TITLE PAGE

Title: Compression-only cardiopulmonary resuscitation in improving bystanders’ cardiopulmonary resuscitation performance: a literature review

Word Counts: 4154

Keywords: bystanders’ cardiopulmonary resuscitation; compression-only cardiopulmonary

resuscitation; out-of-hospital cardiac arrest; cardiopulmonary resuscitation training

Authors’ names, credentials and affiliation:

1. Rachel Ko Jia Min, RN, Bachelor of Science (Nursing) (Hons). Email:

korachel91@gmail.com Mailing address: Alice Lee Centre for Nursing Studies,

Yong Loo Lin School of Medicine, National University of Singapore. Level 2,

Clinical Research Centre, Block MD11 10 Medical Drive, Singapore 117597\

2. Vivien Wu Xi, RN, Med. Email: nurwux@nus.edu.sg Mailing address: Alice Lee

Centre for Nursing Studies, Yong Loo Lin School of Medicine, National University of

Singapore. Level 2, Clinical Research Centre, Block MD11 10 Medical Drive,

Singapore 117597

3. Swee Han Lin, Associate Professor and Senior Consultant (Emergency), Email:

lim.swee.han@sgh.com.sg. Mailing address: Department of Emergency Medicine,

Block 1, Level 2, Outram Road, Singapore 169608

4. Wilson Tam Wai San, PhD, Assistant Professor, Statistician, Email: Wilson_tam@nuhs.edu.sg. Mailing address: Alice Lee Centre for Nursing Studies, Yong Loo Lin School of Medicine, National University of Singapore. Level 2, Clinical Research Centre, Block MD11 10 Medical Drive, Singapore 117597

5. Corresponding Author: Sok Ying Liaw, RN, PhD in Health Professional Education,

Assistant Professor, Alice Lee Centre for Nursing Studies, Yong Loo Lin School of

Medicine, National University of Singapore, Singapore. Email:nurliaw@nus.edu.sg;

Mailing address: Alice Lee Centre for Nursing Studies, Yong Loo Lin School of

Medicine, National University of Singapore. Level 2, Clinical Research Centre, Block

MD11 10 Medical Drive, Singapore 117597

1

ABSTRACT

Background: Compression-only cardiopulmonary resuscitation (CPR) has been advocated as

a preferable approach for bystanders in an out-of-hospital cardiac arrest (OHCA) event as it

has been associated with an increased chance of survival. The elimination of mouth-to-mouth

(MTM) ventilation also addresses some of the barriers to performing CPR. The aim of this

study is to undertake a literature review investigating the effectiveness of compression-only

CPR in improving rescuers’ CPR performance as compared to standard CPR.

Methods: A literature search was conducted in the following databases: Cumulative Index to

Nursing and Allied Health Literature (CINAHL), Science Direct, Scopus and PubMed from

January 2003 to January 2014, to include research studies that compared compression-only

CPR with standard CPR on participants above the age of 21, and reported quality of CPR

performance as the primary outcome.

Findings: Of the 3004 articles retrieved, 16 met the inclusion criteria. The reviewed studies

revealed that compression-only CPR requires a shorter time to initiate CPR and delivers a

higher number of total compressions. The depth of compressions in compression-only CPR

performed may be shallower than that of standard CPR due to greater rescuer fatigue. It

therefore remains inconclusive if compression-only CPR can deliver a higher number of

adequate compressions over extended periods of time. It is also unclear if simplified CPR can

improve skill retention level in the long run.

Conclusion: More studies are needed to determine whether compression-only CPR can

indeed help improve rescuers’ CPR performance. Future research efforts, together with

resuscitation policy and practice implications, are needed to further improve rescuers’ CPR

performance with the ultimate goal to enhance OHCA survival rates.

