Department of Anaesthesiology and Critical Care Medicine, University of Cologne, Faculty of Medicine and University Hospital of Cologne, Kerpener Str. 62, 50937, Cologne, Germany.
Department of Anesthesiology and Intensive Care, German armed forces Central Hospital of Koblenz, Koblenz, Germany.
BMC Anesthesiol. 2021 Oct 7;21(1):239. doi: 10.1186/s12871-021-01461-z.
Preoxygenation and application of apneic oxygenation are standard to prevent patients from desaturation e.g. during emergency intubation. The time before desaturation occurs can be prolonged by applying high flow oxygen into the airway. Aim of this study was to scientifically assess the flow that is necessary to avoid nitrogen entering the airway of a manikin model during application of pure oxygen via high flow nasal oxygen.
We measured oxygen content over a 20-min observation period for each method in a preoxygenated test lung applied to a human manikin, allowing either room air entering the airway in control group, or applying pure oxygen via high flow nasal oxygen at flows of 10, 20, 40, 60 and 80 L/min via nasal cannula in the other groups. Our formal hypothesis was that there would be no difference in oxygen fraction decrease between the groups.
Oxygen content in the test lung dropped from 97 ± 1% at baseline in all groups to 43 ± 1% in the control group (p < 0.001 compared to all other groups), to 92 ± 1% in the 10 L/min group, 92 ± 1% in the 20 L/min group, 90 ± 1% in the 40 L/min group, 89 ± 0% in the 60 L/min group and 87 ± 0% in the 80 L/min group. Apart from comparisons 10 l/ min vs. 20 L/min group (p = .715) and 10/L/min vs. 40 L/min group (p = .018), p was < 0.009 for all other comparisons.
Simulating apneic oxygenation in a preoxygenated manikin connected to a test lung over 20 min by applying high flow nasal oxygen resulted in the highest oxygen content at a flow of 10 L/min; higher flows resulted in slightly decreased oxygen percentages in the test lung.
预充氧和应用无通气氧合是预防患者在紧急插管时发生低氧血症的标准措施。通过向气道输送高流量氧气，可以延长发生低氧血症的时间。本研究的目的是科学评估在通过高流量鼻氧给预充氧的模型应用纯氧时，避免氮气进入气道所需的流量。
我们在一个预充氧的测试肺模型中测量了 20 分钟观察期内每种方法的氧含量，其中一组为对照组，允许空气进入气道；其他组通过鼻导管在高流量鼻氧下以 10、20、40、60 和 80 L/min 的流速输送纯氧。我们的正式假设是，各组之间的氧分数下降不会有差异。
所有组的测试肺中的氧含量从基线时的 97±1%降至对照组的 43±1%（与所有其他组相比，p<0.001），10 L/min 组为 92±1%，20 L/min 组为 92±1%，40 L/min 组为 90±1%，60 L/min 组为 89±0%，80 L/min 组为 87±0%。除了 10 L/min 与 20 L/min 组之间的比较（p=0.715）和 10 L/min 与 40 L/min 组之间的比较（p=0.018）外，其他所有比较的 p 值均<0.009。
在连接到测试肺的预充氧人体模型中，通过高流量鼻氧应用模拟无通气氧合 20 分钟后，在流速为 10 L/min 时获得了最高的氧含量；较高的流速导致测试肺中的氧百分比略有下降。
