Effective compression ratio—A new measurement of the quality of thorax compression during CPR

doi:10.1016/j.resuscitation.2012.10.016

Resuscitation

Volume 84, Issue 5, May 2013, Pages 672-677

https://doi.org/10.1016/j.resuscitation.2012.10.016 Get rights and content

Abstract

Purpose

Computer-based feedback systems for assessing the quality of cardiopulmonary resuscitation (CPR) are widely used these days. Recordings usually involve compression and ventilation dependent variables. Thorax compression depth, sufficient decompression and correct hand position are displayed but interpreted independently of one another. We aimed to generate a parameter, which represents all the combined relevant parameters of compression to provide a rapid assessment of the quality of chest compression—the effective compression ratio (ECR).

Methods

The following parameters were used to determine the ECR: compression depth, correct hand position, correct decompression and the proportion of time used for chest compressions compared to the total time spent on CPR. Based on the ERC guidelines, we calculated that guideline compliant CPR (30:2) has a minimum ECR of 0.79. To calculate the ECR, we expanded the previously described software solution. In order to demonstrate the usefulness of the new ECR-parameter, we first performed a PubMed search for studies that included correct compression and no-flow time, after which we calculated the new parameter, the ECR.

Results

The PubMed search revealed 9 trials. Calculated ECR values ranged between 0.03 (for basic life support [BLS] study, two helpers, no feedback) and 0.67 (BLS with feedback from the 6th minute).

Conclusion

ECR enables rapid, meaningful assessment of CPR and simplifies the comparability of studies as well as the individual performance of trainees. The structure of the software solution allows it to be easily adapted to any manikin, CPR feedback devices and different resuscitation guidelines (e.g. ILCOR, ERC).

Introduction

Computer-based feedback systems improve the quality of training in cardiopulmonary resuscitation (CPR),1, 2 as the performance achieved is assessed and compared with the required limits specified in the current CPR resuscitation guidelines. Such systems are used to evaluate the performance of the rescuers and are increasingly integrated into defibrillators. The intention is to improve CPR quality during cardiac arrest and to collect data for debriefing after the event, as this was shown to be an important improvement to CPR.³ These integrated feedback recordings might also be used for resuscitation research.⁴

To assess the quality of CPR, independent parameters (thorax compression depth,⁵ no-flow time,6, 7, 8 correct hand position,⁹ and compression rate4, 10) are recorded and displayed. This may result in inconsistent performance results, as a CPR trainee might achieve proper compression depth and rate but with the wrong hand position, there may be a long no-flow time, or insufficient decompression. This may provide a false impression of effective chest compressions for that specific candidate, if not every parameter is analysed. For example, this kind of performance report does not detect if two errors occur at the same time (leading to one incorrect compression) or if two errors happen at two different compressions (leading to more ineffective CPR). The same applies to the reporting of CPR study results.

To facilitate the assessment of individual CPR performance and the results from CPR studies, we tried to integrate the relevant parameters of CPR into a new combined parameter, bringing together both chest compression parameters and hands-off-time, resulting in no-cardiac flow time. We intended to calculate a single ratio describing the overall performance of guideline conform CPR with the purpose of facilitating teaching and training, and called the new parameter “effective compression ratio” (ECR).

Section snippets

Calculation of the “effective compression ratio” (ECR)

To analyse and describe thorax compression during CPR we have introduced a combined parameter, effective compression (EC), which we have used in previous studies4, 10 (Fig. 1a). A thorax compression was considered effective if the hand position was correct, the correct compression depth was achieved and the subsequent decompression was complete. The purpose of the effective compression was to provide a general overview of the quality of chest compressions. Because an effective compression is a

Results of PubMed literature search

Our PubMed search in August 2011 revealed 17 trials. After applying the exclusion criteria (2005 CPR guidelines and the needed parameters to calculate the ECR) and reviewing the studies, we were able to include 9 trials in which the correct compressions [%] and no-flow time were published. Interestingly, the ECR values were between 0.03 (for basic life support with two rescuers and no feedback)⁹ and 0.67 (for basic life support with feedback after 6 min of CPR).¹⁴ Details and a summary of the

Discussion

We computed a new parameter, “effective compression ratio”, to describe the quality of CPR, combining chest compression parameters with ventilation time reflecting the duration of no cardiac flow during CPR using a software macro. These calculations provide a single meaningful haemodynamic figure to compare the effectiveness and quality of the CPR and how compliant that performance is to current resuscitation guidelines. To prove its applicability, we calculated the ECR for previously published

Conclusion

The combined parameter “effective compression ratio” was developed to measure the quality of CPR, integrating “effective compression” (including the correct hand position on the chest, guideline-compliant compression depth and proper decompression) and the real measured flow time. The ECR is an adequate parameter to assess the accuracy of CPR compared to current CPR-guidelines with a single figure. It was used to compare the quality of effective CPR in previously published studies revealing a

Conflict of interest statement

None of the authors has any conflict of interest.

Acknowledgements

We thank Emily Lemon, Julie Tremetsberger, and Jeff Crowder for the proofreading.

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While we found differences between the investigated CPR feedback devices, overall BLS quality was suboptimal in all groups. Surprisingly, effective compression was not improved by any CPR feedback device compared to standard BLS. All feedback devices caused substantial delay in starting CPR, which may worsen outcome.
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^☆: A Spanish translated version of the abstract of this article appears as Appendix in the final online version at http://dx.doi.org/10.1016/j.resuscitation.2012.10.016.

¹: Both authors contributed equally to this work.

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Simulation and educationEffective compression ratio—A new measurement of the quality of thorax compression during CPR☆

Abstract

Purpose

Methods

Results

Conclusion

Introduction

Section snippets

Calculation of the “effective compression ratio” (ECR)

Results of PubMed literature search

Discussion

Conclusion

Conflict of interest statement

Acknowledgements

Resuscitation

Resuscitation

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Resuscitation

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Resuscitation

Simulation and education
Effective compression ratio—A new measurement of the quality of thorax compression during CPR☆