Abstract 20338: Differential Correlation of ETCO2 and CPR Quality Between Out-of-Hospital Arrests of Cardiac and Respiratory Etiology
Introduction: While modest correlation between end-tidal CO2 (ETCO2) and CPR quality has been reported among patients who have arrested from presumed cardiac etiology, it is unknown whether this correlation exists in arrests of respiratory etiology. We compared the correlation between ETCO2 and CPR quality among these two groups.
Methods: ETCO2 was monitored with side-stream CO2 (Philips/Respironics or Oridion) and CPR quality with an accelerometer-based system (E/X Series, ZOLL Medical) during treatment of consecutive adult (age 18+) OHCA patients with presumed cardiac or respiratory etiology by two EMS agencies in Arizona (10/2008-6/2015). Minute-by-minute ETCO2 and CPR quality data were extracted. Linear mixed effect models were fitted to use (log transformed) ETCO2 level to predict four CPR variables: chest compression (CC) depth, (log) CC rate, CC release velocity (CCRV), and (log) ventilation rate (VR). An interaction term was used to test for differential correlation between the 2 groups. A random intercept for each case was included and a spatial power covariance structure assumed for measurements over time.
Results: A total of 399 subjects (median age: 68 yrs, 63% male, 374 cardiac etiology, 25 respiratory) with 2812 minutes of data were studied. ETCO2 was correlated with CC rate for respiratory etiology (p = .011) but not for cardiac etiology and the difference was marginally significant (p = .085). ETCO2 was correlated with VR for cardiac etiology (p < .0001) but not for respiratory etiology (p = .009 for the difference between etiologies). Doubling ETCO2 was associated with an increase of 8.7mm/s (95% CI: 3.9, 13.5) in CCRV for cardiac etiology and 12.1mm/s (95% CI: -1.8, 26) for respiratory etiology but the difference between etiologies was not significant. Correlation between ETCO2 and CC depth was similar between the 2 groups. In both cohorts, ETCO2 explained <10% of the variance in each CPR variable.
Conclusion: Correlations between ETCO2 and certain CPR variables were different for patients with cardiac vs respiratory etiology. ETCO2 may not be an adequate substitute for CPR quality monitoring in either situation. Future studies are needed to determine how ETCO2 and CPR quality monitoring can be used in combination to optimize CPR.
Author Disclosures: C. Hu: None. D. Spaite: Research Grant; Significant; Medtronic. A. Silver: Employment; Significant; Zoll Medical Corporation. J. Gaither: None. R. McDannold: None. M. Mullins: None. T. Vadeboncoeur: None. B. Bobrow: Research Grant; Significant; Medtronic.
- © 2016 by American Heart Association, Inc.