2

INTRODUCTION

It is well established that in the American Heart Association and Emergency Cardiovascular

Care (AHA ECC) “Adult Chain of Survival” concept, the provision of early bystander

cardiopulmonary resuscitation (CPR) is crucial in improving survival outcomes in out-of-

hospital cardiac arrest (OHCA). The current CPR algorithm follows a C-A-B sequence

(Chest compressions, Airway, Breathing), where the lay rescuer provides compressions and

ventilations in a ratio of 30:2 until help arrives.1

Despite promulgation of its importance in successful resuscitation, the prevalence of

bystander CPR remains critically low worldwide, ranging from as low as 1% to 44%.2

Various studies have been carried out to explore the barriers rescuers face to performing

CPR. Reasons cited often include a fear of disease transmission related to performing MTM

ventilation, a lack of confidence, a fear of poor performance and potential legal

implications.3-5 OHCA survival rates vary widely around the world, ranging from 2% to 11%,

which is still an overall low. Poor survival outcomes also suggest a low quality of bystander

CPR performance.6

To address these concerns, AHA introduced the concept of simplifying standard CPR,

also known as “hands-only CPR” or “compression-only CPR”, which has been advocated as

a preferable alternative approach in an OHCA event.7 For discussion purposes, this review

will use the term “compression-only CPR”. The compression-only CPR removes the step of

MTM ventilation during the resuscitation process, and the lay rescuer performs compressions

solely at a rate of about 100 per minute. The elimination of MTM ventilation addresses some

of the barriers to performing CPR, and hence may improve bystander CPR rates.7,8 In the

recent decade, to justify the elimination of ventilations from the bystander CPR sequence,

several studies have been conducted to compare the effectiveness of compression-only CPR

with standard CPR.9-14

Recognizing the importance of delivery high quality of CPR performance in

improving the survival rates among OHCA cases,13-14 this review aims to present the best

available evidence on the effectiveness of compression-only CPR in improving rescuers’

CPR performance as compared to standard CPR. In order to evaluate the effectiveness of the

compression-only CPR, the individual components of CPR performance were studied, i.e.

time taken to initiate CPR, number and depth of compressions, rescuer fatigue, and retention

of skill. This is done by addressing the following PICO question: (Population) in adult

3

rescuers (above 21 years old), how does (Intervention) compression-only CPR compared to

(Control) standard CPR (Outcome) affect CPR performance? (Table 1).

METHOD

Search method and process

A literature search was conducted in the following databases: CINAHL, Science Direct,

Scopus and PubMed. The key search terms used in various combinations were

“cardiopulmonary resuscitation”, “resuscitation”, “CPR”, “compression focus”, “compression

only”, “continuous chest compression”, “bystander CPR” or “rescuer”. The reference lists of

each retrieved paper were also reviewed for additional relevant journals. The search was

limited to journals published from January 2003 to January 2014, as recent publications may

be more relevant to current CPR guidelines.

Inclusion and exclusion criteria

The inclusion criteria were the following: (1) articles published from January 2003 to January

2014; (2) primary research studies in which the intervention was compression-only CPR,

compared to standard CPR; (3) research conducted on any adult participants above the age of

21, including medical staff and lay people; (4) research conducted on manikin models; and

(5) English language publications. The exclusion criteria included (1) conference

proceedings, letters to editors and opinion articles; (2) animal studies; and (3) clinical studies

which compared compression-only CPR and standard CPR in terms of out-of-hospital cardiac

arrest survival outcomes.

Search outcomes and study characteristics

The review yielded 58 potential articles. Each journal article was then read in full text to

determine its relevance. The search process is illustrated in the PRISMA flow diagram

(Figure 1). A total of 42 articles were excluded. Finally, 16 articles were appraised by two

reviewers using the Joanna Briggs Institute critical appraisal checklist for experimental

studies.15 These articles were included in the review as they met the pre-determined

proportion of all criteria - more than six “Yes” out of the 10 criteria indicated in the checklist.

4

Of the 16 reviewed articles, 12 were studies that compared the effectiveness of

compression-only CPR teaching with standard CPR teaching. The remaining four compared

the effectiveness of compression-only CPR with standard CPR dispatcher instructions. While

five studies were conducted on healthcare professional or medical students, the rest of the

studies involved laypeople. A detailed summary of the included studies can be found in

supplementary table 1 (available online only). Findings of these studies were pooled together

and categorized into the following two themes for discussion – quality of skill performance

and retention of skill. The first theme is sub-categorized into the following three subthemes –

time taken to initiate CPR, quality of compression and rescuer fatigue.

