Effect Of Apneic Oxygen Insufflation(AOI) Combined With Lower Inhaled Oxygen Concentration On Lung Injury In Elderly Patients During One-lung Ventilation

Objective:Discussing the possible lung protective effect of apneic oxygen insufflation（AOI）combined with low fraction of inspired oxygen on patients with one lung ventilation（OLV）and emphatically comparing the effects on hypoxemia,oxygenation index,intrapulmonary shunt and postoperative pulmonary complications during OLV in patients undergoing endoscopic radical resection of esophageal cancer so as to provide theoretical basis for clinical patients with one lung ventilation to choose more optimized ventilation strategy.Method:120 patients with elective ASAI-III grade total endoscopic radical resection of esophageal cancer were recruited,aged 65-85 years old,of any sex,with body mass index（BMI）of 19-28kg/m².All the included patients did not suffer from systemic or respiratory infection diseases before operation,and there was no severe abnormality in the functions of heart,lung,brain and other important organs before operation.Preoperative pulmonary function examination showed that the first second forced expiratory volume/forced vital capacity（FEV1/FVC）was>0.8,and the patients with esophageal cancer did not receive radiotherapy,chemotherapy and other tumor-related treatments before operation,and did not smoke or quit smoking for more than 4 weeks before operation.They were randomly divided into 4 groups（n=30）:Group C（control group,30 cases with FiO₂（fraction of inspired oxygen）=100%during OLV）;Group A（30 cases with FiO₂（fraction of inspired oxygen）=100%during OLV+AOI）;Group D（30 cases with FiO₂（fraction of inspired oxygen）=60%during OLV）;Group A+D（30 cases with FiO₂（fraction of inspired oxygen）=60%during OLV+AOI）.No drugs were used before anesthesia for each group.The same anesthetic medication and operation plan were adopted,and the operation was performed by the surgeons of the same group and the same operation plan was adopted.FiO₂=100%was used for rapid induction anesthesia in each group of patients,and all patients received left one lung ventilation.During double lungs ventilation,FiO₂=100%was adopted.The tidal volume（TV）was set at 6-8ml/kg,the corrected body weight,and the Positive End-Expiratory Pressure（PEEP）was 3-5cm H₂O.Before one lung ventilation,the fiberoptic bronchoscope confirmed that the catheter was located correctly and there was no secretion blocking the airway.During one lung ventilation,the oxygen concentration was changed to the target fraction of inspired oxygen（FiO₂）,and TV was set to 5ml/kg,the corrected body weight,PEEP5cm H₂O.The expiratory ratio of the residual respiratory parameters was set to 1:1.5,the respiratory rate（RR）was 14-18times/min,and the end-tidal carbon dioxide(P_ETCO₂)was adjusted to 35-45mm Hg as appropriate.During one lung ventilation of group A and group A+D,the non-ventilate side lung was continuously given 5L/min of oxygen.When the patient was in OLV,the SpO₂dropped below 90%（ECG monitor data）and lasted for more than 1min.The case was recorded and eliminated.The hypoxic ventilation group was immediately provided with the pure oxygen ventilation and double lung ventilation was implemented when necessary.Observation indicators:（1）Satisfaction evaluation of non-ventilated side lung collapse quality and operative visual field exposure effect.（2）Occurrence of hypoxemia during OLV:Pulse oxygen saturation（SpO₂）was continuously monitored during the operation,the number of cases in which SpO₂decreased to 90%during OLV in each group was recorded,the incidence rate of hypoxemia during OLV in each group was calculated,and the cases were eliminated.（3）Blood gas analysis and oxidative stress related indicators:Radial artery blood and venous blood from the internal jugular vein near the right atrium were taken for blood gas analysis for 4 groups of patients at 1min（T₁）before one lung ventilation,60min（T₂）after one lung ventilation and 30min（T₃）after one lung ventilation,the oxygenation index（OI）and intrapulmonary shunt（Qs/Qt）were calculated;.（4）Postoperative pulmonary complications and recovery:and the total hospital stay after operation.Results:21 cases were included in group C,23 cases were included in group A,20cases were included in group D,and 24 cases were included group A+D.Finally,88patients were included in the study.（1）Incidence rate of hypoxemia during OLV:For incidence rate of hypoxemia,group D was significantly higher than groups C,A and A+D（P<0.05）;groups A and A+D was significantly lower than in group C（P<0.05）;and comparison of difference between groups A and A+D was not statistically significant（P>0.05）.（2）Comparison of satisfaction with lung collapse and effect of operative visual field exposure:During OLV,comparison of difference of the satisfaction of lung collapse and the effect of visual field exposure of patients in groups C,A,D and A+D was not statistically significant（P>0.05）;（3）Blood gas analysis indicators:（1）Lactate:Comparison of difference between patients in groups C,A,D and A+D at the same time point was not statistically significant（P>0.05）.The lactic acid value of each group was within the normal range（<2.5mmol/L）.（2）Oxygenation index:Compared with T₁,PaO₂/FiO₂ of patients in groups C,A,D and groups A+D at T₂ decreased（P<0.05）,and compared with T₂,PaO₂/FiO₂ of patients in groups C,A,D and A+D at T₃ increased（P<0.05）.At T₂,PaO₂/FiO₂in group A and group A+D was significantly higher than that in group C and group D（P<0.05）;PaO₂/FiO₂of patients in group D was slightly lower than that of patients in group C,but there was no statistical difference（P>0.05）.At T3 time point,comparison of difference of PaO₂/FiO₂between groups C,A,D and A+D was not statistically significant（P>0.05）.（3）Intrapulmonary shunt（Qs/Qt）:Compared with T₁,the Qs/Qt of patients in groups C,A,D and A+D increased significantly at T₂and T₃（P<0.05）,and the Qs/Qt at T₃was significantly lower than that at T₂（P<0.05）.At T₁,comparison of difference of patients in groups C,A,D and A+D was not statistically significant（P>0.05）.At T₂and T₃,Qs/Qt of patients in groups A and A+D was significantly lower than that of patients in group C（P<0.05）,but comparison of difference between groups D and C was not statistically significant（P>0.05）.（4）Postoperative recovery indicators:（1）Postoperative incision infection rate:Comparison of difference of between groups C,A,D and A+D was not statistically significant（P>0.05）.（2）Postoperative incidence rate of patchy infiltration on chest CT:Compared with group C:the incidence rate of patchy infiltration on chest CT in groups D and A+D was significantly lower（P<0.05）.（3）Postoperative chest CT revealed the incidence rate of atelectasis:Compared with group C:The incidence of atelectasis on chest CT in groups D,A+D was significantly decreased（P<0.05）.（4）Postoperative hospital stay:Comparison of differences in groups A,D and A+D was not statistically significant（P>0.05）.（5）Three days after operation,the clinical pulmonary infection score（CPIS）:compared with group C:the postoperative pulmonary infection score of group D and group A+D was significantly lower（P<0.05）Conclusion:1.Reducing the concentration of inhaled oxygen can reduce the incidence of postoperative complications such as atelectasis and pulmonary infection in elderly patients,but the incidence of hypoxemia during OLV increases when inhaled oxygen concentration is reduced alone.2.AOI strategy combined with low inhaled oxygen concentration can improve intrapulmonary shunt and increase pulmonary oxygenation during OLV in elderly patients,reduce the occurrence of hypoxemia during OLV to a certain extent,and reduce the incidence of postoperative atelectasis,pulmonary infection and other pulmonary-related complications.