Costantino M L, Fiore G B
Dipartimento di Bioingegneria, Politecnico di Milano, Piazza Leonardo da Vinci, 32, 20133 Milan, Italy.
Med Eng Phys. 2001 Sep;23(7):457-71. doi: 10.1016/s1350-4533(01)00072-8.
Tidal liquid ventilation (TLV) with perfluorocarbons (PFC) has been proposed to treat surfactant-deficient lungs of preterm neonates, since it may prevent pulmonary instability by abating saccular surface tension. With a previous model describing gas exchange, we showed that ventilator settings are crucial for CO(2) scavenging during neonatal TLV. The present work is focused on some mechanical aspects of neonatal TLV that were hardly studied, i.e. the distribution of mechanical loads in the lungs, which is expected to differ substantially from gas ventilation. A new computational model is presented, describing pulmonary PFC hydrodynamics, where viscous losses, kinetic energy changes and lung compliance are accounted for. The model was implemented in a software package (LVMech) aimed at calculating pressures (and approximately estimate shear stresses) within the bronchial tree at different ventilator regimes. Simulations were run taking the previous model's outcomes into account. Results show that the pressure decrease due to high saccular compliance may compensate for the increased pressure drops due to PFC viscosity, and keep airway pressure low. Saccules are exposed to pressures remarkably different from those at the airway opening; during expiration negative pressures, which may cause airway collapse, are moderate and appear in the upper airways only. Delivering the fluid with a slightly smoothed square flow wave is convenient with respect to a sine wave. The use of LVMech allows to familiarize with LV treatment management taking the lungs' mechanical load into account, consistently with a proper respiratory support.
有人提出使用全氟化碳（PFC）进行潮式液体通气（TLV）来治疗早产儿表面活性物质缺乏的肺部，因为它可能通过降低肺泡表面张力来预防肺部不稳定。利用之前描述气体交换的模型，我们表明在新生儿TLV期间，呼吸机设置对于二氧化碳清除至关重要。目前的工作聚焦于新生儿TLV中一些几乎未被研究的力学方面，即肺部机械负荷的分布，预计其与气体通气有很大不同。本文提出了一个新的计算模型，描述肺部PFC流体动力学，其中考虑了粘性损失、动能变化和肺顺应性。该模型在一个软件包（LVMech）中实现，旨在计算不同呼吸机模式下支气管树内的压力（并大致估计剪切应力）。模拟运行时考虑了之前模型的结果。结果表明，由于肺泡高顺应性导致的压力降低可能补偿因PFC粘度增加而导致的压力降增加，并保持气道压力较低。肺泡所承受的压力与气道开口处的压力明显不同；在呼气期间，可能导致气道塌陷的负压适中，且仅出现在上气道。相对于正弦波，以稍微平滑的方波输送液体更方便。使用LVMech可以在考虑肺部机械负荷的情况下熟悉LV治疗管理，这与适当的呼吸支持相一致。