Data synthesis

Meta-analysis was performed for the thematic outcomes if two or more studies

reported the same outcome using the same measurement. Mean difference was used as effect

measure and random effects model was used to pool the results from individual studies.16 The

combined estimated and the corresponding 95%. C.I. were presented in the forest plots.

Heterogeneity was assessed by I2. All the analyses were computed using Review Manager 5.2

FINDINGS

Quality of skill performance

Time taken to initiate CPR

Five studies investigated the time taken to initiate compressions in both types of CPR; four

were randomized controlled trials that compared compression-only and standard CPR

dispatcher instructions 17-20 while one was a randomized study of a compression-only CPR

teaching intervention.21

All five studies reported unanimously that a shorter time is taken to initiate

compression in compression-only CPR.17-21 The study designs in the dispatcher studies were

similar – untrained participants were randomized to receive either compression-only or

standard CPR dispatcher instructions and were asked to manage a cardiac arrest victim. In

another study by Heidenreich, 21 which explored the ability of 53 medical students to deliver

80 compressions per minute in both compression-only and standard CPR, the time difference

in initiating compressions between the two CPR techniques was evaluated. Findings also

5

revealed that the time taken to initiate compressions in compression-only CPR was shorter by

25 seconds as compared to standard CPR.21 Results from these studies suggest that using

compression-only CPR means it takes a shorter time to initiate compressions than when using

standard CPR in both trained and untrained performers.

Three studies provided the data on the time taken to first compression for both the

compression-only or standard CPR group. 17, 19, 20 As Woollard reported the median and the

range of time taken to first compression, 20 the mean and standard deviation were computed

for the study using standard formula. 22 The forest plot is shown in Figure 2. The combined

mean difference of the time taken to first compression between the compression-only or

standard CPR was -39.2 secs (95% CI: -65.7, -12.7, p=0.004).

Quality of compression – number of compressions

Four studies compared the number of compressions performed between compression-only

and standard CPR. All of these studies showed a higher number of compressions delivered at

any time point by the compression-only CPR group during the test.18 20 23 24 This was reported

to be due to the presence of “hands off” moments, where compression was paused for

rescuers to perform MTM ventilation in standard CPR.17 21 24 25 26 With more frequent and

longer interruptions in standard CPR, some studies reported that compression-only CPR

could deliver approximately twice as many compressions per minute as compared to standard

CPR. 25

Two studies provided the data of the total number of compression in 2-minute period

and the combined mean difference between compression-only and standard CPR was 62.8

(95% C.I. 56.7, 69.0, p<0.001). This finding implies that the subjects in compression-only

CPR group were on average compressed 62.8 more than those in the standard CPR group (see

Figure 3). 26 33

Quality of compression – number and proportion of adequate compressions

Apart from evaluating the number of compressions delivered, three studies17 24 26 explored the

number or proportion of adequate compressions performed. Compressions that met the

recommended depth according to guidelines during the time when the study was undertaken

were considered “adequate” (e.g. more than 35mm).24 Two of these three studies reported that

compression-only CPR resulted in a higher number of adequate compressions.24 26

6

In a randomized crossover study by Heidenreich et al, 53 medical students were

randomized to perform either compression-only or standard CPR for nine minutes. The

researchers found that compression-only CPR delivered a significantly higher number of

adequate compressions in the first two minutes. Although the difference between both types

of CPR diminished after the second minute, the overall number of adequate compressions

was still higher in compression-only CPR than standard CPR.24 This study design was also

replicated in another study on 17 retired healthcare professionals. In contrast, this study

reported that standard CPR resulted in significantly more adequate compressions in all but

the first minute of the test. A significantly higher number of people also took rest breaks in

the compression-only CPR group as compared to standard CPR.27 Two studies by

Heidenreich et al, reported the number of compression in the first minute.

