Value Of Oxygen Reverse Time In Early Screening Of Lung Injury In Patients Undergoing General Anesthesia

objective:To investigate the correlation between different oxygen partial pressure and oxygen reserve time in patients undergoing general anesthesia,to explore the application value of oxygen reserve time in early screening of intraoperative lung injury in patients undergoing general anesthesia,and to provide a reference for early detection and implementation of lung protective ventilation measures in clinical work.Methods:Mechanical ventilation with general anesthesia was performed in our hospital from June 2021 to November 2022.Inclusion criteria:According to Surgical Lung Injury Prediction（SLIP）,high-risk groups with postoperative hypoxemia were included,including thoracic surgery,preoperative chronic obstructive ventilatory dysfunction（COPD）,vascular surgery,and sepsis patients.Patients with head and maxillofacial surgery that could not be operated,intraoperative pure oxygen ventilation percutaneous peripheral oxygen saturation（Sp O₂）could not be maintained above 97%,and spontaneous breathing was restored during the measurement period and affected Sp O₂measurement were also excluded.At the completion of the primary surgery,arterial blood gas analysis was performed to record（PaO₂）,standardized open suctioning procedures were performed,and the time taken for Sp O₂to decrease from 100%to 96%was observed and recorded,which we defined as oxygen reserve time.Postoperative hypoxemia was defined as Sp O₂≤92%after removal of the endotracheal tube in the Postanesthesia care unit（PACU）and Oxygenation Index（OI=PaO₂/Fi O₂）≤300 mm Hg after admission to the Intensive Care Unit（ICU）.Patient age,gender,BMI,preoperative Sp O₂（%）,intraoperative PaO₂（mm Hg）,P/F,oxygen reserve time（ORT,s）,and total PACU time were recorded.The correlation between oxygen reserve time and arterial partial pressure of oxygen was calculated,and the corresponding linear regression equation was obtained.The intraoperative OI of patients was analyzed again,and the patients were divided into two groups:moderate acute respiratory failure syndrome group（Moderate Group,Group M）and severe respiratory failure syndrome group（Severe Group,Group S）.The clinical value of ORT in screening different degrees of lung injury was analyzed.At the same time,whether intraoperative oxygen reserve time could predict the occurrence of postoperative hypoxemia was observed.The receiver operating characteristic curve was drawn,the area under the curve was calculated,and the clinical application value of oxygen reserve time in the early detection and screening of intraoperative lung injury in patients undergoing mechanical ventilation under general anesthesia was evaluated.Results:（1）A total of 85 patients were included,including 56 cases of hypoxemia after general anesthesia.（2）ASA（P=0.001）,age（P=0.037）,and BMI（P=0.015）were higher in the intraoperative lung injury group than in the group without lung injury;however,Sp O₂（%）（P=0.001）,oxygen reserve time（P=0.000）,and intraoperative partial pressure of oxygen（mm Hg）（P=0.000）were lower in the preoperative calm inhalation of air than in the group without lung injury.There was no statistically significant difference in other general patient characteristics data;（3）Spearman correlation analysis evaluated the correlation between oxygen reserve time（ORT）and arterial blood partial pressure of oxygen（PaO₂）,and there was a positive correlation between ORT and PaO₂.There was a strong linear relationship between ORT and PaO₂（R²=0.8535,P<0.0001）.And the linear regression equation was obtained:PaO₂=1.137 ORT+44.35.According to the latest study,ORT was 225 s（sensitivity 95.1%,specificity 97.3%）when PaO₂was 300 mm Hg and 94 s（sensitivity 80%,specificity 30.3%）when PaO₂was 150 mm Hg.（4）There were significant differences in ASA（P=0.002）,age（P=0.013）,BMI（P=0.005）,Sp O₂（%）（P=0.000）,oxygen reserve time（QRT,s）（P=0.000）,and intraoperative partial pressure of oxygen（mm Hg）（P=0.000）between the postoperative hypoxic and non-hypoxic groups.ORT was independently associated with postoperative hypoxemia after adjusting for variables.It was lower than that in the group without hypoxemia after surgery.There was no significant difference in gender,height,weight,length of surgery,and mean arterial pressure at admission between the two groups.（5）.The area under the ROC curve was 0.907（95%CI:0.803–0.978）with a sensitivity of 82.1%and a specificity of 93.1%when ORT of 224.5 s was used as a criterion to predict the occurrence of hypoxemia after surgery.Conclusion:There is a positive correlation between ORT and PaO_2.ORT has important clinical value in early screening of intraoperative lung injury in patients undergoing general anesthesia.Preoperative ASA,age,Sp O₂and ORT in patients undergoing general anesthesia are associated with postoperative hypoxemia.