Huang Chao-Lan, Lu Chun-Ching, Chiang Cheng, Chao Heng-Sheng, Chiang Ting-Yun, Teng Wei-Nung, Chang Wen-Kuei, Ting Chien-Kun
Department of Anesthesiology, Taipei Veterans General Hospital, Taipei, Taiwan; Department of Anesthesiology, School of Medicine, National Yang Ming Chiao Tung University, Taipei, Taiwan.
Department of Orthopedics and Traumatology, National Yang Ming Chiao Tung University Hospital, Yilan, Taiwan; Department of Orthopedics, School of Medicine, National Yang Ming Chiao Tung University, Taipei, Taiwan.
J Formos Med Assoc. 2025 Aug;124(8):718-723. doi: 10.1016/j.jfma.2024.08.006. Epub 2024 Aug 12.
Purpose: High-flow nasal cannula (HFNC) has many benefits in various clinical conditions. The original hypothesis suggests that the high and constant fraction of inspired oxygen (FiO) is one of the main physiological effects. However, increasing evidence shows that there is a gap between the actual FiO and administered FiO. We aimed to determine the actual FiO under different respiratory conditions and develop a regression model using a spontaneous breathing lung model.
A spontaneous breathing simulation model was built using an airway manikin and a model lung. The FiO was measured under different respiratory conditions with varying tidal volumes and respiratory and HFNC flow rates. The relationships between the respiratory parameters and actual FiO were determined and used to build the predictive model.
The actual FiO was negatively correlated with respiratory rate and tidal volume and positively correlated with HFNC flow. The regression model could not be developed using simple respiratory parameters. Therefore, we introduced a new variable, defined as flow ratio, which equaled the HFNC flow divided by inspiratory flow. Our equation demonstrated that the actual FiO was mainly determined by the flow ratio in a non-linear relationship. Accordingly, a flow ratio greater than 1 did not ensure a constant high FiO, whereas a flow ratio >1.435 could produce FiO >0.9.
The FiO during HFNC was not constant even at sufficiently high oxygen flow compared with inspiratory flow. The predictive model showed that the actual FiO was mainly determined by the flow ratio.
目的：高流量鼻导管（HFNC）在各种临床情况下有诸多益处。最初的假设表明，高且恒定的吸入氧分数（FiO）是主要的生理效应之一。然而，越来越多的证据表明，实际FiO与给予的FiO之间存在差距。我们旨在确定不同呼吸条件下的实际FiO，并使用自主呼吸肺模型建立回归模型。
使用气道人体模型和模型肺构建自主呼吸模拟模型。在不同呼吸条件下，改变潮气量、呼吸频率和HFNC流速，测量FiO。确定呼吸参数与实际FiO之间的关系，并用于建立预测模型。
实际FiO与呼吸频率和潮气量呈负相关，与HFNC流速呈正相关。无法使用简单的呼吸参数建立回归模型。因此，我们引入了一个新变量，定义为流量比，即HFNC流速除以吸气流量。我们的方程表明，实际FiO主要由流量比以非线性关系决定。因此，流量比大于1并不能确保恒定的高FiO，而流量比>1.435可产生FiO>0.9。
即使与吸气流量相比氧流量足够高，HFNC期间的FiO也不恒定。预测模型表明，实际FiO主要由流量比决定。