The results from both studies suggested that rescuer fatigue is more likely to affect

older people. Age was identified as a factor that may limit the effectiveness of compression-

only CPR to a shorter time period.24 Variations in response to fatigue were also reported in

different age groups. While younger rescuers tend to reduce compression depth, an older

population may take breaks and perform fewer numbers of compressions with shallower

depth.26

In a similar study, Nishiyama et al recruited 243 laypeople and randomly assigned

them to either the compression-only or standard CPR group, each with prior training

provided. Each test session lasted two minutes and the researchers reported that the net

number of appropriate chest compressions was higher in the compression-only CPR group. 26

However, a study by Hong et al28 reported otherwise. They compared the time-dependent

changes in compression depth for both compression-only and standard CPR in 852

participants, comprising both hospital workers and laypeople. The study found that the mean

proportion of correct compression depth decreased more significantly throughout the time

sectors in compression-only CPR as compared to standard CPR.28

Although the population in the Nishiyama et al study was more representative of a

general population, the test period of two minutes might not have been lengthy enough to

allow for fatigue to take effect.26 Deterioration in adequate chest compressions after two

minutes has been reported by other studies, hence a longer test period would have allowed the

researchers to better assess bystander CPR performance while taking fatigue into

consideration.24

7

The outcomes from the reviewed studies were inconclusive due to incongruent

findings. It is unclear if compression-only CPR results in a higher number and proportion of

adequate compressions. This has been found to be associated with rescuer fatigue, which is in

turn dependent on a host of individual characteristics, such as age and gender.24 Rescuer

fatigue is also largely dependent on the time duration of the test. Such factors may account

for the wide variability in the results reported across the studies.

Adequate number of compression in the first minute was reported in two studies but

the combined result (see Figure 4) was not significant with mean difference 2.53 (95% C.I. -

23.9 to 28.9, p=0.85). 24, 27 Adequate number of compression in 2-minute period was reported

by two other studies and the pooled mean difference was 31.9 with 95% C.I. from 21.0 to

42.9. The findings imply that the subjects in compression-only CPR group were on average

adequately compressed 31.9 more than those in the standard CPR group (see Figure 5). 26, 33

Rescuer fatigue

Six articles explored the effect of rescuer fatigue in both compression-only and standard

CPR. An analysis of these articles demonstrated that rescuer fatigue affects compression-only

CPR to a greater extent. Trowbridge et al measured fatigue in 20 female participants through

objective and subjective measures.29 The study reported that compression-only CPR required

greater effort, was harder to sustain and thus involved greater rescuer fatigue.28 Other studies

measured fatigue by investigating the net number of adequate chest compressions or the

proportion of adequate chest compressions, which is the number of adequate chest

compression expressed as a fraction over the total number of compressions performed. 24 27 28 30

Most reviewed studies reported a greater decrease in the number of adequate

compressions in compression-only CPR.27 28 Although the methodologies in measuring

fatigue varied among these studies, a greater rescuer fatigue was observed in compression-

only CPR. This may be due to the fact that compression-only CPR has no pauses during chest

compressions to deliver MTM ventilations. Such pauses can function as “rest time” for the

rescuer, thus with the absence of this “rest time”, it is harder to maintain the effectiveness of

compressions.29

In contrast to the abovementioned studies, a randomized trial conducted by Neset et

al investigated the perceived exertion of 64 elderly laypeople performing compression-only

and standard CPR. The researchers reported that the perceived exertion was rated to be only

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mild to moderate in the compression-only CPR group.31 Such variability in results may be

due to the presence of feedback given during the test to facilitate CPR performance, as

feedback could have mitigated the negative effects of fatigue.

Meta-analysis was not conducted for rescuer fatigue as it was measured by various

different outcomes including decline in quality of compression,30 decline in compression

force,29 compression depth,31 compression rate,28 total number of adequate compression.24, 27

