SCCM Resource Library-Pediatric Chest Compression Duty Cycle Using Arterial Pressure Waveforms

Video Transcription

Hello everybody, my name is Tommy Rapphold. I am a critical care medicine fellow at the Children's Hospital of Philadelphia, and today I'm going to be talking about pediatric chest  compression duty cycle using arterial pressure waveforms. First, what is duty cycle? And for  the remainder of the talk, I'll interchangeably refer to it as DC. Duty cycle is the proportion  of time spent in the compression phase of an entire CPR cycle. Preclinical studies support that a DC greater than 50% is deleterious, leading to decreased myocardial blood flow  in return of spontaneous circulation. Current CPR guidelines recommend a duty cycle of 50%  where the time spent in compression and decompression is equal. Preclinical studies support a duty  cycle less than 50%. Dean et al. showed that shorter duty cycles are associated with higher cerebral and coronary perfusion pressures. Swart and colleagues showed that shorter  duty cycle is associated with higher mean arterial and coronary perfusion pressures. And Kim et al. showed that shorter duty cycle is associated with higher systolic and diastolic  blood pressures that increase over time. There is limited clinical studies that have looked  at duty cycle and only one by Wolfe and colleagues that examined duty cycle in pediatrics where  they found shorter duty cycle is associated with decreased rate. In adults, Johnson and colleagues found that shorter duty cycle is associated with increased depth and decreased  rate. Our duty cycle study was an analysis of prospectively collected data from a multicenter interventional trial using the ICU recess database. This database included patients  who experienced in-hospital cardiac arrest between October 1, 2016 and March 31, 2021. We included patients from 37 weeks gestational age to 18 years of age who underwent CPR in  an ICU setting. Data was prospectively collected in the ICU recess database. All CPR data was  collected from the Zoll R-series defibrillator models. And duty cycle calculations were done with a novel arterial line waveform method that I will discuss.  Initially, based on our preclinical data and the duty cycle distribution of our data, we defined three duty cycle targets, less than 30%, 30-35%, and greater than 35%. Our outcome  variables were hemodynamic measurements during cardiac arrest, systolic and diastolic blood  pressure. We also explored clinical outcomes, return of spontaneous circulation, and survival  with and without good neurological outcomes. Next, I want to explain how we used intra-arrest arterial waveforms to calculate duty cycle. On the screen is a force waveform similar  in shape to those generated by chest compression force transducers in our preclinical lab during  CPR. The peak of the wave represents the end of a compression, while the wave's descent represents the chest recoil. From a previously described and validated method, the area duty  cycle is calculated as the ratio between the area under the force curve, in dark blue, and the total area of one rectangle, in red, outlining the compression-decompression curve.  This is termed the area duty cycle, or ADC. We decided to apply the area duty cycle method  to an aortic pressure waveform in the preclinical setting, and what we noticed was the aortic  area duty cycle approximated the force area duty cycle closely. This is graphically represented  here with three preclinical subjects. And in the lower right corner, comparative statistics in these animals show a small difference in the mean across the subjects.  On the screen now is an example arterial waveform from a human subject in our study. Zeroing  in on one single wave, and applying the same waveform analysis as used in the aortic pressure  waveform, we were able to calculate duty cycle using the area under the pressure curve, highlighted  in dark blue, and the total area of one rectangle, highlighting a CPR cycle, in light blue. With this method, we derived the following aims. One, develop a method to calculate duty  cycle using arterial line waveforms. Two, describe the landscape of duty cycle during pediatric resuscitation across a multicenter network. Three, determine if there was an  association between duty cycle and intra-arrest goals. And four, we wanted to investigate the association between duty cycle and clinical outcomes.  Here are our study cohort characteristics. Age and the diagnosis of sepsis and congenital heart disease prior to CPR were significantly different across the three groups.  These are the CPR event characteristics. There were no significant differences across the three exposure categories. And these are the remaining CPR event characteristics. Again,  none of which had significant differences across the duty cycle groups. To start our results, the duty cycle over the entire cohort had a normal looking distribution.  The mean duty cycle was 32.5. On the screen now is our univariate analysis of intra-arrest outcomes for the entire cohort.  The statistical test treats the values from each group as ordinal values, as there appears  to be trends when looking at the means across each group. Here we found an association between  duty cycle and systolic blood pressure, where patients with shorter duty cycles had higher  systolic blood pressures. We also saw an association between duty cycle and chest compression, although it was not significant.  On the screen is our univariate analysis of intra-arrest outcomes for patients greater than or equal to 1 and those less than 1. For the former, we see a similar trend with  significance in systolic blood pressure and chest compression rates as it was for the entire cohort. For those less than 1, there is a significant association between systolic  blood pressure and duty cycle. For our univariate analysis of duty cycle and clinical outcomes, we did not find a statistically  significant association. Secondary analysis using spline and ROC curves indicated that a duty cycle of 33% may be an ideal target. Also, we thought a duty cycle of 33% may be  a teachable skill in high-quality CPR. Therefore, we decided to run multivariable models looking at intra-arrest and clinical  outcomes where the primary predictor was a duty cycle of less than 33%. These models controlled for age, vasopressor support at time of arrest, and respiratory decompensation  as an immediate cause of arrest. We found that systolic blood pressure was significantly higher by 13 points in those patients who received duty cycle of less than a third.  None of our clinical outcomes were significantly associated with a duty cycle of 33%. It was exciting to see that shorter duty cycles are associated with higher systolic  blood pressures. Physiologically, this made sense for two reasons. First, a shorter duty  cycle allows for longer filling time and greater end-diastolic volume. And second, this increased  volume and flow is directly proportional to pressure when resistance is held constant. Duty cycle is not associated with diastolic blood pressure clinically. We also thought  this made sense as a longer relaxation phase will allow for more diastolic runoff, leading to either lower or unchanged diastolic blood pressure. In the entire cohort univariate  analysis, we saw a signal of shorter duty cycles are associated with slower chest compression  rates. This same trend was observed by Wolff and colleagues in previous work. In neither a univariate nor a multivariate analysis did we find an association with duty cycle in  clinical outcomes. For the multivariate analysis we controlled for factors we thought would  influence chest dynamics and thus duty cycle, such as age, respiratory disease, and vasopressor  score at time of compressions. The lack of outcome association speaks likely to the multitude  of patient factors that contribute to outcomes. Our limitations include, first, this was a retrospective study where we can only look at associations between duty cycle exposure  and outcomes. Second, although our novel method closely measures duty cycle with previously described methods using force waveforms, we recognize that we are not exactly measuring  duty cycle. There are other factors that influence the blood pressure waveform from which we  are measuring. However, by calculating duty cycle from the arterial waveform, we may have  a new CPR performance measurement that incorporates CPR mechanics with patient physiology. In  conclusion, this retrospective review demonstrates that shorter duty cycles are associated with  higher systolic blood pressures in a multivariable model without significantly impacting other  hemodynamic outcomes or CPR mechanics. This result is consistent with preclinical data. For our next steps, we plan to use our arterial waveform algorithm to calculate duty cycle  in real time during CPR. If a CPR team chooses, this may be incorporated into goal-directed CPR coaching. In addition to my wonderful co-authors listed on the title slide, this  project had many contributors listed here as well. Thank you all for your time. I'd now like to answer any questions.

