Capnography Versus Carotid Doppler During CPR

 comparison of carotid doppler ultrasonography and capnography in evaluating the efficacy of cardiopulmonary resuscitation: The first study.

The end-tidal carbon dioxide (ETCO2) measurement is accepted as the gold standard method for assessing cardiopulmonary resuscitation (CPR) efficacy.  In this study, the carotid blood flow measurement was compared with ETCO₂ measurement to determine whether this method could be used as an alternative method to capnography in the assessment of CPR efficacy.

This study was conducted on patients who presented at the Emergency Department with non-traumatic arrest or began to suffer from arrest during emergency service follow-up. The main carotid artery peak systolic velocity (PSV), end diastolic velocity (EDV) and time-dependent mean flow velocity (MNV), and ETCO₂ values were measured and recorded after the 100th chest pressure of the CPR cycle and the results were statistically analyzed.

The mean values of patients measured from the carotid artery during the CPR were PSV 67.1±17.3, EDV 16.3±4.5, MNV 25.5±8.1 and ETCO₂22.2±8.1. A significant difference was found between in-hospital and out-of-hospital arrests in terms of patient outcome (return of spontaneous circulation (ROSC) and death) (p<0.05). The mean ETCO₂ values of those who died were found to be lower than those of the ROSC group (p<0.05). Although there was a positive and low-level of correlation between the ETCO2 values and PSV values, and a positive and very low-level of correlation between the EDV and MNV values of all patients, these correlations were not statistically significant. (p>0.05).

A low correlation was found between the PSV and ETCO2 values. With effective CPR, the results close to carotid blood flow in normal healthy individuals were obtained. However, the study showed that carotid blood flow measurement results during CPR were not as valuable as ETCO2 in demonstrating CPR efficacy.

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Three important conclusions can be inferred from this study.

1. As authors point out that capnography is the gold standard of CPR

2. Capnography confirms the tracheal location of endotracheal tube. Correct placement of endotracheal tube is one of the critical prerequisites of successful CPR.

3. Carotid blood flow measurements are not as valuable as capnography data in demonstrating CPR efficacy.