Difference in final concentration of CO2 exhaled (EtCO2) over time compared to the time T0 - 2 5 10 15 20 25 30 35 40 45 50 55 60 >60 SPO2 Nhóm I Nhóm II 5 10 15 20 25 30 35 40 45 50 55 60 >60 ETCO2 Nhóm I Nhóm II Group I Group II Group I Group II 16 Most EtCO2 decreased compared with the time T0 in both groups, however the difference was not statistically significant at most of the time (p>0.05).