Abstract 83: High Incidence of Chest Compression Oscillations Associated With Capnography During Out-of-Hospital Cardiopulmonary Resuscitation
Background: Capnography is commonly used to guide ventilation in out-of-hospital (OOH) cardiopulmonary resuscitation (CPR). Advantages of continuous capnography include verification of airway placement, prevention of hyper- or hypoventilation, and identification of airway dislodgement. Chest compressions sometimes produce high frequency waveforms that are superimposed on the much lower frequency respiratory capnogram waveform, but this has not been studied systematically. Chest compression oscillations may be caused by gas moving in and out of the airway during compression/decompression phases of CPR. A few studies reported that chest compressions produce tidal volumes that are less than physiological dead space.
Objective: To assess the proportion of capnograms with chest compression oscillations recorded during OOH CPR.
Methods: We collected electronic recordings made with the Philips HeartSmart MRx monitor-defibrillator during OOH CPR in 210 patients with sudden cardiac arrest (CA) from 2008 to 2010 in two states — Oregon&Texas (OR n=181&TX n=29). Each file included in the study had continuous capnogram waveforms and chest compressions recorded simultaneously with an accelerometer. The record lengths vary from a few seconds to 40 minutes. Two blinded investigators independently reviewed each file and noted those that demonstrated chest compression oscillations.
Results: Chest compression oscillations superimposed on the respiratory capnogram were noted in 154 of 210 (73.3%) files. Rates of chest compression oscillations were usually the same as chest compression rate and often exceeded 100/min. (Figure: bottom strip is the ventilation capnogram, top strip is accelerometer recording of chest compressions)
Conclusions: Chest compression induced oscillations occur frequently on capnography during CPR. Studies measuring tidal volume and blood gases during CPR will clarify if chest compression oscillations contribute to ventilation.
- © 2010 by American Heart Association, Inc.