Comparison Of Two Techniques Of Preoxygenation In Adults

Purpose: To discuss two preoxygenation techniques, spontaneous breathing 3 minutes before induction and face-mask with manual-controlled ventilation after induction, with respect to the effectiveness and safeness of induction method of general anesthesia.Methods: Forty adult patients undergoing elective surgery, ASA Ⅰ-Ⅱ,aged 25-55, BMI(Body Mass Index)<28kg/m2, were randomly allocated to two groups, Group C was classic face-mask ventilation group, Group S was spontaneous breathing group. All the patients received remifentanil, propofol and vecuronium for induction, Group C was injected before ventilation, Group S was injected after preoxygenation. Each patients’ datas should be recorded:HR,blood pressure, minute ventilation, Pa O2, Pa CO2, p H, the volume of gastric insufflation after preoxygenation, the duration of Sp O2 fell from 100% to 95%,90% onset the apnea.Result: Distribution of age, height, weight and BMI were comparable in two groups. Baseline HR, blood pressure, Pa O2, Pa CO2, p H of two groups were comparable. After preoxygenation Group S had a significantly high Pa O2 value than Group C(448.38±42.75 mm Hg vs. 293.37±35.72 mm Hg). At 90% desaturation there was no significant difference between groups. Group S showed a significantly high apnea desaturation time when compared to Group C(Sp O2 fell to 95%: 444.41±46.68 s vs. 239.53±28.32 s; Sp O2 fell to 90%: 490.57±47.91 s vs. 308.53±26.60 s).The average minute ventilation in Group C and Group S were 5.20±0.56 L/min, 5.70±1.21 L/min, respectively.The volumn of gastric insufflation was observed with a statistically significant larger in Group C than in Group S(247.50±85.21 ml vs. 65.75±14.95 ml).Conclusion: A marked degree of gastric insufflation was observed in Group C, and the period of Sp O2 fell from 100% to 95%, 90% were shorter in Group C. The study indicated that spontaneous breathing before induction was safer than face-mask ventilation. Spontaneous breathing ventilation would appear to be a better airway management than the face-mask ventilation.