Real-time Chest Compression Fraction Measurement
Authors
Guy C. Gilbert, MS, CHSOS-A, CHSE1 Daniel J. Backlund PhD, CHSOS, CHSE2
Matthew Pierce MS, NREMT, CHSOS2
1 - Texas Tech University Health Sciences Center, Amarillo, TX
2 - Texas Tech University Health Sciences Center, Lubbock, TX
These authors have no conflicts of interest or disclosures.
Corresponding Author
Guy Gilbert, MSM, MSOL, CHSOS-A, CHSE, Texas Tech University, School of Veterinary, Amarillo, TX (Email: guy.gilbert@ttu.edu)
Abstract
The American Heart Association (AHA) recommends maintaining a Chest Compression Fraction (CCF) of 60% to 80% during Cardiopulmonary Resuscitation (CPR). Achieving an 80% CCF has been shown to increase survival by up to 300%1. The calculation of CCF is customarily done by the use of two stopwatches. One stopwatch is for the duration of the mock code and the other is for the timing of high-quality CPR. The two stopwatches are operated by the CPR coach or recorder and the calculation of CCF primarily occurs at the conclusion of the training exercise. The inability of a CPR coach or mock code team members to know if their CCF is sufficient does not allow any opportunity for the team to make real time adjustments.
Introduction
AHA introduced the CCF parameter and recommended threshold in the 2015 CPR guidelines for ACLS, BLS, and PALS. The American Heart Association has stated that a CCF between 60% and 80% increases survival outcomes2. Within the team dynamics activity, CCF is calculated manually using a two stopwatch method. The two stopwatch method does not provide a calculation of real time CCF. Currently, there is no capability to calculate and present CCF through the use of patient simulators or their associated vital sign displays. As far as the authors are aware, many of the systems that we have investigated do not show the participant either the dynamic or cumulative CCF and the exercise relies on the two-stopwatch method.
Real time CCF calculation provides code teams the opportunity to make performance adjustments during mock codes. In conjunction with feedback devices, the use of a computer-based tool provides the team with real time performance data. An example of such a tool would be a progressive web application with functionality to calculate real time CCF. Our application provides a low-resource, low-overhead supplement to any existing CPR system for providing both dynamic and cumulative CCF calculations.
Traditional CCF Calculation
American Heart Association states Healthcare providers can calculate CCF mechanically by using a feedback device or manually by using 2 stopwatches1. One stopwatch measures the total code time for code start until code stop or the return of spontaneous circulation, and a second stopwatch is meant to capture the total time of chest compressions. To measure chest compression time, the second timer is started each time compressions begin or resume and is stopped during each pause in compressions. The chest compression time is then divided by the total code time2.
With the existing method of calculating CCF manually using timers, stopwatches or AHA’s Full Code Pro application, feedback for CCF is only provided retrospectively. The method of manually calculating CCF retrospectively, does not provide real time feedback. Further applications, such as AHA’s Full Code Pro4 do not have the functionality to real time CCF. AHA Full Code Pro (FCP) 4 is a free, mobile application that allows a CPR coach to measure the time of different events and interventions during a mock code. FCP has the ability to start multiple, digital stopwatches during a mock code and document timestamps of events. The FCP user interface does not automatically calculate either the cumulative or the dynamic CCF for the users; cumulative CCF must be calculated at the conclusion of the mock code. Though FCP allows the elimination of monitoring two physical stopwatches by including both running times on one display, the calculation of the CCF still must be done manually.
Our applications eliminate the need for manual CCF calculations, whether they be dynamic or cumulative. One challenge introduced by the two-stopwatch method is small errors in the cumulative CCF value being calculated. This error is a result of the user stopping the cumulative-time stopwatch at the correct time. For a mock code lasting a duration of 10 minutes (600 seconds), a 10 second runover of the stopwatch would result in an error of approximately 1.67%. Though small, a more automated solution such as those methods implemented in applications such as FCP and our applications reduce this error by expediting the process of stopping all stopwatches. Monitoring dynamic CCF allows both the participants and the CPR coach in a mock code to assess the overall impact of external factors such as code interruptions, AED shock applications, advanced interventions, etc. Coaches can demonstrate to participants in debrief how these external factors affect CCF using the dynamic CCF calculation as a guide.
Development of a Web Application
To take advantage of readily available resources, a Progressive Web Application (PWA) was developed with the collective efforts of 3 simulation operationists who respectfully brought experience from web design, AHA guidelines and JavaScript. We consulted Jonathan Craddock, a colleague within the university who specializes in mobile application development.
