The Investigation Of The Optimal Combination Of Mechanical Ventilatory Parameters Under General Anesthesia In Obese Patients Undergoing Laparoscopic Adrenalectomy

Objective:The obese patients are susceptible to pulmonary dysfunction after laparoscopic surgery. To reduce or avoid this complication caused by improper combination of mechanical ventilatory parameters, we conducted the following trial of 3 factors with 3 levels of mechanical ventilation in order to let obese patients under general anesthesia obtain the best lung protective effect by low airway pressure with good ventilation.Methods:we choosed repeat orthogonal experimental design of 3 factors with 3 levels. screened 27 ASAⅠ～Ⅱobese patients undergoing selective laparoscopic adrenalectomy as sample cases. Patients were randomly allocated into 9 groups(k=3, n=27)according to the "BMI≧28kg/m2" obesity index(ASAI-Ⅱ). Anesthesia machine parameters were set as follows:respiratory frequency (f), tidal volume (VT), respiratory ratio (I:E)as the three factors of A, B, C, with 3 levels of f=16,13, 10(bpm),VT=8,10,12(mL/kg), I:E=1:2.5,1:2.0,1:1.5. By using L9(34)K=3 repeat orthogonal experimental design and analysis table, the variable factors that affect the respiratory index such as the end tidal carbon dioxide pressure(PetCO2), peak airway pressure (Ppeak), mean airway pressure (Pmean) were analyzed.Results In this study,27 cases undergoing laparoscopic surgery under general anesthesia were allocated into 9 experimental groups. The hemodynamics of these patients was stable, SPO2 was kept at 100 percent during the operation except that a patient with pheochromocytoma suffered fluctuation of blood pressure. The results of different combinations were described as follows:①PetCO2:f and VT with different level had great impact on PetCO2(P<0.01), I:E had no significant difference in three levels(P>0.05);②Ppeak:f had great effect on Ppeak(P<0.05); VT and I:E in three levels also had significant effect on Ppeak(P<0.01);③Pmean:all the ventilation parameters with different combination had significant effect on Pmean (P<0.01).Conclusions:The optimal combination of respiratory parameters under general anesthesia in obese patients undergoing laparoscopic adrenalectomy is f=10bpm, VT=8 mL/kg, and I:E=1:2.0, which can maintain satisfactory mechanical ventilation.In order to let obese patients under general anesthesia obtain the best lung protective effect by low airway pressure with good ventilation, it is worth noting that:①I:E has a great effect on airway pressure(Ppeak, Pmean), which is important for lung protection;①I:E has the opposite effect on Ppeak and Pmean...