For the last two studies, meta-analysis could not be conducted because they only presented

the results using bar charts. 24, 27

Retention of skill

Four studies compared CPR skill retention level in both compression-only and standard CPR. 25 26 32 33 Two studies reported overall low skill retention in both compression-only and

standard CPR.26 32 In the study by Swor et al, participants were tested on their CPR skills three

months after receiving training. The researchers found that there was overall low skill

retention in both types of CPR. 32 However, the assessment of skill retention in this study was

challenging as no formal “exit testing” was done immediately after training. Hence, the

absence of an immediate outcome to establish baseline makes it hard to compare the CPR

performances at both time points in order to determine the level of retention. In addition, as

the population sample in this study is relatively old with a mean age of 71.5 years, the results

may not be transferable in other settings as learning and skill retention abilities may vary

across ages.32

Nishiyama et al also conducted a study on 243 lay participants to assess the level of

skill retention. The resuscitation skills of the participants were evaluated immediately and

one month after training. This study found that there was a similar decrease in the net number

and proportion of adequate chest compressions in both groups; therefore suggesting that skill

retention levels are equal in both types of CPR and one is not superior to the other. Findings

in both of these studies suggested that retention is poor regardless of the type CPR technique

that has been taught and skill deterioration can occur as soon as one month after training. 26

In contrast, a prospective study conducted by Heidenreich et al investigated skill

retention levels between compression-only and standard CPR. The study sample comprised a

much younger population comprising 53 first-year medical students. They were asked to

demonstrate both compression-only and standard CPR at three time points – immediately

9

after training, six and 18 months post training. The study reported that there was a decline in

standard CPR performance throughout the 18 months, whereas minimal decline was observed

in compression-only CPR.25 Similarly, a more recent study conducted by Nishiyama et al

compared skill retention amongst 146 college students six months and one year post CPR

training. This study found that students in the compression-only CPR group performed a

significantly higher number and proportion of adequate chest compressions one year after

training, lending support to the superiority of compression-only CPR. 33

The results in these reviewed studies may differ due to different characteristics among

the studies’ sample populations, such as the mean age of the participants and whether or not

they are medically trained. In addition, the multiple testing sessions over a time period of 18

months might have allowed the students to “practice” performing CPR, thus masking true

degradation and the actual level of skill retention.25, 33

Meta-analysis was not conducted for the retention of skills as the studies measured the

outcome using different instrument/scale at different time points including one month by

number of adequate compression, 26 three months by skill performance, 32 six and eighteen

months by number of compressions, 25 six months and one year by various resuscitation skills. 33

DISCUSSION

The review summarized current evidence on the effectiveness of compression-only CPR in

improving CPR performance. Survival rates decrease by 7–10% for every minute that passes

between collapse and defibrillation if no CPR is provided; hence it is crucial for

compressions to be initiated as soon as possible from the time of collapse.34 The reviewed

studies have all shown that compression-only CPR required a shorter time to initiate CPR as

compared to standard CPR. However, these studies were conducted prior to the current

standard CPR. The previous standard CPR guideline required rescuers to deliver two rescue

breaths before compressions.1 Therefore, this required more time for standard CPR to initiate

compression. Following current guidelines, there is a need for future research to shift its

focus and compare the interruptions to compressions rather than the time taken for CPR

initiation between the two CPR techniques. 3

High-quality CPR requires compressions to be performed at an adequate depth and

rate and with minimal interruption.7 In standard CPR, MTM ventilation often results in

10

frequent and lengthy interruptions during compressions in standard CPR; thus compression-

only CPR can deliver a significantly higher number of compressions per minute.35

However, compression-only CPR has several limitations. Studies have shown that

rescuer fatigue affects compression-only CPR more than standard CPR. In compression-only

CPR, the depth of compression declined more rapidly over time.24, 28 Although compression-

only CPR can deliver a higher number of compressions, there may be fewer adequate

compressions as compared to standard CPR. It is not known which factor of compression –

number or adequacy – has a stronger impact on successful resuscitation.24 Notably, clinical

studies have reported that the total number of compressions delivered per minute can improve

survival.36 37 Thus, compression-only CPR may compensate for its lack of depth in

compressions with a higher number of compressions being performed.27

Rescuer fatigue can have a greater effect on the bystander performing compression-

only CPR due to the absence of “rest time”. Consequently, the effectiveness of compressions

can be limited to a certain time period.24 This time period is associated with rescuer fatigue,

which is in turn dependent on a range of the rescuer’s characteristics, such as age, gender and

physical fitness.38 As previous studies have reported incongruent results, the effectiveness of

compression-only CPR for a prolonged duration and its efficacy in increasing CPR skill

retention remain unknown.

