Chikata Yusuke, Ohnishi Saki, Nishimura Masaji
Medical Equipment Center, Tokushima University Hospital, 2-50-1 Kuramoto, Tokushima 770-8503, Japan.
Faculty of Medicine, Tokushima University, 3-18-15 Kuramoto, Tokushima 770-8503, Japan.
Respir Care. 2017 May;62(5):532-537. doi: 10.4187/respcare.05319. Epub 2017 Feb 7.
High-flow nasal cannula therapy (HFNC) for neonate/infants can deliver up to 10 L/min of heated and humidified gas, and F can be adjusted to between 0.21 and 1.0. With adults, humidification and actual F are known to vary according to inspiratory and HFNC gas flow, tidal volume (V), and ambient temperature. There have been few studies focused on humidification and F in HFNC settings for neonates/infants, so we performed a bench study to investigate the influence of gas flow, ambient temperature, and respiratory parameters on humidification and actual F in a neonate/infant simulation.
HFNC gas flow was set at 3, 5, and 7 L/min, and F was set at 0.3, 0.5, and 0.7. Spontaneous breathing was simulated using a 2-bellows-in-a-box model of a neonate lung. Tests were conducted with V settings of 20, 30, and 40 mL and breathing frequencies of 20 and 30 breaths/min. Inspiratory time was 0.8 s with decelerating flow waveform. The HFNC tube was placed in an incubator, which was either set at 37°C or turned off. Absolute humidity (AH) and actual F were measured for 1 min using a hygrometer and an oxygen analyzer, and data for the final 3 breaths were extracted.
At all settings, when the incubator was turned on, AH was greater than when it was turned off ( < .001). When the incubator was turned off, as gas flow increased, AH increased ( < .001); however, V did not affect AH ( = .16). As gas flow increased, actual F more closely corresponded to set F . When gas flow was 3 L/min, measured F decreased proportionally more at each F setting increment ( < .001).
AH was affected by ambient temperature and HFNC gas flow. Actual F depended on V when gas flow was 3 L/min.
新生儿/婴儿的高流量鼻导管治疗（HFNC）可输送高达10L/min的加热加湿气体，氧浓度（F）可在0.21至1.0之间调节。对于成人，已知加湿情况和实际氧浓度会根据吸气和HFNC气体流量、潮气量（V）以及环境温度而变化。针对新生儿/婴儿HFNC环境下的加湿和氧浓度的研究较少，因此我们进行了一项实验台研究，以探讨气体流量、环境温度和呼吸参数对新生儿/婴儿模拟环境中加湿和实际氧浓度的影响。
将HFNC气体流量设置为3、5和7L/min，氧浓度设置为0.3、0.5和0.7。使用新生儿肺的双波纹管箱模型模拟自主呼吸。在潮气量设置为20、30和40mL以及呼吸频率为20和30次/分钟的情况下进行测试。吸气时间为0.8秒，流量波形呈减速状态。将HFNC管放置在设置为37°C或关闭的培养箱中。使用湿度计和氧分析仪测量1分钟的绝对湿度（AH）和实际氧浓度，并提取最后3次呼吸的数据。
在所有设置下，当培养箱开启时，绝对湿度大于关闭时（P<0.001）。当培养箱关闭时，随着气体流量增加，绝对湿度增加（P<0.001）；然而，潮气量对绝对湿度没有影响（P = 0.16）。随着气体流量增加，实际氧浓度更接近设定的氧浓度。当气体流量为3L/min时，在每个氧浓度设置增量下，测量的氧浓度下降比例更大（P<0.001）。
绝对湿度受环境温度和HFNC气体流量影响。当气体流量为3L/min时，实际氧浓度取决于潮气量。
