ABSTRACT
Objective To determine the optimal pressure for facemask ventilation during induction of general anesthesia by real-time ultrasonographic measurement of antral cross-sectional area (CSA) in adult patients.Methods Sixty American Society of Anesthesiologists physical status Ⅰ or Ⅱ patients,aged 18-60 yr,with body mass index of 20-25 kg/m2,scheduled for elective operation under general anesthesia,were divided into 5 groups (n=12 each) using a random number table:P10 group,P13 group,P16 group,P19 group and P22 group.After induction of anesthesia,an oropharyngeal airway was inserted,and the patients were ventilated for a 2-min period in a pressure-controlled mode using the two-handed mask ventilation technique.The pressure for facemask ventilation was 10,13,16,19 and 22 cmH2O in P10,P13,P16,P19 and P22 groups,respectively.The antral CSA was measured using real-time ultrasonography before and after facemask ventilation.Respiratory parameters were recorded.Results Compared with group P1O,the number of patients in whom CSA＜340 mm2 after facemask ventilation was significantly decreased in P16,P19 and P22 groups,and the number of patients in whom the tidal volume ≥ 6 ml/kg was increased in P13,P16,P19 and P22 groups (P＜ 0.01).The number of patients in whom optimnal pressure for facemask ventilation was achieved was 2,10,6,4 and 1 in P10,P13,P16,P19 and P22 groups,respectively,with the most cases in group P13 (P ＜ 0.01).Conclusion The optimal pressure is 13 emH2O for facemask ventilation during induction of general anesthesia when determined by realtime ultrasonographic measurement of antral CSA,and it can ensure adequate oxygen supply and reduce gastric insufflation in adult patients.