Ryan Anne Murphy

Association between Prehospital CPR Quality and End-Tidal Carbon Dioxide Levels in Out-of-Hospital Cardiac Arrest

Abstract Introduction: International Guidelines recommend measurement of end-tidal carbon dioxide (EtCO2) to enhance cardiopulmonary resuscitation (CPR) quality and optimize blood flow during CPR. Numerous factors impact EtCO2 (e.g., ventilation, metabolism, cardiac output), yet few clinical studies have correlated CPR quality and EtCO2 during actual out-of-hospital cardiac arrest (OHCA) resuscitations. The purpose of this study was to describe the association between EtCO2 and CPR quality variables during OHCA. Methods: This is an observational study of prospectively collected CPR quality and capnography data from two EMS agencies participating in a statewide resuscitation quality improvement program. CPR quality and capnography data from adult (≥18 years) cardiac resuscitation attempts (10/2008–06/2013) were collected and analyzed on a minute-by-minute basis using RescueNet™ Code Review. Linear mixed effect models were used to evaluate the association between (log-transformed) EtCO2 level and CPR variables: chest compression (CC) depth, CC rate, CC release velocity (CCRV), ventilation rate. Results: Among the 1217 adult OHCA cases of presumed cardiac etiology, 925 (76.0%) had a monitor-defibrillator file with CPR quality data, of which 296 (32.0%) cases had >1 minute of capnography data during CPR. After capnography quality review, 66 of these cases (22.3%) were excluded due to uninterpretable capnography, resulting in a final study sample of 230 subjects (mean age 68 years; 69.1% male), with a total of 1581 minutes of data. After adjustment for other CPR variables, a 10 mm increase in CC depth was associated with a 4.0% increase in EtCO2 (p < 0.0001), a 10 compression/minute increase in CC rate with a 1.7% increase in EtCO2 (p = 0.02), a 10 mm/second increase in CCRV with a 2.8% increase in EtCO2 (p = 0.03), and a 10 breath/minute increase in ventilation rate with a 17.4% decrease in EtCO2 (p < 0.0001). Conclusion: When controlling for known CPR quality variables, increases in CC depth, CC rate and CCRV were each associated with a statistically significant but clinically modest increase in EtCO2. Given the small effect sizes, the clinical utility of using EtCO2 to guide CPR performance is unclear. Further research is needed to determine the practicality and impact of using real-time EtCO2 to guide CPR delivery in the prehospital environment.

Telephone CPR Instructions in Emergency Dispatch Systems: Qualitative Survey of 911 Call Centers.

Introduction Out-of-hospital cardiac arrest (OHCA) is a leading cause of death. The 2010 American Heart Association Emergency Cardiovascular Care (ECC) Guidelines recognize emergency dispatch as an integral component of emergency medical service response to OHCA and call for all dispatchers to be trained to provide telephone cardiopulmonary resuscitation (T-CPR) pre-arrival instructions. To begin to measure and improve this critical intervention, this study describes a nationwide survey of public safety answering points (PSAPs) focusing on the current practices and resources available to provide T-CPR to callers with the overall goal of improving survival from OHCA. Methods We conducted this survey in 2010, identifying 5,686 PSAPs; 3,555 had valid e-mail addresses and were contacted. Each received a preliminary e-mail announcing the survey, an e-mail with a link to the survey, and up to three follow-up e-mails for non-responders. The survey contained 23 primary questions with sub-questions depending on the response selected. Results Of the 5,686 identified PSAPs in the United States, 3,555 (63%) received the survey, with 1,924/3,555 (54%) responding. Nearly all were public agencies (n=1,888, 98%). Eight hundred seventy-eight (46%) responding agencies reported that they provide no instructions for medical emergencies, and 273 (14%) reported that they are unable to transfer callers to another facility to provide T-CPR. Of the 1,924 respondents, 975 (51%) reported that they provide pre-arrival instructions for OHCA: 67 (3%) provide compression-only CPR instructions, 699 (36%) reported traditional CPR instructions (chest compressions with rescue breathing), 166 (9%) reported some other instructions incorporating ventilations and compressions, and 92 (5%) did not specify the type of instructions provided. A validation follow up showed no substantial difference in the provision of instructions for OHCA by non-responders to the survey. Conclusion This is the first large-scale, nationwide assessment of the practices of PSAPs in the United States regarding T-CPR for OHCA. These data showing that nearly half of the nation’s PSAPs do not provide T-CPR for OHCA, and very few PSAPs provide compression-only instructions, suggest that there is significant potential to improve the implementation of this critical link in the chain of survival for OHCA.