Department of Neonatology, Yerevan State Medical University, Yerevan, Armenia.
Fisher & Paykel Healthcare, Auckland, New Zealand.
J Appl Physiol (1985). 2020 Apr 1;128(4):822-829. doi: 10.1152/japplphysiol.00871.2019. Epub 2020 Feb 20.
In newborns, it is unclear how nasal high flow (NHF) generates positive airway pressure. In addition, the reported benefits of NHF such as reduction in work of breathing may be independent of airway pressure. The authors hypothesized that during NHF the area of leak and the flow determine airway pressure and that NHF can reduce the required minute ventilation to maintain gas exchange. In response to NHF, pressure was measured in the upper airways of 9 newborns and ventilation was measured in another group of 17 newborns. In a bench model, airway pressures were measured during NHF with different prong sizes, nare sizes, and flows. The airway pressures during 8 L/min NHF were greater when a larger cannula versus a smaller cannula was used ( < 0.05). NHF reduced minute ventilation in 16 of 17 neonates, with a mean decrease of 24% from a baseline of 0.66 L/min (SD 0.21) ( < 0.001), and was unrelated to changes in airway pressure; arterial oxygen saturation by pulse oximetry () and tissue CO were unchanged. In the bench model, the airway pressure remained <2 cmHO when <50% of the "nare" was occluded by the prongs. As the leak area decreased, because of a smaller nare or a larger cannula, the airway pressure increased exponentially and was dependent on flow. In newborns NHF using room air substantially reduced minute ventilation without affecting gas exchange irrespective of a decrease or an increase of respiratory rate. NHF generates low positive airway pressure that exponentially increases with flow and occlusion of the nares. In healthy newborns, nasal high flow (NHF) with room air reduced minute ventilation by one-fourth without affecting gas exchange but, in contrast to adults, produced variable response in respiratory rate during sleep. During NHF, pressure in the upper airways did not exceed 2 cmHO at 8 L/min (3.4 L·min·kg) and was unaffected by opening of the mouth. NHF can generate higher pressure with larger prongs that decrease the leak around the cannula or by increasing the flow rate.
在新生儿中，鼻高流量（NHF）如何产生正压尚不清楚。此外，NHF 带来的益处，如减少呼吸功，可能与气道压力无关。作者假设，在 NHF 过程中，漏口面积和流量决定气道压力，并且 NHF 可以减少维持气体交换所需的分钟通气量。作者在 9 名新生儿中对上气道压力进行了测量，在另一组 17 名新生儿中进行了通气测量。在一个台式模型中，使用不同的鼻塞尺寸、鼻孔尺寸和流量来测量 NHF 时的气道压力。与使用较小的鼻塞相比，使用较大的鼻塞时 8 L/min NHF 的气道压力更高（<0.05）。NHF 降低了 17 名新生儿中的 16 名的分钟通气量，平均降低了 24%（从基线的 0.66 L/min[SD 0.21]）（<0.001），与气道压力变化无关；脉搏血氧饱和度（SpO2）和组织 CO 不变。在台式模型中，当鼻塞的<50%被鼻塞堵塞时，气道压力保持在<2 cmHO。随着漏口面积的减小，由于鼻孔较小或鼻塞较大，气道压力呈指数增加，并取决于流量。在新生儿中，使用空气的 NHF 显著降低了分钟通气量，而不影响气体交换，无论呼吸频率是降低还是增加。NHF 产生的低正压气道压随流量呈指数增加，并与鼻塞的堵塞程度有关。在健康的新生儿中，使用空气的 NHF 将分钟通气量降低了四分之一，而不影响气体交换，但与成人不同，在睡眠期间呼吸频率的反应不同。在 NHF 过程中，8 L/min（3.4 L·min·kg）时上气道压力不超过 2 cmHO，且不受张口的影响。NHF 可以使用更大的鼻塞来产生更高的压力，这些鼻塞可以减少围绕鼻塞的漏口，或者通过增加流速来产生更高的压力。