Video Summary

The video discusses the concept of duty cycle in pediatric chest compressions during CPR. Duty cycle refers to the proportion of time spent in the compression phase of CPR. Preclinical studies have shown that a duty cycle greater than 50% is harmful, leading to decreased blood flow. The current guidelines recommend a duty cycle of 50%, but there is limited clinical data on this topic. The study analyzed data from a multicenter trial using arterial pressure waveforms to calculate duty cycle. The results showed that shorter duty cycles were associated with higher systolic blood pressures, but did not significantly affect other outcomes or CPR mechanics. The study suggests that shorter duty cycles may be beneficial in pediatric CPR.

Asset Subtitle

Resuscitation, Cardiovascular, Pediatrics, 2022

Asset Caption

INTRODUCTION/HYPOTHESIS: Chest compression duty cycle (DC) remains understudied in pediatric cardiopulmonary resuscitation (CPR) and can be calculated by dividing the area under the force curve by the total area of one compression–decompression (area duty cycle [ADC]). In our pilot laboratory testing, there was high concordance between force-determined ADC and invasive arterial blood pressure (ABP) waveform-determined ADC. Our objective was to utilize this novel ADC method to 1) quantitatively describe DC during pediatric in-hospital CPR and 2) evaluate its association with intra-arrest hemodynamics and patient outcomes. METHODS: Subjects included children ≤18 years old and ≥37 weeks corrected gestational age who received chest compressions while admitted to one of the 18 participating intensive care units of The ICU-RESUScitation Project (NCT028374497). In this convenience sample, ADC was calculated as the ratio between the area under the invasive ABP waveform and the total area of the compression cycle (base of area calculation = line at compression cycle diastolic BP [DBP]). American Heart Association (AHA) DC guideline compliance was defined as an average event DC of 50 ± 5%. Percentage of events compliant with AHA DC was compared to an a priori hypothesized compliance percentage of 10% using Chi-square test. Differences across DC quartiles for intra-arrest BPs were analyzed by Kruskal-Wallis test and outcomes by Chi-square test. RESULTS: Among 160 patients, median [IQR] age was 2.9 [0.12, 3.1] years; during CPR systolic BP (SBP) 81.9 [61.6, 111.3] mmHg; DBP 43.0 [33.5, 54.7] mmHg. Return of spontaneous circulation occurred in 112 (70%) with survival to discharge in 96 (60%). ADC quartiles were: Q1 (≤30.6%), Q2 ( >30.6–35.1%), Q3 ( >35.1–38.2%), Q4 ( >38.2%). Only 5 (3.1%) events met AHA DC compliance, significantly less than the a priori hypothesis of 10% (p CONCLUSIONS: Using a novel method of ADC calculated from the ABP waveform, DC during pediatric ICU CPR is rarely compliant with AHA recommendations. The SBP differed across ADC quartiles; however, DBP and outcomes were similar.

Meta Tag

Content Type Presentation

Knowledge Area Resuscitation

Knowledge Area Cardiovascular

Knowledge Area Pediatrics

Knowledge Level Advanced

Membership Level Select

Tag Cardiopulmonary Resuscitation CPR

Tag Hemodynamic Monitoring

Tag Pediatrics

Tag Cardiac Arrest

Tag Outcomes Research

Tag Cardiothoracic Critical Care

Year 2022

Keywords

duty cycle

pediatric chest compressions

CPR

blood flow

systolic blood pressures

	Society of Critical Care Medicine 500 Midway Drive Mount Prospect, IL 60056 USA Phone: +1 847 827-6888 Fax: +1 847 439-7226 Email: support@sccm.org	Contact Us About SCCM Newsroom Advertising & Sponsorship DONATE	MySCCM LearnICU Patients & Families Surviving Sepsis Campaign Critical Care Societies Collaborative	GET OUR NEWSLETTER
© Society of Critical Care Medicine. All rights reserved. \| Privacy Statement \| Terms & Conditions The Society of Critical Care Medicine, SCCM, and Critical Care Congress are registered trademarks of the Society of Critical Care Medicine.