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Title:: Residue state numerical simulation of the CO2 in whole-face sleep respirator mask and its optimal design

作者:: 李振潇1; 2; 张翼飞1; 3; 张治国1△; 1.常州大学生物医学工程与健康科学研究院，江苏常州 213164；2.常州大学机械工程学院，江苏常州 213164；3. 常州大学信息数理学院，江苏常州 213164

Author(s):: LI Zhenxiao1; 2; ZHANG Yifei1; 3; ZHANG Zhiguo1; 1. Institute of Biomedical Engineering and Health Sciences, Changzhou University, Changzhou 216164, China; 2. School of Mechanical Engineering, Changzhou University, Changzhou 213164; 3. School of Mathematics & Physics, Changzhou University, Changzhou 213164

Keywords:: Obstructive sleep apnea hypopnea syndrome; Continuous positive airway pressure; Respiratory mask; Computational fluid dynamics; Residual concentration of the CO2

摘要:: 阻塞性睡眠呼吸暂停低通气综合症（OSAHS）以呼吸受限和反复暂停为主要症状，目前最佳的治疗方式是通过家用睡眠呼吸机对用户上气道施加持续的正压通气（CPAP）。但呼吸机面罩若设计不当，可能导致局部“高浓度”CO2的反复吸入，长期对用户的健康不利。本研究以全脸式呼吸机面罩为研究对象，通过计算流体动力学（CFD）的方法分析面罩内CO2的残留状况及流场特征变化，并以此为依据开展优化设计。结果表明呼气末时刻鼻孔附近CO2的残留浓度约为3%，且会被反复吸入，长期将影响用户健康；若将排气孔设计在面罩前端，鼻孔附近CO2的残留浓度将降低到2%，即CO2的反复吸入量减少33.3%。本研究为家用睡眠呼吸机面罩基于空气动力学的个体化优化设计提供了重要的理论指导。

Abstract:: Obstructive sleep apnea-hypopnea syndrome (OSAHS), is characterized by breathing restriction and repeated pause during sleeping. At present, the best treatment is to apply continuous positive airway pressure (CPAP) on the patient’s upper airway through a household sleep ventilator. However, improper design of the respiratory mask may lead to repeated inhalation of the local “high concentration” CO2, which will have adverse effect on the health of users in long term use. We numerically simulated the residual state of the CO2 by using the method of computational fluid dynamics (CFD) based on a whole-face respirator. Furtherly, a series of structure optimal design were performed in accordance with the simulation results. Results showed that at the end of expiratory time, the residual concentration of the CO2 near the nostrils was about 3%, which would be inhaled again and was harmful to users’ health. Meanwhile, if the exhaust holes positioned in the front of the mask, the residual concentration of the CO2 near the nostrils would be reduced to 2%, 33.3% decrease of the repeated inhalation. This study provides important theoretical guidelines for the individualized optimal design of the respiratory masks utilized in the household sleep ventilators based on aerodynamics.