Purpose: Near lnfrared spectroscopy enables measurement of cerebral oxygen saturation (rS02), which has been linked to quality of chest compressions and return of spontaneous circulation (ROSC) during cardiopulmonary resuscitation (CPR). The objective of this study was to analyze and compare changes in rS02 and EtC02
levels during chest compression sequences delivered by a mechanical device to out of-hospital cardiac arrest patients (OHCA).
Materials and methods: 11 patients treated by Emergentziak-Osakidetza , the Basque emergency medical system (EMS), were included, 7 had ROSC and 4 did not. Concurrent recordings of rS02 (Nonin, SenSmart) and ECG, impedance and capnography were obtained (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 EtC02, and left (rS02,L) and right (rS02,R) lobe rS02 were measured. The rS02 levels in the last minute after
compressions were also measured to compare ROSC and no-ROSC patients.
Results: On average the oximeter was connected 7.5 (5-13) min after arrival of the EMS, and 49 compression sequences were obtained of average duration 2.1 (1.2) min. The median (1-3 quartile) increase in brain saturation for rS02,L and rS02,R were 3.9 (1.2-9.0) and 3.5 (0.8-7.0) percent points, respectively, giving a per minute increase of 1.9 (0.6-5.6) and 1.9 (0.4-3.9) (see figure). The average increase in EtC02 per sequence was 4.3 (1.7-6.6) mmHg, far a 1.7 (0.7-3.8) mmHg increase per minute. End of episode median (IQR) rS02,L and rS02,R far ROSC/no-ROSC patients were 62.3(18.6)/23.7(26.3)% , and 61.3(15)/46.6(5.9)% , respectively.