Background

High-flow oxygen therapy via nasal cannula (HFOT_NASAL) increases airway pressure, ameliorates oxygenation and reduces work of breathing. High-flow oxygen can be delivered through tracheostomy (HFOT_TRACHEAL), but its physiological effects have not been systematically described. We conducted a cross-over study to elucidate the effects of increasing flow rates of HFOT_TRACHEAL on gas exchange, respiratory rate and endotracheal pressure and to compare lower airway pressure produced by HFOT_NASAL and HFOT_TRACHEAL.

Methods

Twenty-six tracheostomized patients underwent standard oxygen therapy through a conventional heat and moisture exchanger, and then HFOT_TRACHEAL through a heated humidifier, with gas flow set at 10, 30 and 50 L/min. Each step lasted 30 min; gas flow sequence during HFOT_TRACHEAL was randomized. In five patients, measurements were repeated during HFOT_TRACHEAL before tracheostomy decannulation and immediately after during HFOT_NASAL. In each step, arterial blood gases, respiratory rate, and tracheal pressure were measured.

Results

During HFOT_TRACHEAL, PaO₂/FiO₂ ratio and tracheal expiratory pressure slightly increased proportionally to gas flow. The mean [95% confidence interval] expiratory pressure raise induced by 10-L/min increase in flow was 0.2 [0.1–0.2] cmH₂O (ρ = 0.77, p < 0.001). Compared to standard oxygen, HFOT_TRACHEAL limited the negative inspiratory swing in tracheal pressure; at 50 L/min, but not with other settings, HFOT_TRACHEAL increased mean tracheal expiratory pressure by (mean difference [95% CI]) 0.4 [0.3–0.6] cmH₂O, peak tracheal expiratory pressure by 0.4 [0.2–0.6] cmH₂O, improved PaO₂/FiO₂ ratio by 40 [8–71] mmHg, and reduced respiratory rate by 1.9 [0.3–3.6] breaths/min without PaCO₂ changes. As compared to HFOT_TRACHEAL, HFOT_NASAL produced higher tracheal mean and peak expiratory pressure (at 50 L/min, mean difference [95% CI]: 3 [1–5] cmH₂O and 4 [1–7] cmH₂O, respectively).

Conclusions

As compared to standard oxygen, 50 L/min of HFOT_TRACHEAL are needed to improve oxygenation, reduce respiratory rate and provide small degree of positive airway expiratory pressure, which, however, is significantly lower than the one produced by HFOT_NASAL.

中文翻译：

---

高流量氧气对气管切开术患者的生理影响

背景

通过鼻插管（HFOT _NASAL）进行的高流量氧气疗法会增加气道压力，改善氧合作用并减少呼吸功。高流量氧气可以通过气管切开术（HFOT _TRACHEAL）输送，但尚未对其生理作用进行系统描述。我们进行了一项交叉研究，以阐明增加HFOT TRACHEAL_流速对气体交换，呼吸频率和气管内压力的影响，并比较HFOT _NASAL和HFOT _TRACHEAL产生的较低气道压力_。

方法

26例气管切开术的患者通过常规的热湿交换器进行了标准的氧气治疗，然后通过加热的加湿器进行了HFOT _TRACHEAL，气体流量设置为_10、30和50 L / min。每个步骤持续30分钟；HFOT_气管插管期间的气流顺序是随机的。在5例患者中，在气管切开术脱_管前和在HFOT _NASAL期间立即进行HFOT _TRACHEAL期间重复_测量。在每个步骤中，都要测量动脉血气，呼吸频率和气管压力。

结果

在HFOT气管插管期间，PaO ₂ / _{FiO 2}比和气管呼气压力与气流成比例地增加。流量增加10 L / min引起的平均呼气压力[95％置信区间]为0.2 [0.1-0.2] cmH ₂ O（ρ  = 0.77，p  <0.001）。与标准氧气相比，HFOT _TRACHEAL限制了气管压力的负吸气摆动；在50升/分钟，但不与其他设置，HFOT_气管由（平均差异[95％CI]）增加的平均气管呼气压力0.4 [0.3-0.6] CMH ₂ O，峰气管呼气压力0.4 [0.2-0.6] cmH ₂ O，改善的PaO₂ / FiO ₂比率降低40 [8-71] mmHg，呼吸速率每分钟降低1.9 [0.3-3.6]呼吸/分钟，而PaCO ₂不变。相比于HFOT_气管，HFOT _NASAL产生更高气管平均和峰值呼气压力（在50升/分钟，平均差异[95％CI]：3 [1-5] CMH ₂ O和4 [1-7] CMH ₂ ö ， 分别）。

结论

与标准氧气相比，需要50 L / min的HFOT _TRACHEAL改善氧合作用，降低呼吸频率并提供较小的正气道呼气压力，但是，这明显低于HFOT _NASAL产生的正气道_压力。