Abstract 268: Testing ETCO2 as an Indicator of Improved Blood Flow During Prolonged CPR
Introduction: There is renewed interest in end-tidal carbon dioxide (ETCO2) as a metric of chest compression (CC) quality. A detailed study of ETCO2 changes and alterations in blood flow and pressures during CPR has not been performed.
Methods: CPR hemodynamics in three domestic swine (~30 Kg) were studied using standard physiological monitoring. Flow probes were placed on the abdominal aorta, the inferior vena cava (IVC), the right renal artery and vein, the right common carotid and external jugular. Ventricular fibrillation (VF) was electrically induced. Mechanical CC were started after ten minutes of untreated VF. 54 min of CC were delivered at a rate of 100 per minute and at a depth of 1.25 in, which was followed by 6 min of 2 in CC.
Data are presented at the beginning of chest compressions (CC), after 20 minutes of CC at 1.25 inches, after 48 minutes of 1.25 in CC, and after 6 minutes of 2 inch CC. Paired t-tests were used to determine statistical significance.
Results: CPR effectiveness decayed over time (see table) despite continued CC. After increasing CC depth to 2 inches, minimal changes in blood flow and pressure were observed with the exception of a trend in increased net forward flow in the IVC. ETCO2 was significantly increased after increasing chest compression depth and did not change in accordance with changes in net forward aortic blood flow (r=-0.213). ETCO2 correlated most with CC depth (r = 0.557), was weakly correlated with IVC flow (r = 0.332).
Conclusions: Blood volume shifts due to prolonged sub-par CC are difficult to repair. After prolonged CC, ETCO2 correlates more with CC depth than with venous return. ETCO2 may not be a reliable metric of CC generated forward flow.
- © 2012 by American Heart Association, Inc.