Ren Shuai, Shi Yan, Cai Maolin, Zhao Hongmei, Zhang Zhaozhi, Zhang Xiaohua Douglas
School of Automation Science and Electrical Engineering, Beihang University, Beijing, China.
The State Key Laboratory of Fluid Power Transmission and Control, Zhejiang University, Hangzhou, China.
Int J Numer Method Biomed Eng. 2018 Jun;34(6):e2978. doi: 10.1002/cnm.2978. Epub 2018 Mar 24.
Coughing is an irritable reaction that protects the respiratory system from infection and improves mucus clearance. However, for the patients who cannot cough autonomously, an assisted cough device is essential for mucus clearance. Considering the low efficiency of current assisted cough devices, a new simulated cough device based on the pneumatic system is proposed in this paper. Given the uncertainty of airflow rates necessary to clear mucus from airways, the computational fluid dynamics Eulerian wall film model and cough efficiency (CE) were used in this study to simulate the cough process and evaluate cough effectiveness. The Ansys-Matlab co-simulation model was set up and verified through experimental studies using Newtonian fluids. Next, model simulations were performed using non-Newtonian fluids, and peak cough flow (PCF) and PCF duration time were analyzed to determine their influence on mucus clearance. CE growth rate (λ) was calculated to reflect the CE variation trend. From the numerical simulation results, we find that CE rises as PCF increases while the growth rate trends to slow as PCF increases; when PCF changes from 60 to 360 L/min, CE changes from 3.2% to 51.5% which is approximately 16 times the initial value. Meanwhile, keeping a long PCF duration time could greatly improve CE under the same cough expired volume and PCF. The results indicated that increasing the PCF and PCF duration time can improve the efficiency of mucus clearance. This paper provides a new approach and a research direction for control strategy in simulated cough devices for airway mucus clearance.
咳嗽是一种保护性的应激反应，可保护呼吸系统免受感染并促进黏液清除。然而，对于无法自主咳嗽的患者，辅助咳嗽装置对于黏液清除至关重要。鉴于目前辅助咳嗽装置效率较低，本文提出了一种基于气动系统的新型模拟咳嗽装置。考虑到从气道清除黏液所需气流速率的不确定性，本研究采用计算流体动力学欧拉壁膜模型和咳嗽效率（CE）来模拟咳嗽过程并评估咳嗽效果。建立了Ansys-Matlab联合仿真模型，并通过使用牛顿流体的实验研究进行了验证。接下来，使用非牛顿流体进行模型仿真，分析峰值咳嗽流量（PCF）和PCF持续时间，以确定它们对黏液清除的影响。计算CE增长率（λ）以反映CE变化趋势。从数值模拟结果来看，我们发现随着PCF增加，CE升高，而增长率随着PCF增加趋于缓慢；当PCF从60 L/min变化到360 L/min时，CE从3.2%变化到51.5%，约为初始值的16倍。同时，在相同咳嗽呼出量和PCF条件下，保持较长的PCF持续时间可显著提高CE。结果表明，增加PCF和PCF持续时间可提高黏液清除效率。本文为气道黏液清除模拟咳嗽装置的控制策略提供了一种新方法和研究方向。
