Hamilton L H, Christman N T, Rickaby D A
J Appl Physiol Respir Environ Exerc Physiol. 1977 Nov;43(5):911-5. doi: 10.1152/jappl.1977.43.5.911.
An acoustic gas analyzer was developed to measure helium during the closing volume (CV) test. It is based on the principle that altering the composition of a gas mixture will change the velocity at which sound is transmitted through the gas. The change in transit time for an acoustic burst across an in-line (breathe-through) cell is measured as a function of He concentration in the expired air during the CV test. Although CO2 and H2O vapor affect the signal, so it is not specific for He, the system provides good records of CV. A comparison of measurements in 21 normal subjects demonstrated no differences for CV measured in the same breath by the bolus technique using the acoustic gas analyzer and by the resident gas method using a nitrogen analyzer. Differences in closing volumes measured by the He bolus technique and the resident gas method might exist in patients with some kinds of pulmonary disease, and the suggestion is made that CV measurements by the two methods might assist in describing pulmonary alterations in patients with bronchopulmonary disease.
开发了一种声学气体分析仪，用于在闭合气量（CV）测试期间测量氦气。它基于这样一个原理：改变气体混合物的成分会改变声音在气体中传播的速度。在CV测试期间，测量穿过在线（通气）池的声脉冲的传播时间变化，作为呼出气体中氦浓度的函数。尽管二氧化碳和水蒸气会影响信号，因此它对氦气不具有特异性，但该系统提供了良好的CV记录。对21名正常受试者的测量结果进行比较表明，使用声学气体分析仪的团注技术和使用氮气分析仪的残留气体法在同一呼吸中测量的CV没有差异。在某些类型的肺部疾病患者中，使用氦团注技术和残留气体法测量的闭合气量可能存在差异，有人提出，这两种方法测量的CV可能有助于描述支气管肺部疾病患者的肺部改变。
