrated that shorter pre-shock and post-shock pauses produced a better outcome for people. However, one randomised controlled trial comparing two automated external defibrillator algorithms found no differences.
 

Rhythm-check timing

This topic’s scientific foundation includes an ILCOR treatment recommendation from Ristagno et al. (2019) and the adult Basic Life Support, 2020 International Consensus on CPR from ILCOR (Olasveegen et al., 2017).

There is some correlation between the interruption of chest compressions and adverse outcomes. One of the most common disruptions is checking cardiac rhythm after defibrillation. Still, any unnecessary pausing in chest compressions might impact the result of cardiac arrest.

Regarding the outcome of survival with a favourable neurological outcome at discharge, we looked at one randomised controlled trial and three observational studies. Both the trial and the studies assessed the effect of interrupting chest compressions to check the rhythm immediately after shock delivery. The randomised controlled trial included 415 out-of-hospital cardiac arrests and showed no benefit to interrupting chest compressions. Conversely, the three observational studies, which had 763 out-of-hospital cardiac arrests,  showed harmful effects when chest compressions were interrupted.

We also looked at the available evidence to see if the same chest compression interruption (to check the rhythm right after shock delivery) affected the outcome of survival to hospital discharge. Two randomised controlled trials with 1,260 out-of-hospital cardiac arrests showed no benefit to interrupting chest compressions. In contrast, three observational studies with 3,094 out-of-hospital cardiac arrests showed harmful effects when checking the rhythm immediately after defibrillation.

Further, for the outcome of survival to hospital admission, the results from two randomised controlled trials, totalling 1.260 out-of-hospital cardiac arrests, demonstrated no benefit to interrupting chest compressions to check the rhythm right after defibrillation.

Finally, with regards to the return of spontaneous circulation, two observational studies that included 2,969 out-of-hospital cardiac arrests showed harmful effects when chest compressions were interrupted immediately after shock delivery. Additionally, data from three randomised controlled trials, looking specifically at chest compression fraction, demonstrated harmful effects when chest compressions were interrupted to check the rhythm right after shock delivery. The trials included 1,412 out-of-hospital cardiac arrests.
 

Dispatch diagnosis of cardiac arrest

For this topic, we used the adult Basic Life Support, 2020 International Consensus on CPR from ILCOR (Olasveengen, 2020, S41) and the 2019 ILCOR systematic review of the dispatch diagnosis of cardiac arrest (Drennan et al., 2019).

The review looked at out-of-hospital cardiac arrests and assessed a variety of algorithms and criteria used by dispatch centres to identify potential life-threatening events (such as cardiac arrest) to triage emergency responders to the scene appropriately. Forty-six observational studies with 84,534 adult out-of-hospital cardiac arrests demonstrated the following results:

• Dispatchers correctly identified cardiac arrest with a sensitivity of 0.79 (0.69–0.83).
• Dispatchers incorrectly diagnosed the absence of cardiac arrest when the person was experiencing it (the critical outcome of a false negative) at 0.21 (0.17–0.32).

Twelve observational studies involving 789,004 out-of-hospital cardiac arrests showed the following results:

• Dispatchers correctly identified the absence of cardiac arrest with a specificity of 0.99 (0.93–1.00).
• Dispatchers incorrectly diagnosed cardiac arrest when the person was not experiencing it (false positive) at a rate of 0.01 (0.01–0.07).

Dispatcher-assisted CPR

We used one systematic review (Nikolaou-2019-82), one evidence summary from ILCOR in 2019 to look at the topic of dispatcher-assisted CPR (Soar-2019-e826) and the adult basic life support, 2020 international consensus on CPR from ILCOR (Olasveengen, 2020, S41).

When comparing the difference between a dispatcher assisting with CPR and not assisting, evidence suggested that if the dispatcher offered assistance over the phone, survival and survival with a favourable neurological outcome at hospital discharge, and one month after cardiac arrest, all increased. The review also showed that there was a correlation between the 21 systems offering dispatcher-assisted CPR and a sustained return of spontaneous circulation. However, there was no association with increased survival to hospital admission compared to systems without dispatcher-assisted CPR.

