Capnographic Monitoring For Eearly Warning Of Hypoxia During Painless Gastrointestinal Endoscopy In Obese Patients

Background and objectiveBy measuring the concentration of end-tidal carbon dioxide,capnographic monitoring can early detect abnormal ventilation or apnea in non-intubation patients undergoing procedural sedation and analgesia,and provides an early warning of the occurrence of hypoxia.Compared with patients with normal body mass index,obese patients have increased the incidence of hypoxia during painless gastrointestinal endoscopy due to their own obesity factors,anesthesia factors and endoscopic operation factors.At present,there is no unified conclusion on whether capnographic monitoring can effectively reduce the incidence of hypoxia during painless gastrointestinal endoscopy,and there is still a lack of research on obese patients who are more prone to hypoxia.The primary objective of this randomized controlled study was to investigate whether an intervention based on capnographic monitoring reduces the incidence of intraoperative hypoxia in obese patients undergoing painless gastrointestinal endoscopy under propofol-combined sufentanil sedation.MethodsThis is a prospective,single-blind,parallel-assignment,randomized,controlled clinical trial.From November 2021 to July 2022,228 obese patients(Body Mass Index,BMI≥ 28 kg/m2)who underwent painless gastrointestinal examination at Qilu Hospital of Shandong University were screened,3 patients withdrew informed consent after randomization,and finally were randomly assigned to 112 obese patients in the experimental group and 113 obese patients in the control group.Standard cardiopulmonary monitoring equipment was used in both groups,and additional capnographic monitoring was performed in the experimental group.When alveolar hypoventilation(defined as altered ventilation,apnea,and/or decreased oxygen saturation)occurred during intravenous anesthesia,interventions such as increasing oxygen flow(≤5L/min),lifting the jaw,placing nasopharynx airway,artificial mask positive pressure ventilation,endotracheal intubation were performed to improve oxygenation.Demographic,clinical and surgical characteristics of the patients in both groups were recorded,including gender,age,BMI,ASA class,history of smoking,history of alcohol consumption,Mallampati Class classification,thyromental distance<6cm,micrognathia or retrognathia,STOP-BANG questionnaire score≥ 3;type of surgery,procedure time,induction propofol dosage(mg/kg),induction sufentanil dosage(ug),total propofol(mg),polypectomy and baseline heart rate,systolic blood pressure,SpO2.The incidence of intraoperative hypoxia(SpO2<90%for≥10s),subclinical respiratory depression(90%≤SpO2<95%)and severe hypoxia(SpO2≤85%),the means of the last intervention to ensure that all respiratory-related indicators returned to normal,the content of anesthesia sedation-related adverse events that occurred in the patients,the measures taken and the outcome of the adverse events,and the postoperative patient and endoscopist satisfaction scores were recorded for both groups.Statistical analysis was performed using SPSS(version 25.0).The measurement data that conformed to a normal distribution is expressed as mean ± standard deviation(x±s)and compared between groups using independent samples t-test.If the measurement data that did not conform to a normal distribution,the data is expressed as median(interquartile range)[M(IQR)],and the comparison between data groups was performed using the Mann-Whitney U test.The enumeration data were expressed as frequencies(%)and compared using the chi-square or Fisher’s exact probability method.Post hoc subgroup analyses for the primary outcome were assessed with the use of logistic regression models.Exploratory analyses in subgroups were sex,age,ASA physical status classification,body mass index,history of smoking,history of alcohol consumption,STOP-BANG questionnaire score,Mallampati Class,thyromental distance<6cm,micrognathia or retrognathia,type of procedure,procedure time.The results show the odds ratio(OR)and 95%confidence intervals for the effect of additional capnography on hypoxia in each subgroup.Statistical significance was set at P<0.05.Results1、Baseline Data:There was no significant difference in baseline demographic,clinical and surgical characteristics between the two groups(P>0.05),such as gender,age,BMI,ASA class,history of smoking,history of alcohol consumption,Mallampati Class classification,thyromental distance<6cm,micrognathia or retrognathia,STOP-BANG questionnaire score≥3;type of surgery,procedure time,induction propofol dosage(mg/kg),induction sufentanil dosage(ug),total propofol(mg),polypectomy and baseline heart rate,systolic blood pressure,SpO2.2、Primary study outcome:Compared with obese patients receiving standard monitoring,the incidence of hypoxemia in patients receiving end-tidal carbon dioxide monitoring was significantly reduced(13.2%vs 30.7%,P<0.001).The incidence of severe hypoxia was significantly lower in the experimental group(5.4%vs 14.2%,P=0.026).3、Secondary study outcomes:The incidence of subclinical respiratory depression was higher in the experimental group than in the control group(30.4%vs.17.7%,P=0.026).The means of the last intraoperative intervention was statistically significant between the two groups(P<0.001).There was no statistically significant difference in intraoperative minimum SpO2,patient and endoscopist satisfaction between the two groups.4、The adverse events of anesthesia sedation and the interventions taken were not statistically significant between the two groups(P>0.05).ConclusionDuring painless gastrointestinal endoscopy under propofol-combined sufentanil anesthesia,capnographic monitoring can detect apnea and altered respiratory patterns in obese patients earlier than SpO2 decreases.Effective interventions given to patients within this time lag can reduce the incidence of hypoxia and severe hypoxia in patients and keep SpO2 in the subclinical respiratory depression stage in most patients.