Development of the PWA was done using a collection of Bootstrap, HTML5, CSS, JSON and JQuery. PWAs are websites that work as a traditional website but are also progressively enhanced with offline capabilities and cross-platform interoperability to operate like a native app when installed on a mobile device. The CCF PWA was designed for a CPR coach to be able to easily control 2 timers during a code in order to reduce errors, accurately calculate CCF and allow the CPR coach to stay focused on the rate, placement and depth of compressions. A dynamic calculation of CCF is displayed while the two timers are active, and a final CCF is displayed if either one of the timers has been paused. An optional, audible metronome is also available to the CPR coach to hear while the chest compression timer is active. Code duration is displayed to help the CPR coach to keep track of time for transitions, and pulse checks.
Figure 1: Screenshot of the Progressive Web Application. Both of the timers for the Code Time and the Compression Time are marked for easy access. The metronome is at the top and can be toggled on and off for convenience. When the timers are active, the real-time CCF calculation will be displayed at the bottom of the app. QR code included.
Using and trialing the Application
The PWA for monitoring CCF allows for CPR coaches during the team dynamics activity to provide real time CCF during mock codes for ACLS, BLS, and PALS. The application being supported by ubiquitous devices and the ease of use allows for participants to easily install or use the application. The ease of use decreased the amount of instructions and confusion with the two-timer method. Further, the real time feedback provided to the team helps to ensure that interruptions are limited to 10 seconds. The application was tested and used during team dynamics and CPR training during Basic Life Support, Advanced Cardiac Life Support and Pediatric Advanced Life Support Courses taught in our facilities over the last 3 years.
To improve the Application and gather user feedback, a web-based form was developed. This feedback form is accessible through the PWA and asks users about utilization, data accuracy, general impressions as well as gathering demographics of the end user. Users are invited to complete the feedback form at any time. Feedback form submissions are automatically sent to developers via email.
There are limitations to the use of real time CCF as a data point. For example, mathematically the CCF starts at zero and increases after the first few cycles of CPR. Providing feedback of CCF within the first few cycles of CPR might falsely portray the timeliness of CPR. During advanced courses, additional interruptions to CPR pose a threat to the current CCF. However, it has been observed that these interventions do not decrease the CCF below 60% when quality CPR was performed prior to.
An internal, companion application was also developed by the authors to record the historical CCF calculation throughout the code. This historical code consists of 0.1-second interval timestamps along with the real-time calculation of the CCF at that point in time. This historical data can be plotted to observe the evolution of the CCF throughout the entire duration of the code. Figure 2 shows the historical CCF calculation during one complete mock code. In the figure, the times at which various events occurred, such as when compressions are started, compressions are stopped or paused, and when the AED assessed and advised a shocked, are denoted with different colors. During the mock code that was depicted in the figure, the CCF was steadily maintained within the recommended range of 60-80% after about one minute. As expected, the CCF increased while compressions were being performed and it decreased during the times when breaths were given or when the AED assessed and/or advised administering a shock.
Figure 2: Historical evolution of CCF calculations throughout the full duration of a mock code. Red dots indicate when compressions were started. Green dots indicate when compressions were stopped or paused, and breaths were started. Blue dots indicate when the AED assessed the rhythm and/or advised administering a shock. Dotted, horizontal lines denote AHA’s recommended CCF range of 60% to 80%.
Conclusion
Computer-based tools have been developed to replace the use of stopwatches in mock codes. One such tool is a Progressive Web Application (PWA) that calculates CCF using built-in timers in one easy to access interface. The PWA can be used as a guided resuscitation tool to enhance CPR training and teamwork to minimize interruptions and improve the effectiveness of CPR. The tool also provides the functionality of an adjustable metronome. Historical data from the mock code was captured with a companion application. This data was plotted and analyzed for trends.
It is shown that the CCF varies greatly between the first few rounds of CPR, but begins to stabilize afterwards. Over the longer duration of the code, the stabilization will result in the real-time CCF converging to the overall, mean CCF. Thus, we can conclude that the initial calculations of CCF during the first cycle of CPR are not a good indicator of overall participant performance during a mock code.
References
American Heart Association (2018) 2015 Guidelines BLS ILT Course FAQ. https://cpr.heart.org › bls-ilt-faq_updated-11818.
American Heart Association. (2022). Full Code Pro. https://cpr.heart.org/en/cpr-courses-and-kits/healthcare-professional/full-code-pro.
Kleinman, M. E., Brennan, E. E., Goldberger, Z. D., Swor, R. A., Terry, M., Bobrow, B. J., ... & Rea, T. (2015). Part 5: adult basic life support and cardiopulmonary resuscitation quality: 2015 American Heart Association guidelines update for cardiopulmonary resuscitation and emergency cardiovascular care. Circulation, 132(18_suppl_2), S414-S435. DOI: 10.1161/CIR.0000000000000259.
Microsoft (2022). Overview of Progressive Web Apps (PWAs). Microsoft Edge developer documentation. Retrieved from https://docs.microsoft.com/en-us/microsoft-edge/progressive-web-apps-chromium/ on July 22, 2022.