| The precise control of anesthetic doses is particularly important to ensure the smooth operation of the procedure and the safety of patients during surgeries.Currently,limited to the strict requirement of instrument size and analysis rate in clinical environment,methods for non-invasive,online,continuous and accurate detecting of anesthetics are still rare.In this regards,the development of portable monitoring equipment based on new technical means would benefit to the anesthetic dosage control and ensure the safety of patients.On the other hand,with the proposal of concept"Breath Biopsy",breath testing attracted more and more attention in the field of disease auxiliary diagnosis and drug concentration monitoring.Of note,as a non-invasive,online and continuous analytical method,breath testing also has a high potential in the applications of anesthesia monitoring.In this thesis,a gas chromatography-surface acoustic wave sensor combined(GCSAW)system was proposed,which attained the demands of the portability and analysis rate for on-line breath monitoring in clinical practice.Furthermore,we ultilized the GCSAW system to detect the concentrations of anesthetics,and realized a simultaneous,non-invasive,online and continuous monitoring of sevoflurane and propofol in patient’s exhaled gas.On this basis,the linear correlation between blood/exhaled gas concentrations of the i.v.propofol was verified,and the effects of different breathing patterns on the blood/exhaled gas distribution coefficient of propofol(RBE)were further assessed.Finally,this thesis validated the correlation between the breath concentrations of the two anesthetics and the anesthesia depth of patients.A 3D dose-response model was built to characterize the relationship between the two drug concentrations and the Bispectral index(BIS).In general,this thesis promotes a further application of breath testing technology in the monitoring of anesthetic concentrations,and provides new ideas and technical means for non-invasive and online anesthesia monitoring in clinical practice.The main innovative works of this thesis are clarified in the following aspects:1.Compared to traditional gas chromatograph,the self-built GC-SAW system reduced the instrument size and accelerate the analytical rate,which falicates a non-invasive,on-line and continuous monitoring of patient’s exhaled gas in clinical practice.In the current work,a gas chromatography-surface acoustic wave sensor combined system was built,which realized a quantitative and qualitative analysis of mixed gas components.The direct resistive-heating system for capillary column was designed to reduce the analytical cycle time to 80 seconds.Moreover,a Tenax? TA adsorption tube was employed for the gas pre-concentration.When coupled with the surface acoustic wave(SAW)sensor,the GC-SAW system can achieve a detection limit of ppb level.In addition,the instrument was assembled in modules,and the whole size was compressed to 20*20*35 cm.Finally,the hardware and software were designed for the convenient and automatic operation of the system as well.2.Simultaneous monitoring of the breath concentration of propofol and sevoflurane was achieved through the innovative application of GC-SAW system.In“balance anesthesia”,propofol and sevoflurane are often used in combination.This study innovatively applied the GC-SAW system to monitor the breath concentrations of the two drugs in clinical.In the calibration experiment of sevoflurane,the R2 value between the detection results of the GC-SAW system and GC-MS reached 0.9925.In the clinical experiments,the concentration of sevoflurane monitored by the GC-SAW system was in line with the commercial anesthesia machine.Furthermore,the trends of breath concentrations of the two drugs was matched with the clinical drug usage.Therefore,the self-built GC-SAW system can be used for the simultaneous,noninvasive and online monitoring of propofol and sevoflurane in patient’s exhaled gas.3.The linear correlation between the blood/exhaled gas concentration of i.v.propofol was verified,and the effects of different breathing patterns on the blood/exhaled gas distribution coefficient of propofol(RBE)was first explored.The anesthetic effect of propofol mainly depends on the drug concentration in blood.This thesis first validated the linear correlation between the blood/exhaled gas concentration of propofol.Then a significant negative correlation between minute ventilation(VM)and RBE was found in 46 samples.Moreover,a modified RBE was proposed that was not interfered by the value of VM.Considering the little variation of RBEM in the study group,we assumed the value of RBEM to be a constant in humans.On this basis,a model was built for the prediction of propofol concentration in blood from breath monitoring.4.The association was evaluated between the breath concentrations of anesthetics and the anesthesia depth of patients when propofol and sevoflurane were used in combination.This thesis assessed the association between the breath concentration of the two drugs and the depth of anesthesia,which was characterized by the value of BIS index.In a single patient,the drug concentrations matched the trend of BIS index.Moreover,in the partial correlation analysis in 15 patients,both propofol and sevoflurane showed a significant negative correlation to the BIS index.On this basis,a 3D dose-response model was built,and fitted by 356 sets of data monitored from the 15 patients.The coefficient of determination(COD)value of the model reached 0.985,demonstrating the technical feasibility of monitoring the depth of anesthesia from breath testing. |
