Purpose: Measures of capnography and cerebral oximetry have been linked to quality of chest compressions and return of spontaneous circulation (ROSC) during cardiopulmonary resuscitation (CPR). Near infrared spectroscopy enables measurement of cerebral oxygen saturation (rSO2). This study compared rSO2 and EtCO2 during mechanical CPR and evaluated their power to predict ROSC in out-of-hospital cardiac arrest patients (OHCA).
Materials and methods: Emergentziak-Osakidetza, the Basque emergency medical system (EMS), concurrently recorded rSO2 (Nonin, SenSmart), and ECG, impedance and capnography Lifepak 15, Physio-Control). Chest compressions were delivered using the LUCAS-3 device (Physio-Control). Compression sequences longer than 30 s were analyzed, and the change in EtCO2, and left (rSO2,L) and right (rSO2,R) lobe rSO2 were automatically computed by signal processing. The rSO2 and EtCO2 levels one minute after the last compression were compared for ROSC/no-ROSC patients.
Results: 57 patients (46 male) with mean(std) age 68(12) years were included, and oximetry was recorded 9.2(4.1) min after arrival of the EMS. A set of 232 compression sequences (see Figure) were obtained with average duration of 2.1(1.0) min. The median(1-3 quartile) increase of brain saturation per patient, rSO2,L and rSO2,R, were 1.8(1.0-5.7) and 1.5(0.5-2.8) percent points, an increase of 1.1(0.7-2.6)  and 0.8(0.2-1.5) points per minute. The average increase in EtCO2 was 1.4(0-4.1) mmHg per sequence and 0.7(0-2.1) mmHg per minute. 
ROSC was observed in 25 patients at the end of the recording. The rSO2,L and rSO2,R for ROSC/no-ROSC patients were 61.0(48.7-75.6)/39.6(25.8-47.6)%, and 62.6(51.0-78.3)/45.0(32.7-54.8)%, respectively (p<0.001). EtCO2 values were 27.0(14.1-37.7) and 14.0(5.7-22.7) mmHg for ROSC and no-ROSC patients (p>0.01).
Conclusions: Capnography and cerebral oximetry in both frontal lobes increased during mechanical CPR. Brain saturation was significantly higher in ROSC patients. 
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7 - Cerebral oximetry vs capnography to monitor chest compressions and return of spontaneous circulation in out-of-hospital cardiac arrest