Revisiting high-frequency oscillatory ventilation in vitro and in silico in neonatal conductive airways.
Revisiting high-frequency oscillatory ventilation in vitro and in silico in neonatal conductive airways.
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DOI：
10.1016/j.clinbiomech.2017.11.009
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发表时间：
2019-06
期刊：
影响因子：
--
通讯作者：
Sznitman J
中科院分区：
文献类型：
--
作者：
Bauer K;Nof E;Sznitman J
高频振荡通气常用于患有呼吸窘迫综合征的早产儿的肺支持。尽管其在新生儿重症监护病房中广泛使用，但迄今为止还没有可接受的用于选择适当通气参数设置的协议。在这种情况下，基本的质量传输机制仍然没有完全理解。我们重新审视的问题，在传统的机械通气和高频振荡通气的新生儿传导气道的解剖启发模型跨越前几代气道的流动现象。我们首先在真实的规模在体外进行粒子图像测速呼吸流模式的测量。接下来，我们通过实施示踪剂boli的拉格朗日跟踪来探索计算流体动力学模拟中的计算机对流质量输运，其中，对流流速是固定的。粒子图像测速测量在八个代表性的呼吸周期的相位角揭示了类似的流动模式，在峰值速度和减速阶段的常规机械通气和高频振荡通气。特性差异发生在加速和流动逆转阶段。净位移的示踪粒子迅速达到渐进的行为超过累积呼吸周期，并建议潮气量和对流质量输送之间的线性关系。观察到的线性关系表明，传统的机械通气和高频振荡通气条件之间的流动特性的差异并没有实质上影响对流传质机制。因此，较低的潮气量不能通过选择较高的频率来直接补偿以保持类似的通气效率。
High frequency oscillatory ventilation is often used for lung support in premature neonates suffering from respiratory distress syndrome. Despite its broad use in neonatal intensive care units there are to date no accepted protocols for the choice of appropriate ventilation parameter settings. In this context, the underlying mass transport mechanisms are still not fully understood. We revisit the question of flow phenomena under conventional mechanical ventilation and high frequency oscillatory ventilation in an anatomically-inspired model of neonatal conductive airways spanning the first few airway generations. We first perform at true scale in vitro particle image velocimetry measurements of respiratory flow patterns. Next, we explore in silico convective mass transport in computational fluid dynamics simulations by implementing Lagrangian tracking of tracer boli, where the ventilatory flow rate is fixed. Particle image velocimetry measurements at eight representative phase angles of a breathing cycle reveal similar flow patterns at peak velocity and during deceleration phases for conventional mechanical ventilation and high frequency oscillatory ventilation. Characteristic differences occur during the acceleration and flow reversal phases. Net displacements of the tracer particles rapidly reach asymptotic behaviour over cumulative breathing cycles and suggest a linear relation between tidal volume and convective mass transport. The linear relation observed suggests that differences in flow characteristics between conventional mechanical ventilation and high frequency oscillatory ventilation conditions do not substantially influence convective mass transport mechanisms. Lower tidal volumes thus cannot be compensated straight-forwardly by selecting higher frequencies to maintain similar ventilation efficiencies.
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