| The depth of anesthesia depends on the plasma concentrations of the anaesthetic,so online measuring of anesthetic concentrations is important for anaesthetists to ensure the safety of patients.Propofol is an intravenous anaesthetic that accounts for about 70%market share in clinical surgery.However,a clinically useful method for measuring propofol anaesthesia levels is still not available.Fortunately,it has been confirmed that propofol can be detected in exhaled breath,and the exhaled propofol concentrations are well related to that in plasma.This provides a theoretical basis for real-time monitoring of propofol anaesthesia.In this study,an on-line clinical exhaled propofol monitoring method based on miniaturized linear ion trap mass spectrometer was proposed.And a miniaturized linear ion trap instrument was developed,with the specially design of instrument structure,control methods and data processing modules.The performance of the designed instrument was tested,demonstrating the feasibility of the proposed method.The main works are completed as follows:Firstly,on the basis of theoretical research,the system design scheme was determined.According to the characteristics that exhale gas with complex composition,large background interference,low propofol concentrations and high boiling point during anesthesia,the exhaled gas sample system and mass spectrometer were designed and optimized.Including:developed a new interface based on PDMS semi-permeable membrane;designed a high-temperature EI source with antioxidant filament;designed a high-stability RF power module based on constant temperature technology.These key modules and the application of key technologies ensure that the miniaturized mass spectrometer has low detection limit,high stability and anti-interference ability,and the capability for real-time monitoring of propofol anesthetics in exhaled gas.Secondly,a specific-software for the online mass spectrometry instrument was completed.Mainly including:realized a high-speed and stability data transmission module based on TCP/IP protocol;synthesized SWIFT signal for ion selective excitation;designed software modules of mass calibration,data smoothing,peak recognition and ion extraction;realized an intelligent human-computer interaction interface based on the ZedGraph control;enabled one-click operation combined with related control flow algorithms,.Finally,experiments were carried out to investigate the capability of the instrument for propofol measurement.In the first set of experiments,the performance of the instrument was evaluated,using standard samples of propofol that in the same concentration level as the exhaled gas of anesthetized patients.The animal experiment was developed to investigate the relation between the relative changes of propofol concentration detected on-line by the instrument and the behavior of mice during anesthesia.In the third sequence of experiments,a pre-clinical experiment was carried out,and the exhaled air sample from an anaesthetized patient was detected offline to demonstrate the propofol detection capability of the instrument.The results show that the dedicated miniaturized online mass spectrometer has a unit mass resolution,a detection limit of ppb level,and the stability error(RSD)is less than 10.3%.Propofol can be detected in the breath of the anesthetize patient.At present,the instrument is in the stage of principle prototype development.Because of problems such as qualification licensing and medical safety certification,it has not yet entered the real clinical experiment stage.However,previous experiments have shown that the miniaturized propofol online mass spectrometry system proposed in this study is highly feasible for clinical propofol online monitoring in exhaled breath.It provides a convenient,noninvasive method to follow the propofol concentration in plasma simultaneously,which has high medical value and application prospects. |
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