A limitation that most of the reviewed experimental studies noted is the lack of

realism in their intervention design.19 20 25 26 28 33 Most studies adopted a case-based scenario,

whereby elements of the test such as the recording manikin and test duration did not mimic

that of a realistic OHCA event. The recording manikin used was in its standard clothing and

laid freely accessible to the study participants, which is unlikely to happen in reality.39 Some

studies tested CPR performance for two minutes, which was not realistic considering that

ambulance response times are generally longer than two minutes.24 The lack of realism

implies that the stress of an OHCA event is not replicated during the test.31 Thus, results from

these studies cannot be said to be applicable in an actual medical emergency, as CPR

performance may vary under different levels of stress and there may be more room for

error.21 33 “Effective” CPR performed on a manikin may not be clinically meaningful;

therefore, future research could aim to study rescuers’ ability to perform CPR under more

realistic conditions. For example, by using a simulated test scenario, the physical and

emotional demands of an OHCA event can be more realistically presented and CPR

performances can be clinically meaningful to a greater extent.25 26

11

In addition, the details of the compression-only CPR testing were not included; most

studies did not explicitly state if study participants in the compression-only CPR group

performed continuous compressions throughout the test duration or whether breaks were

implemented during the cycle. This ambiguity concerning the rest period may account for the

variation in results as studies have shown that providing breaks at a particular time during

continuous chest compressions can help reduce fatigue, hence maintaining compression depth

for an extended period of time.40 Future studies investigating the effect of rescuer fatigue in

compression-only CPR can help build evidence for the ideal rescuer-changing strategy (e.g.

switching rescuers at an interval of two minutes) and hopefully maintain high-quality chest

compressions over time.

A number of studies also had a selection bias, as study participants were medical

students or healthcare workers. 25 27 28 They do not resemble a lay population, as they possess a

strong medical background and increased exposure to CPR experience. CPR training has

mostly been tailored to the needs of this niche group of people who are professionally obliged

to perform CPR. Limited studies have been conducted on laypeople, thus there is a need for

more studies to explore and better understand the psychology behind the “helping behavior”

of laypeople in an emergency situation.41 Such studies will help provide insight on the

facilitators and barriers to performing CPR and potentially provide direction on current CPR

training and education.16 41

LIMITATIONS

This literature review has limitations. Although the search strategy was undertaken carefully

and systematically, it might not have identified all of the relevant literature. We did not

search non-electronic literature, and non-English articles were excluded. Next, the reviewers

were not blinded to the authorship of the studies during the process of critical appraisal,

however, none of the reviewers were affiliated to any authors of the reviewed studies.

Finally, this review has relatively small number of eligible articles that met the inclusion

criteria and their methodological approaches could have introduced bias.

12

CONCLUSION

This literature review has sought to present the best available evidence on the effectiveness of

compression-only CPR in improving bystander CPR performance. It revealed that

compression-only CPR requires a shorter time to initiate CPR and delivers a higher number

of total compressions. The depth of compressions performed may be shallower than that of

standard CPR due to greater rescuer fatigue. However, due to the paucity of existing studies,

it remains inconclusive if compression-only CPR can deliver a higher number of adequate

compressions in extended periods of time. It is also unclear if simplified CPR can improve

skill retention level in the long run. Evidently, more randomized studies are needed to

determine whether compression-only CPR can indeed help improve rescuers’ CPR

performance. These studies could be conducted on laypeople and the quality of chest

compression could be evaluated over a longer period of time. Future research efforts,

together with resuscitation policy and practice implications, are needed to further improve

rescuers’ CPR performance with the ultimate goal to enhance OHCA survival rates.

13

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Table 1: PICO Comprehensive review

Categories Criteria

Population Adult participants who are above the age of 21 and of any sex, ethnic background, social status and geographical area. Medical students and healthcare workers who learn compression-only CPR are also included in the study.

Intervention Experimental studies that focus on bystander CPR using either “hands-on CPR” or “compression-only CPR” as intervention.

Control Standard CPR using compression and ventilation in a ratio of 30:2

Outcome CPR performance including time taken to initiate CPR and quality of compression

Rescuer fatigue in bystander CPR CPR skill retention

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