Research On The Detection Method Of Lung Diffusion Function And Its Design And Implementation

In recent years,the incidence rate of chronic respiratory diseases represented by Chronic Obstructive Pulmonary Disease(COPD)has remained high,which has become a public health problem seriously endangering national health.As the main method for evaluating pulmonary ventilation function,pulmonary diffusion function test is an indispensable and vital part of a pulmonary function test,and it is also an essential method to comprehensively evaluate the human lung function status.It plays an important role in locating the sites of the lesion,diagnosis of disease type,evaluating diseases status.The domestic research on lung diffusion function detection technology started late,and there is no full-fledged independent product,which makes the pulmonary diffusion function detection instruments used by various medical units remain heavily reliant on imports.Imported instruments are complicated to operate,expensive,expensive to maintain,which makes them difficult to popularize.Therefore,this dissertation conducts in-depth research on the detection method of pulmonary diffusion function and designs a platform for detection of pulmonary diffusion function with simple operation and reliable performance.The specific research contents are as follows:(1)Analysis of Principle and Method of Pulmonary Diffusion Function TestThe principle and theoretical calculation model of pulmonary diffusion function detection were expounded,and we have made a comparison and analysis with the mainstream test methods and test gases.We proposed a pulmonary diffusion function test method based on single-breath method and the design scheme of the testing platform,also analyzed the main error sources,including respiratory airflow measurement errors and gas concentration analysis sensor delays.(2)Design of Pulmonary Diffusion Function Testing PlatformFirstly,in order to standardize the implementation of the breath test,a breathing path based on a large-diameter,low-resistance mechanical switch valve,and a test path based on a breathing regulator were designed,respectively,to realize the two tests conditions of low-resistance breathing and safe inhalation of test gas;Secondly,the gas analysis module and its calibration channel were designed based on the micro quick reversing valve,and the dead space volume of the equipment was reduced by partial gas circuit reuse(<200mL),and the system gas circuit structure was simplified;Thirdly,given the mutual exclusion of respiratory air flow detection accuracy and range requirements,a flow acquisition module based on a low-resistance throttling device and a dual differential pressure sensor group is designed to realize high-precision measurement of respiratory air volume signals;Then,according to the requirement of high-fidelity sampling of the concentration signal of breathing gas components,we respectively designed the air pressure signal acquisition circuit based on high-precision absolute pressure sensor,the high-resolution driving current source based on DAC,and the driving circuit for air pump based on PWM.Thus,we realized the effective controls of the air pressure acquisition suction pipe,proportional valve,and air pump.Furthermore,the front/rear dual PID controller is constructed based on the incremental PID algorithm to realize the constant speed air pumping function;Finally,aiming at the estimation error of dead space volume in the process of VA index extraction,based on the Fowler method,by designing a dead space volume measurement model and a dead space volume acquisition algorithm,direct measurement of dead space volume is realized.Combined with multi-channel signal acquisition and index extraction methods,we finalized VA and DLCO acquisition.(3)Verification of Key Modules and Complete Machine of Pulmonary Diffusion Detection PlatformA corresponding test platform was built to verify that the volume measurement accuracy of the flow acquisition module meets the requirements(when using a 3L calibration cylinder,the result is less than ±75mL),and the constant-speed pumping function of the gas analysis module is realized(the fluctuation of the air flow rate at the bleed line is less than ±5mL/min),whose measurement accuracy is less than±1%.Through index comparison experiment,we compared the instruments with imported instruments of the same type,and the results showed that there was no significant difference between the two(P>0.5),and a high correlation(correlation coefficient>0.8)was observed,thus the effectiveness of the detection platform is verified.