Department of Mechanical Engineering, University of Alberta, Edmonton, Alberta, Canada.
Medical R&D, Air Liquide Santé International, Centre de Recherche Paris-Saclay, Les Loges-en-Josas, France.
Respir Care. 2019 Feb;64(2):117-129. doi: 10.4187/respcare.06359. Epub 2019 Jan 29.
Portable oxygen concentrators (POCs) deliver oxygen in intermittent pulses. The challenge of establishing equivalence between continuous flow oxygen and nominal pulse flow settings on different POCs is well known. In vitro bench measurements and in silico mathematical modeling were used to compare the performance of 4 POCs versus continuous flow oxygen by predicting the F at the trachea and entering the acini.
Each of the 4 POCs was connected to a 3-dimensional printed replica of a human adult nasal airway via nasal cannula. A test lung simulated 3 breathing patterns representative of a patient with COPD at rest, during exercise, and while asleep. POCs were tested for each breathing pattern at all integer pulse flow settings. Volume-averaged F was calculated by analyzing oxygen concentrations and inhalation flow over time. In vitro oxygen waveforms were then combined with a single-path mathematical model of the lungs to assess oxygen transport through the conducting airways. In vitro experiments and mathematical modeling were repeated for continuous flow oxygen.
Continuous flow oxygen consistently delivered more (>2% absolute) oxygen in terms of volume-averaged F for all nominally equivalent pulse flow settings of >2. Differences were also observed when comparing performances between different POCs, particularly at high device settings (5 and 6). Simulations showed that efficiency of delivery to the acinar region of the lungs was higher in pulse flow than in continuous flow oxygen but that continuous flow oxygen generally delivered a higher absolute volume of oxygen. Differences in absolute oxygen delivery per breath between continuous flow oxygen and pulse flow were smaller for acinar delivery than for tracheal delivery.
Significant differences in POC performance based on volume-averaged F were found between pulse flow and continuous flow oxygen, and among pulse flow modes in different POCs. Although pulse flow was a more efficient mode of delivery than continuous flow oxygen, continuous flow oxygen delivered a greater absolute volume of oxygen per breath.
便携式氧气浓缩器（POC）以间歇性脉冲输送氧气。众所周知，在不同的 POC 上，要确定连续流量氧气与标称脉冲流量设置之间的等效性具有挑战性。本研究通过预测在气管和进入肺泡的 F 值，使用体外台架测量和计算机数学建模来比较 4 种 POC 与连续流量氧气的性能。
通过鼻插管将 4 种 POC 中的每一种与 3 维打印的成人鼻腔气道复制品相连。测试肺模拟了 3 种呼吸模式，代表休息、运动和睡眠时的 COPD 患者。对每种呼吸模式在所有整数脉冲流量设置下对 POC 进行测试。通过分析氧浓度和随时间变化的吸入流量来计算体积平均 F 值。然后，将体外氧波形与肺部的单路径数学模型相结合，以评估通过传导气道的氧输送。对连续流量氧气重复进行了体外实验和数学建模。
连续流量氧气在所有标称等效脉冲流量设置（>2）下，以体积平均 F 表示，始终输送更多（>2%绝对值）的氧气。当比较不同 POC 之间的性能时，也观察到差异，特别是在高设备设置（5 和 6）时。模拟表明，在脉冲流量下，向肺部肺泡区域输送的效率高于连续流量氧气，但连续流量氧气通常输送更高的绝对氧气量。与脉冲流量相比，连续流量氧气每呼吸一次的绝对氧气输送量差异较小，脉冲流量的肺泡输送比气管输送差异更小。
在体积平均 F 方面，基于脉冲流量和连续流量氧气以及不同 POC 中的脉冲流量模式，发现 POC 性能存在显著差异。尽管脉冲流量是比连续流量氧气更有效的输送模式，但连续流量氧气每呼吸一次输送的绝对氧气量更大。