When comparing the outcomes in cardiac arrests outside of a hospital setting, people who received dispatcher-assisted CPR from a bystander include improvements in:

• survival with a favourable neurological function, and survival in general, at hospital discharge and one month later, and
• a greater likelihood of a return of spontaneous circulation.

These improvements were more likely to occur when bystanders received assistance from dispatchers to perform CPR than when no bystander CPR occurred.

The above findings were inconsistent when compared with instances when bystanders performed CPR with the assistance of a dispatcher versus when they performed CPR without assistance. The people receiving bystander CPR with dispatcher assistance were more likely to experience a return of spontaneous circulation upon hospital arrival than when bystanders did not have dispatcher assistance. This result suggests that dispatcher-assisted CPR could be as effective as unassisted CPR.

Feedback for CPR quality

CPR feedback or prompt devices are used to improve CPR quality, as ROSC, and survival from cardiac arrest. Feedback devices can measure various aspects of CPR mechanics, including ventilation rate, chest compression quality or measures of flow time (CPR fraction, etc.). These data can be used by the provider in real-time (audible or visual metronomes, voice or visual prompts or alarm) or as a summary report at the end of a resuscitation (numeric displays, waveforms, percentage).

Three real-time CPR guidance devices were identified in studies: digital audio-visual feedback, audio and tactile “clicker” feedback for chest compression depth and release and metronome guidance for chest compression rate. Nevertheless, due to heterogeneity across studies, it was not possible to make a metanalysis.
 

Education review

59 papers were identified through our search strategy as having insights to support adults learning CPR. Many supported insights covered elsewhere in these Guidelines concerning educational approaches and learning methodologies, but the evidence set out below indicates issues most specific to CPR.

Adaptation and prioritisation

• Papalexopoulou et al., 2014; Sopka et al, 2013, identify the need for adaptation of educational tools (e.g. manikins and defibrillators), locations (e.g., waterfront scenarios for lifeguards) and methods to make them accessible and appropriate for learners’ needs and abilities.
• Tweed and Wilson, 1977 advocate first aid education providers to prioritise training community members most likely to encounter cardiac arrest emergencies in CPR such as medics, police officers, firefighters and lifeguards. They suggest that these groups, given their status and role in the community, might make effective educators for the general public.
• Huang et al. 2016 identify people with family members who are at high risk of cardiac arrest due to illness as being more motivated to learn first aid (see also Motivation to learn).

Barriers and challenges to learning

• Some bystanders have concerns about disease exposure and transmission through standard CPR, which has caused a significant decrease in their willingness to provide it to both strangers and family members. Compression-only CPR is the preferred method (Cheng-Yu et al., 2016; Jelinek et al., 2001; Lam et al., 2007; Pei-Chuan Huang et al., 2019).
• For practical CPR courses, there is limited evidence to demonstrate that female-only learner groups are beneficial to female learners, but there is evidence to support that males are more likely to learn in mixed groups (Sopka et al., 2013).

Enhanced scenario-based learning

• Massive multiplayer virtual worlds allow learners to play a role and experience “real-life” scenarios and environments in which to practise their CPR skills. (Creutzfeldt et al., 2013). (See also Gamification, and Online learning for adults.)

Dispatcher assisted CPR

• There is limited evidence in favour of the efficacy of dispatchers providing instructions to lay responders in giving CPR. Providing CPR instructions using video-assisted technology does not significantly improve the overall quality of bystander CPR compressions or rescue breaths (Bolle et al., 2009). However, in a study by Bolle et al. (2011) participants noted that video-equipped mobile phones should be utilised instead of audio-only phones during a medical emergency.  Given the fast-emerging technology associated with smartphones, we identify this as a gap in evidence in need of further exploration.
• Dispatchers who communicate using video-assisted emergency calls may need more training for this tool to be effective and widespread within CPR education (Bolle et al., 2009). Bang et al. (2000) suggest that dispatchers with further training (e.g. technical and emotional) are more effective.

