Papamoschou D
Department of Mechanical and Aerospace Engineering University of California, Irvine 92717, USA.
Respir Physiol. 1995 Jan;99(1):183-90. doi: 10.1016/0034-5687(94)00071-7.
A theoretical analysis of convective gas transport validates the clinically demonstrated advantage of using helium-oxygen mixtures in treating patients with respiratory problems. Previous studies have attributed that advantage to the ability of helium-oxygen to stay laminar at higher velocities than nitrogen-oxygen. The present work shows that helium-oxygen does not need to be laminar to provide higher flow rates and that its benefits persist under turbulent conditions. The analysis is applied to steady flow through the lungs and through a circular airway obstruction. A simplified model of the lungs gives pressure-flow relations that show a significant increase in oxygen flow rate when nitrogen is substituted by helium. A similar improvement is found for flow through an obstruction. For a given pressure difference across the lungs or across an obstruction, the turbulent flow rate of oxygen increases by approximately 50% when nitrogen is replaced by helium in a mixture containing 20% oxygen.
对对流气体传输的理论分析证实了临床上所证明的使用氦氧混合气治疗呼吸问题患者的优势。先前的研究将该优势归因于氦氧混合气在比氮氧混合气更高的流速下仍能保持层流的能力。目前的研究表明，氦氧混合气无需保持层流就能提供更高的流速，并且在湍流条件下其益处依然存在。该分析应用于通过肺部和通过圆形气道阻塞的稳定气流。一个简化的肺部模型给出了压力-流量关系，结果显示当用氦气替代氮气时氧气流量显著增加。对于通过阻塞部位的气流也发现了类似的改善。对于跨肺部或跨阻塞部位的给定压力差，在含20%氧气的混合气中用氦气替代氮气时，氧气的湍流流速大约会增加50%。
