Effects Of Differentairway Pressures On Pu’monary Atelectasis After General Anesthesia In Lung Recruitment

Objective:To observe the effect of different airway pressures on pulmonary atelectasis after general anesthesia in lung recruitment technology based on lung ultrasonography.Methods:90 patients from The Second Affiliated Hospital of Soochow University,scheduled to undergo thyroidectomy from Dec.2017 to Mar.2018,were randomly divided into three groups(30 cases in each group)by using the random number table.Group Ⅰ(control group),volume controlled ventilation,tidal volume 8ml/kg,I:E is 1:2,PEEP:0cmH2O,without pulmonary reopening;In group Ⅱ,the ventilation setting was the same as that in the control group,pulmonary reopening was performed every 30min after anesthesia and before extubation,and the reopening pressure was 30cmH2O.The difference between groupⅢand group Ⅱ was that the retension pressure was set to 40cmH2O.When the lung is inflation,the model of volume controlled ventilation(VCV)was changed to Hand-controlled ventilation mode,which can make the pressure reach the set value quickly.Then the lung recruitment was conducted in 30 seconds.All the patients were given the same Anesthesia induction,Anesthesia maintenance,airway management,hemodynamic management,fluid management,Postoperative analgesia and the same vital signsmonitoring method.Ultrasound observation time point:Pre-operation(T0),post-operation PACU(Ti),and 20h to 30h after post-operation(T2).The location of ultrasound examination:the two lungs were divided into anterior area,lateral area and posterior area longitudinally by bilateral parasternal line,axillary front line,posterior axillary line and paravertebral line,and divided into upper lung area and lower lung area horizontally according to the level of the fourth intercostal space of the midline of clavicle,which were divided into 12 regions.Based on the LUS evaluation criteria,the corresponding evaluation LUS score of each zone can be get,and the total LUS score of the lungs,the scores of different zones at the same time,and the scores of the same zone at different time can be obtained.Results:(1)There was no statistically significant difference in the difference of the total LUS scores among the three groups of patients at the time point T0(p>0.05).Compared the total LUS scores between T1 and T2,the score of Group I was higher than that of Group Ⅱ and Group Ⅲ,and the score of Group II was higher than that of Group III.The difference was statistically significant(p<0.05;(2)Among the three groups of patients,the total LUS score of the same group of patients at time point T1 was higher than that at the time point T0 and T2.The total LUS score at T2 was higher than that at T0.And the difference was statistically significant(p<0.05);(3)The total LUS scores of the bilateral posterior upper lung region and posterior lower lung region were higher than other regions,and the score of posterior lower lung region was higher than that of posterior upper lung region.The difference was statistically significant(p<0.05);(4)The mean arterial pressure(MAP)and the heart rate(HR)of the Group Ⅱ and Group III were decreased during the lung inflation.Compared with the difference before the lung inflation,the decrease of MAP was statistically significant(p<0.05),but the decrease of HR was no statistically significant(p>0.05).After the lung inflation,the MAP and HR can reach the original level quickly.Conclusion:According to the results in this study:the pulmonary ultrasonography images of the patient with thyroidectomy were changed in different degrees after general anesthesia,especially in bilateral back.It will last for more than 1 day after surgery,and has the tendency to decrease.During the procedure of mechanical ventilation,the degree of changes in the pulmonary ultrasonography images of the patients can be deceased by using the Hand-controlled lung inflation lung recruitment method;In this study,the performance with the pressure of lung inflation 40cm H2O is better than that of 30cmH2O;During the procedure of the lung inflation,the pressure will make a short impact on the hemodynamics of patients.After the lung inflation,it will return the original level quickly.