Systematic reviews

Berdowski, J., Berg, R. A., Tijssen, J. G. P., & Koster, R. W. (2010). Global incidences of out-of-hospital cardiac arrest and survival rates: Systematic review of 67 prospective studies. Resuscitation, 81(11), 1479–1487.
http://doi.org/10.1016/j.resuscitation.2010.08.006

Considine, J., Gazmuri, R. J., Perkins, G. D., Kudenchuk, P. J., Olasveengen, T. M., Vaillancourt, C., et al. (2019). Chest compression components (rate, depth, chest wall recoil and leaning): A scoping review. Resuscitation,
http://doi.org/10.1016/j.resuscitation.2019.08.042

Considine, J., Mancini, M.E., Morley, P., Avis, S., Brooks, S., Castren, M., Chung, S., … Olasveengen, T.M. (2019). Starting CPR (ABC vs. CAB) for Cardiac Arrest in Adults and Children Consensus on Science with Treatment Recommendations [Internet]. International Liaison Committee on Resuscitation (ILCOR) Basic Life Support Task Force. Available from: http://ilcor.org

Drennan, I. R., Geri, G., Couper K, Brooks, S, Kudenchuk, P. J., Pellegrino, J, Schexnayder, S, … Morley, P. T. (2019). Criteria to diagnose cardiac arrest in dispatch centres Consensus on Science with Treatment Recommendations [Internet]. International Liaison Committee on Resuscitation (ILCOR) Basic Life Support Task Force. Available from: http://ilcor.org
https://costr.ilcor.org/document/dispatch-diagnosis-of-cardiac-arrest-systematic-review)

Koster, R. W., Sayre, M. R., Botha, M., Cave, D. M., Cudnik, M. T., Handley, A. J., … & Morley, P. T. (2010). Part 5: Adult basic life support: 2010 International consensus on cardiopulmonary resuscitation and emergency cardiovascular care science with treatment recommendations. Resuscitation, 81(1), e48-e70.
http://doi.org/10.1016/j.resuscitation.2010.08.005

Nikolaou, N., Dainty, K. N., Couper, K., Morley, P., Tijssen, J., …Vaillancourt, C. (2019). A systematic review and meta-analysis of the effect of dispatcher-assisted CPR on outcomes from sudden cardiac arrest in adults and children. Resuscitation, 138, 82–105.
http://doi.org/10.1016/j.resuscitation.2019.02.035

Olasveengen, T. M., de Caen, A. R., Mancini, M. E., Maconochie, I. K., Aickin, R., … Atkins, D. L. (2017). 2017 International Consensus on Cardiopulmonary Resuscitation and Emergency Cardiovascular Care Science With Treatment Recommendations Summary. Circulation, 136(23), III–5–17.
http://doi.org/10.1161/CIR.0000000000000541

Perkins, G. D., Travers, A. H., Berg, R. A., Castren, M., Considine, J., Escalante, R., et al. (2015). Part 3: Adult basic life support and automated external defibrillation: 2015 International Consensus on Cardiopulmonary Resuscitation and Emergency Cardiovascular Care Science with Treatment Recommendations. Resuscitation, 95, e43–69.
http://doi.org/10.1016/j.resuscitation.2015.07.041

Ristagno G, Olasveengen TM, Mancini MB, Avis S, Brooks S, Castren M, Chung S, Considine J, Kudenchuk P, Perkins G, Semeraro F, Smyth M. (2019). Rhythm check timing Consensus on Science with Treatment Recommendations [Internet] Brussels, Belgium: International Liaison Committee on Resuscitation (ILCOR) Basic Life Support Task Force, Dec 28th. Available from: https://costr.ilcor.org/document/rhythm-check-timing-tfsr-costr

Soar, J., Maconochie, I., Wyckoff, M. H., Olasveengen, T. M., Singletary, E. M., Greif, R., et al. (2019). 2019 International Consensus on Cardiopulmonary Resuscitation and Emergency Cardiovascular Care Science With Treatment Recommendations: Summary From the Basic Life Support; Advanced Life Support; Pediatric Life Support; Neonatal Life Support; Education, Implementation, and Teams; and First Aid Task Forces. Circulation, CIR0000000000000734.
http://doi.org/10.1161/CIR.0000000000000734

Svavarsdottir H, Olasveengen TM, Mancini MB, Avis S, Brooks S, Castren M, Chung S, … Morley PT. (2019). Harm from CPR to Victims Not in Cardiac Arrest Consensus on Science with Treatment Recommendations. International Liaison Committee on Resuscitation (ILCOR) Basic Life Support Task Force. Available from: http://ilcor.org

