Lutchen K R, Giurdanella C A, Jackson A C
Department of Biomedical Engineering, Boston University, Massachusetts 02215.
J Appl Physiol (1985). 1990 Jun;68(6):2403-12. doi: 10.1152/jappl.1990.68.6.2403.
Respiratory input impedance (Zrs) from 2.5 to 320 Hz displays a high-frequency resonance, the location of which depends on the density of the resident gas in the lungs (J. Appl. Physiol. 67: 2323-2330, 1989). A previously used six-element model has suggested that the resonance is due to alveolar gas compression (Cg) resonating with tissue inertance (Iti). However, the density dependence of the resonance indicates that is associated with the first airway acoustic resonance. The goal of this study was to determine whether unique properties for tissues and airways can be extracted from Zrs data by use of models that incorporate airway acoustic phenomena. We applied several models incorporating airway acoustics to the 2.5- to 320-Hz data from nine healthy adult humans during room air (RA) and 20% He-80% O2 (HeO2) breathing. A model consisting of a single open-ended rigid tube produced a resonance far sharper than that seen in the data. To dampen the resonance features, we used a model of multiple open-ended rigid tubes in parallel. This model fit the data very well for both RA and HeO2 but required fewer and longer tubes with HeO2. Another way to dampen the resonance was to use a single rigid tube terminated with an alveolar-tissue unit. This model also fit the data well, but the alveolar Cg estimates were far smaller than those expected based on the subject's thoracic gas volume. If Cg was fixed based on the thoracic gas volume, a large number of tubes were again required. These results along with additional simulations show that from input Zrs alone one cannot uniquely identify features indigenous to alveolar Cg or to the respiratory tissues.
2.5至320赫兹的呼吸输入阻抗（Zrs）呈现出高频共振，其位置取决于肺内驻留气体的密度（《应用生理学杂志》67: 2323 - 2330, 1989）。先前使用的六元件模型表明，这种共振是由于肺泡气体压缩（Cg）与组织惯性（Iti）发生共振所致。然而，共振的密度依赖性表明它与第一气道声学共振有关。本研究的目的是确定能否通过使用纳入气道声学现象的模型，从Zrs数据中提取组织和气道的独特特性。我们将几种纳入气道声学的模型应用于9名健康成年人在室内空气（RA）和20%氦 - 80%氧（HeO2）呼吸时2.5至320赫兹的数据。一个由单个开口刚性管组成的模型产生的共振比数据中观察到的要尖锐得多。为了减弱共振特征，我们使用了多个平行开口刚性管的模型。该模型对RA和HeO2的数据拟合都非常好，但对于HeO2需要更少且更长的管。另一种减弱共振的方法是使用一个以肺泡 - 组织单元终止的单个刚性管。该模型对数据拟合也很好，但肺泡Cg估计值远小于基于受试者胸内气体体积预期的值。如果根据胸内气体体积固定Cg，则再次需要大量的管。这些结果以及额外的模拟表明，仅从输入Zrs中无法唯一识别肺泡Cg或呼吸组织固有的特征。
