Jackson A C, Neff K M, Dorkin H L, Lutchen K R
Department of Biomedical Engineering, Boston University, MA 02215, USA.
Pediatr Pulmonol. 1996 Dec;22(6):364-75. doi: 10.1002/(SICI)1099-0496(199612)22:6<364::AID-PPUL5>3.0.CO;2-J.
Respiratory input impedance (Zin) is a potentially informative test of pulmonary function in infants who are unable to perform standard tests commonly performed in children and adults Analysis of Zin in dogs using the six-element model of DuBois et al. (J Appl Physiol 8:587, 1956) provides estimates of airways resistance separate from tissue resistance, as well as an estimate of thoracic gas volume. However, reliable estimates of these parameters can only be obtained when Zin displays a distinct antiresonance that is associated with the tissue inertance and alveolar gas compression compliance. To determine whether infants have such an antiresonance. Zin was measured in nine healthy infants (4 < f < 160 Hz). An antiresonance was found at 112.8-10.4 Hz, and the six-element model fit these data well, but the resulting parameters were physiologically unrealistic. We hypothesized that the antiresonance in the measured Zin is the result of shunt compliance proximal to alveolar gas compression compliance. Gas compression in the face mask and nonrigid upper airway walls could provide such a shunt compliance. We investigated another model with four parameters, a single shunt compliance (Cim) representing gas compression in the face mask in parallel with the infant's total respiratory resistance (Rrs) inertance (Irs), and compliance (Crs). This model fits the data well, and the estimated R, (19.3, 4.2 cmH O/L/s) was physiologically reasonable. However, Crs (Crs 1.03-0.58 mL cmH2O) was one order of magnitude smaller than reported Crs. The value for Cim was slightly larger than that based on the estimated volume of gas in the face mask, suggesting an additional influence of upper airway wall shunting. Computer simulations using a model that includes the face mask and upper airway walls confirmed that Cim and the upper airway wall properties significantly influence Zin data over this frequency range. Nevertheless, these simulations suggest that the Rrs estimated from the four-element model is related to airway resistance.
呼吸输入阻抗（Zin）对于无法进行儿童和成人常用标准测试的婴儿来说，是一种潜在的肺功能信息测试。使用DuBois等人（《应用生理学杂志》8:587，1956）的六元件模型对犬的Zin进行分析，可以分别估算气道阻力和组织阻力，以及胸廓气体容积。然而，只有当Zin表现出与组织惯性和肺泡气体压缩顺应性相关联的明显反共振时，才能获得这些参数的可靠估算值。为了确定婴儿是否存在这种反共振，对9名健康婴儿（4<f<160 Hz）进行了Zin测量。在112.8 - 10.4 Hz处发现了反共振，六元件模型对这些数据拟合良好，但所得参数在生理上不现实。我们推测，测量的Zin中的反共振是肺泡气体压缩顺应性近端分流顺应性的结果。面罩和非刚性上呼吸道壁中的气体压缩可提供这种分流顺应性。我们研究了另一个具有四个参数的模型，一个单一的分流顺应性（Cim）代表面罩中的气体压缩，与婴儿的总呼吸阻力（Rrs）、惯性（Irs）和顺应性（Crs）并联。该模型对数据拟合良好，估算的Rrs（19.3，4.2 cmH₂O/L/s）在生理上是合理的。然而，Crs（Crs 1.03 - 0.58 mL/cmH₂O）比报道的Crs小一个数量级。Cim的值略大于基于面罩中气体估计体积的值，表明上呼吸道壁分流有额外影响。使用包含面罩和上呼吸道壁的模型进行的计算机模拟证实，Cim和上呼吸道壁特性在此频率范围内对Zin数据有显著影响。尽管如此，这些模拟表明从四元件模型估算的Rrs与气道阻力有关。