Travers, A. H., Perkins, G. D., Berg, R. A., Castren, M., Considine, J., Escalante, R., et al. (2015). Part 3: Adult Basic Life Support and Automated External Defibrillation. Circulation, 132(16 suppl 1), S51–S83.
http://doi.org/10.1161/CIR.0000000000000272

Zhan, L., Yang, L. J., Huang, Y., He, Q., & Liu, G. J. (2017). Continuous chest compression versus interrupted chest compression for cardiopulmonary resuscitation of non-asphyxial out-of-hospital cardiac arrest. Cochrane Database of Systematic Reviews, 25(23), 1546–48.
http://doi.org/10.1002/14651858.CD010134.pub2

Non-systematic reviews

Bobrow, B. J., Spaite, D. W., Berg, R. A., Stolz, U., Sanders, A. B., Kern, K. B., et al. (2010). Chest compressiononly CPR by lay rescuers and survival from out-of-hospital cardiac arrest. JAMA: the Journal of the American Medical Association, 304(13), 1447–1454.
http://doi.org/10.1001/jama.2010.1392

Jiang, C., Jiang, S., Zhao, Y., Xu, B., & Zhou, X. L. (2015). Dominant hand position improves the quality of external chest compression: a manikin study based on 2010 CPR guidelines. The Journal of Emergency Medicine, 48(4), 436-444.
DOI: 10.1016/j.jemermed.2014.12.034

Kazaure, H. S., Roman, S. A., & Sosa, J. A. (2013). Epidemiology and outcomes of in-hospital cardiopulmonary resuscitation in the United States, 2000-2009. Resuscitation, 84(9), 1255–1260.
http://doi.org/10.1016/j.resuscitation.2013.02.021

Wang, J., Tang, C., Zhang, L., Gong, Y., Yin, C., & Li, Y. (2015). Compressing with dominant hand improves the quality of manual chest compressions for rescuers who performed suboptimal CPR in manikins. American Journal of Emergency Medicine, 33(7), 931–936.
http://doi.org/10.1016/j.ajem.2015.04.007

Education references

A., Herlitz, J., & Holmberg, S. (2000). Possibilities of Implementing Dispatcher-Assisted Cardiopulmonary Resuscitation in the Community: An Evaluation of 99 Consecutive Out-of-Hospital Cardiac Arrests. Resuscitation, 44(1), 19-26.

Bolle, S., Johnsen, E., & Gilbert, M. (2011). Video Calls for Dispatcher-Assisted Cardiopulmonary Resuscitation can Improve the Confidence of Lay Rescuers-Surveys After Simulated Cardiac Arrest. Journal of Telemedicine and Telecare, 17(1), 88-92.

Bolle, S., Scholl, J., & Gilbert, M. (2009). Can Video Mobile Phones Improve CPR Quality When Used for Dispatcher Assistance During Simulated Cardiac Arrest? Acta Anaesthesiol Scandinavica, 53(1), 116-120.

Cheng-Yu, C., Yi-Ming, W., Shou-Chien, H., & Chung-Hsien, C. (2016). Effect of Population-Based Training Programs on Bystander Willingness to Perform Cardiopulmonary Resuscitation. Signa Vitae-A Journal in Intensive Care and Emergency Medicine, 12(1), 63-69.

Creutzfeldt, J., Hedman, L., Heinrichs, L., Youngblood, P., & Fellander-Tsai, L. (2013). Cardiopulmonary Resuscitation Training in High School Using Avatars in Virtual Worlds: An International Feasibility Study. Journal of Medical Internet Research, 15(1), 1-14.

Huang, Q., Hu, C., & Mao, J. (2016). Are Chinese students willing to learn and perform bystander cardiopulmonary resuscitation? Journal of Emergency Medicine, 51(6), 712–720.
DOI: 10.1016/j.jemermed.2016.02.033

Jelinek, G., Gennat, H., Celenza, T., O’Brien, D., Jacobs, I., & Lynch, D. (2001). Community Attitudes Towards Performing Cardiopulmonary Resuscitation in Western Australia. Resuscitation, 51(3), 239-246.

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