传统的肺功能检测仪是基于测量呼气和吸气期间的气流和压力变化来评估受测者的呼吸功能.这些技术主要基于机械式压差传感器或涡轮传感器,通过测量受测者口腔吹气和吸气的能力来评估其肺功能.其所测得的肺功能参数包括峰值呼气流量(peak expiratory flow,PEF)和用力肺活量(forced vital capacity,FVC)等.本文报道了基于动态湿度传感技术发展而来的穿戴式呼吸功能检测系统(穿戴式呼吸波谱仪).基于湿度传感器的特点,对呼吸检测原理与设备的定量设计与模拟潮气实验进行了全面的探索.根据达西定律,通过穿戴式呼吸波谱仪的气体流量与其内外压差成正比关系,该系统符合压差式传感原理.以此为基础,根据其结构特点,建立PEF和FVC与传感器电信号变化的定量关系.实验结果验证了波谱仪内相对湿度的最大变化率与PEF呈线性正相关的关系.波谱仪的模拟潮气实验结果表明,测试范围为180-840 L/min条件下,PEF的示值误差小于 10%,相邻测试误差小于 5%,频率响应测试误差小于 12%,符合呼气峰值流量计行业标准的要求.此外,将传统便携式肺功能检测仪作为对照,进行不同PEF(300-720 L/min)和FVC(3-6 L)条件下的模拟潮气实验.结果表明,波谱仪所测PEF和FVC的平均示值误差分别约为 0.35%和 0.23%,均远远小于便携式肺功能检测仪,充分验证了该系统对肺功能实时评估的准确性和可靠性.更重要的是,在模拟自由呼吸条件(PEF为12-24 L/min,FVC为0.5-0.7 L)下,波谱仪的电信号变化与 自由呼吸体积仍呈线性关系.因此,穿戴式呼吸波谱仪可对人体自然、微弱的鼻呼吸,进行自由、动态、定量的长期监测.所测量人们的自由呼吸波谱在人体肺功能实时监测以及呼吸系统疾病远程监测方面,具有巨大的应用潜力.
Traditional lung function detectors are based on measuring the changes in airflow and pressure during expiration and inspiration to evaluate the respiratory function of the subject.These techniques are mainly based on mechanical differential pressure sensors or turbine sensors which evaluate the lung function of the subject by measuring the ability of the subject to blow and inhale and determine their lung function parameters,including peak expiratory flow(PEF)and forced vital capacity(FVC).In this study,we present a wearable respiratory function testing system called the wearable respiratory spectrometer,which is developed based on dynamic humidity sensing technology.By exploring the principles and quantitative design of respiratory detection and conducting simulations of humidity sensors,we investigate the comprehensive characteristics of the system.According to Darcy's law,the gas flow measured by the wearable respiratory spectrometer is directly proportional to the pressure difference inside and outside the device,showing that the system follows the differential pressure sensing principle.According to this basis and combining the structural characteristics of the system,we establish a quantitative relationship among PEF,FVC,and the changes in sensor electrical signals. The experimental results validate a linear positive correlation between the maximum rate of relative humidity change inside the spectrometer and PEF.Additionally,the results of simulated moisture volume experiments of the spectrometer show that in the measurement range from 180 to 840 L/min,the indication error of PEF is less than 10%,the adjacent test error is less than 5%,and the frequency response test error is less than 12%,which meet the industry standards for peak expiratory flow meters.Moreover,we compare the spectrometer with traditional portable lung function testing devices in simulated moisture volume experiments at different PEFs(300 to 720 L/min)and FVCs(3 to 6 L).The results demonstrate that the average indication error of measured PEF and FVC by the spectrometer are about 0.35%and 0.23%,respectively,both are much lower than those of the portable lung function testing devices,thus fully verifying the accuracy and reliability of this system for real-time lung function assessment.Importantly,under simulated free-breathing conditions(PEF from 12 to 24 L/min,FVC from 0.5 to 0.7 L),the changes in the electrical signals of the spectrometer maintain a linear relationship with the moisture volume.Therefore,the wearable respiratory spectrometer can provide the long-term,free,dynamic,and quantitative monitoring of natural and weak nasal breathing.The measured respiratory spectra of subjects have great potential in real-time monitoring of lung function and remote monitoring of respiratory system diseases.