Lutchen K R, Everett J R, Jackson A C
Department of Biomedical Engineering, Boston University, Massachusetts 02215.
J Appl Physiol (1985). 1993 Mar;74(3):1089-99. doi: 10.1152/jappl.1993.74.3.1089.
In humans, application of the DuBois (DuBois et al. J. Appl. Physiol. 8: 587-594, 1956) six-element model to respiratory transfer impedance (Ztr) data has been proposed as a means to noninvasively estimate airway and tissue properties. This approach requires prior knowledge of alveolar gas compressibility (Cg). With input impedance (Zin), prior knowledge of Cg is not required, but the data do not support a reliable separation of airway from tissue properties. In this study, we investigated the separation of airway and tissue properties when Ztr and Zin data are measured and analyzed simultaneously over a larger frequency range than usual. In 10 healthy adults, we measured Ztr and Zin from 2 to 64 Hz. Zin was measured using both the standard approach with oscillations directly into the airway opening (Zst) and the head generator approach (Zhg) with oscillations applied around the head. With Ztr data alone, we found that the airway resistance and inertance estimates were reliable with only 2- to 32-Hz data and were unaffected by including the additional 32- to 64-Hz data. Conversely, the estimates of tissue resistance and inertance were highly unreliable unless the 32- to 64-Hz data are included. Because of enhanced sensitivity of Ztr to Cg from 32 to 64 Hz, inaccuracies in the assigned Cg will distort the estimated tissue but not airway properties. The Ztr-based parameters predicted Zhg data far better than Zst data, which is consistent with Zhg data being less influenced by upper airway shunting over this frequency range. There was no apparent advantage to combining Ztr and Zhg data during parameter estimation. With Cg unfixed, the estimated Cg was 50-100% higher than expected from an independent measurement of functional residual capacity. These results confirm that Ztr alone can provide a reliable distinction of lumped respiratory airway and tissue properties that are little influenced by upper airway wall shunting but only if 2- to 64-Hz data are analyzed. This distinction, however, requires an accurate prior measurement of Cg, and this requirement cannot be removed by combining Ztr and Zin data.
在人类中，有人提出将杜波依斯（杜波依斯等人，《应用生理学杂志》8: 587 - 594, 1956）的六元件模型应用于呼吸传递阻抗（Ztr）数据，作为一种无创估计气道和组织特性的方法。这种方法需要肺泡气体压缩性（Cg）的先验知识。对于输入阻抗（Zin），则不需要Cg的先验知识，但这些数据并不支持可靠地将气道特性与组织特性分离。在本研究中，我们调查了在比通常更大的频率范围内同时测量和分析Ztr和Zin数据时，气道和组织特性的分离情况。在10名健康成年人中，我们测量了2至64赫兹的Ztr和Zin。使用直接向气道开口施加振荡的标准方法（Zst）和在头部周围施加振荡的头部发生器方法（Zhg）来测量Zin。仅使用Ztr数据时，我们发现仅2至32赫兹的数据就能可靠地估计气道阻力和惯性，并且包含额外的32至64赫兹数据并不会对其产生影响。相反，除非包含32至64赫兹的数据，否则组织阻力和惯性的估计非常不可靠。由于Ztr在32至64赫兹对Cg的敏感性增强，指定Cg的不准确将扭曲估计的组织特性，但不会影响气道特性。基于Ztr的参数对Zhg数据的预测远优于Zst数据，这与在该频率范围内Zhg数据受上呼吸道分流影响较小一致。在参数估计过程中，组合Ztr和Zhg数据没有明显优势。在Cg未确定的情况下，估计的Cg比通过功能残气量的独立测量预期的值高50 - 100%。这些结果证实，仅Ztr就能可靠地区分集总的呼吸道和组织特性，这些特性受上呼吸道壁分流的影响很小，但前提是要分析2至64赫兹的数据。然而，这种区分需要对Cg进行准确的先验测量，并且通过组合Ztr和Zin数据并不能消除这一要求。
