Development of a device for pulmonary mechanics testing in children

为评价肺力学，研制了儿童压力型人体体积描记仪和计算机信号处理程序。肺内气与肺外气之间的频率特性在实际应用中是相同的，可以用胸腔体积V_1(T)到呼吸气体体积V_2(T)的体积透过率来分析肺力学。肺系统透过率是用一个呼吸周期内体积信号的各傅立叶分量的幅值和相角来测量的。正常人的幅值和相角在0-5赫兹的频率范围内是恒定的。其幅值随频率的增加而减小，5赫兹后相位最高可达90。透过率的频率特性随呼吸阻力的存在而变化，与呼吸模式的形式无关。这种变化对检测气道阻力比比气道电导更敏感。可以说，这种方法对呼吸道疾病的诊断和治疗等临床应用是有用的。

The pressure-type bodyplethysmography for children and the computer programs for signal processing are developed for the evaluation of pulmonary mechanics. The frequency characteristics betwwen the inside gas and the outside gas of the lung can be regarded as same to practical application and makes it possible to analyze pulmonary mechanics as a volume transmittance from the chest volume V_1(t) to the respiratory gas volume V_2(t).The transmittance of the pulmonary system is measured as magnitude and phase angle of each Fourier's component of the volume signals in one respiratory cycle. The values of amplitude and phase angle are constant within the frequency range of about 0-5 Hz in normal subjects. The magnitude decreases with an increase of the frequency and phase rotates upto 90 after 5 Hz. The frequency characteristics of transmittance changes with an presence of penumatic resistance and is independent from the form of breathing pattern. This change is more sensitive to detect the airway resistance than specific airway conductance. It can be said that this method is useful to clinical application such as the diagnosis and the treatment of the airway diseases.