Fig. 1
Consort diagram. 998 parturients who were planned for elective cesarean section in Quanzhou Women’s and Children’s Hospital were screened between May 2013 and July 2014. Inclusion criteria: singleton pregnancy, aged 18 to 50 years old, ASA 2, and fasted for at least 6 h. Parturients with potentially difficult airway, known reflux disease, or with BMI ≥ 35 kg/m2 were excluded. 49 parturients refused consent, and 29 did not meet the recruitment criteria. The remaining 920 parturients were randomized by opaque envelope to obtain 460 in each group. There were no dropouts or withdrawal