Ms Sabz, Drs Finlay, Rouhani, and Martin are affiliated with the Department of Mechanical Engineering, University of Alberta, Edmonton, Alberta, Canada. Dr Noga is affiliated with the Department of Radiology and Diagnostic Imaging, University of Alberta, Edmonton, Alberta, Canada.
Respir Care. 2024 Mar 27;69(4):438-448. doi: 10.4187/respcare.11438.
The nasal cannula is widely regarded as a safe and effective means of administering low- and high-flow oxygen to patients irrespective of their age. However, variability in delivered oxygen concentration (F F ) via nasal cannula has the potential to pose health risks. The present study aimed to evaluate predictive equations for F over a large parameter space, including variation in breathing, oxygen flow, and upper-airway geometry representative of both young children and adults.
Realistic nasal airway geometries were previously collected from medical scans of adults, infants, and neonates. Nasal airway replicas based on these geometries were used to measure the F for low-flow oxygen delivery during simulated spontaneous breathing. The present study extends previously published data sets to include higher oxygen flows. The extended data sets included nasal cannula oxygen flows that ranged from 6 to 65 L/min for the adult replicas, and from 0.5 to 6 L/min for the infant replicas. For both age groups, F was measured over a range of breathing frequencies, inspiratory to expiratory time ratios, and tidal volumes. Measured F values were compared with values predicted by using a previously derived flow-weighted equation.
For both age groups, F was observed to increase nonlinearly with the ratio between oxygen flow supplied to the nasal cannula and the average inhalation flow. The previously derived flow-weighted equation over-predicted F at higher oxygen flows. A new empirical equation, therefore, was proposed to predict F for either age group as a function of nasal cannula flow, tidal volume, and inspiratory time. Predicted F values matched measured values, with average relative errors of 2.4% for infants and 4.3% for adults.
A new predictive equation for F was obtained that accurately matched measured data in both adult and infant airway replicas for low- and high-flow regimens.
鼻导管被广泛认为是一种安全有效的低流量和高流量给氧方式，适用于各种年龄段的患者。然而，鼻导管输送的氧气浓度（F F ）存在变化，这可能会对健康造成风险。本研究旨在评估在较大参数空间内预测 F 的预测方程，包括呼吸、氧气流量和代表婴幼儿和成年人的上呼吸道几何形状的变化。
先前从成人、婴儿和新生儿的医学扫描中收集了真实的鼻气道几何形状。基于这些几何形状的鼻气道复制品用于测量模拟自主呼吸时低流量氧气输送的 F F 。本研究扩展了以前发表的数据组，包括更高的氧气流量。扩展的数据组包括成人复制品的鼻导管氧气流量范围为 6 至 65 L/min，婴儿复制品的氧气流量范围为 0.5 至 6 L/min。对于两个年龄组，在一系列呼吸频率、吸气到呼气时间比和潮气量范围内测量了 F F 。将测量的 F F 值与使用先前推导的流量加权方程预测的值进行了比较。
对于两个年龄组，F F 均观察到与鼻导管供应的氧气流量与平均吸入流量之比呈非线性增加。先前推导的流量加权方程在较高氧气流量下高估了 F F 。因此，提出了一个新的经验公式，以预测两个年龄组的 F F 作为鼻导管流量、潮气量和吸气时间的函数。预测的 F F 值与测量值匹配，婴儿的平均相对误差为 2.4%，成人的平均相对误差为 4.3%。
获得了一个新的 F F 预测方程，该方程在成人和婴儿气道复制品的低流量和高流量方案中准确匹配了测量数据。
