Effects Of Different Positive Pressure Ventilation Methods On The Duration Of Non-hypoxic Apnoea In Obese Patients During Induction Of General Anesthesia

Objective The purpose of this study to compare the effects of 10cm H₂O CPAP,6cm H₂O PEEP,and their combination on the duration of non-hypoxic apnoea in obese patients during laparoscopic vertical（sleeve）gastrectomy.Methods Eighty patients who underwent elective laparoscopic vertical（sleeve）gastrectomy in the People’s Hospital of Inner Mongolia Autonomous Region from December 2021 to December 2022 were selected,Aged from 18 to 45 years,Both sexes,regardless of gender,Elective surgery,BMI>30kg/m²,ASAⅡ～III grade,no severe cardiovascular and pulmonary diseases before surgery,no lung surgery,no respiratory tract infection,no history of claustrophobic syndrome.The patients were randomly divided into four groups（n=20）by random number table method.Group L:Oxygen flow of 6L/min,and mask oxygen was given for 3min,After general anesthesia induced drug administration patients lost consciousness,they were ventilated mechanically with mask for 3 minutes.Group C:10cm H₂O CPAP was applied during 3min of mask oxygen.After that,ventilate the mask mechanically for 3minutes.Group P:PEEP was applied with 6cm H₂O during 3min of mechanical ventilation after 3min of mask oxygen.Group CP:10cm H₂O CPAP during mask oxygen,6cm H₂OPEEP was used during mechanical assisted ventilation with a mask buckle.After entering the operating room,the venous access of the upper extremities was opened,and the radial artery of the upper extremities was punctured and catheterized under local anesthesia.The mean arterial pressure（MAP）,heart rate（HR）,and blood oxygen saturation（Sp O₂）were monitored.All patients were treated with 6L/min oxygen flow,head up at 30°for preoxygenation,and the tidal volume was set at 7ml/kg during mechanical ventilation with mask.During the induction period of general anesthesia,different modes of positive pressure ventilation were used according to the above groups.After the completion of ventilation and endotracheal intubation.After successful intubation,the endotracheal tube was exposed to the air without breathing circuit,and the time from respiratory arrest to Sp O₂decreasing to 90%（the duration of non-hypoxic apnoea）was recorded.Then the respiratory circuit was connected to the lung recruitment maneuver and mechanical ventilation was performed.MAP and HR were recorded after entering the room（T₁）,before intubation（T₂）,after intubation（T₃）and when Sp O₂decreased to 90%（T₄）.Arterial blood samples were collected at T₂and T₄,and blood gas indexes were detected by blood gas analyzer,and arterial partial pressure of oxygen（Pa O₂）and partial pressure of carbon dioxide（Pa CO₂）values were recorded.To evaluate the comfort of patients with positive pressure ventilation during the induction period of general anesthesia and the observation of gastric flatulence during the operation.Results 1.There was no significant difference in gender,age,BMI,ASA grade,preoperative Sp O₂level and hemoglobin content among the four groups（P>0.05）.2.Duration of non-hypoxic apnoea:Compared with group L,the duration of non-hypoxic apnoea in the other three groups was significantly prolonged（P<0.05）.There was no significant difference in the duration of non-hypoxic apnoea between groups C and P（P>0.05）.The duration of non-hypoxic apnoea in group CP was slightly longer than that in group C and group P,but there was no significant difference among the three groups（P>0.05）.3.MAP and HR:MAP at T₁,T₃and T₄in each group was higher than that at T₂,and the difference was statistically significant（P<0.05）.There was no significant difference in MAP between groups at the same time point（P>0.05）.No significant difference in HR between groups at different time points and among groups at the same time point（P>0.05）.4.Pa O₂and Pa CO₂:The Pa O₂at T₂in each group was higher than that at T₄,and the difference was statistically significant（P<0.05）.Pa O₂at T₂in group L was lower than that in the other three groups（P<0.05）.There was no significant difference in Pa O₂at T₄among the three groups（P>0.05）.The Pa CO₂of each group at T₂was lower than that at T₄,and the difference was statistically significant（P<0.05）.There was no significant difference in Pa CO₂between groups at the same time point（P>0.05）.5.There were 8 cases in group C and 6 cases in group CP when using 10cm H₂O CPAP,respectively.There was no obvious gastric flatulence during the operation.Conclusion（1）The application of 10cm H₂O CPAP,6cm H₂O PEEP and their combination during induction of general anesthesia in obese patients can increase oxygen reserve and prolong the duration of non-hypoxic apnoea,and has no significant effect on hemodynamics（2）CPAP combined with PEEP can further prolong the duration of non-hypoxic apnoea,but its effect is limited.（3）CPAP and PEEP have similar effects on the duration of non-hypoxic apnoea in obese patients,but CPAP can cause discomfort to patients.Using PEEP instead of CPAP may be a better positive pressure ventilation method to prolong the duration of non-hypoxic apnoea in obese patients.