Adams Cletus F, Geoghegan Patrick H, Spence Callum J, Jermy Mark C
Department of Mechanical Engineering, University of Canterbury, Christchurch 8041, New Zealand.
School of Life and Health Sciences, Aston University, Birmingham, B4 7ET, England, United Kingdom.
Respir Physiol Neurobiol. 2018 Aug;254:23-29. doi: 10.1016/j.resp.2018.03.014. Epub 2018 Apr 7.
The goal of this paper is to quantify upper airway resistance with and without nasal high flow (NHF) therapy. For adults, NHF therapy feeds 30-60 L/min of warm humidified air into the nose through short cannulas which do not seal the nostril. NHF therapy has been reported to increase airway pressure, increase tidal volume (V) and decrease respiratory rate (RR), but it is unclear how these findings affect the work done to overcome airway resistance to air flow during expiration. Also, there is little information on how the choice of nasal cannula size may affect work of breathing. In this paper, estimates of airway resistance without and with different NHF flow (applied via different cannula sizes) were made. The breathing efforts required to overcome airway resistance under these conditions were quantified.
NHF was applied via three different cannula sizes to a 3-D printed human upper airway. Pressure drop and flow rate were measured and used to estimate inspiratory and expiratory upper airway resistances. The resistance information was used to compute the muscular work required to overcome the resistance of the upper airway to flow.
NHF raises expiratory resistance relative to spontaneous breathing if the breathing pattern does not change but reduces work of breathing if peak expiratory flow falls. Of the cannula sizes used, the large cannula produced the greatest resistance and the small cannula produced the least. The work required to cause tracheal flow through the upper airway was reduced if the RR and minute volume are reduced by NHF. NHF has been observed to do so in COPD patients (Bräunlich et al., 2013). A reduction in I:E ratio due to therapy was found to reduce work of breathing if the peak inspiratory flow is less than the flow below which no inspiratory effort is required to overcome upper airway resistance.
NHF raises expiratory resistance but it can reduce the work required to overcome upper airway resistance via a fall in inspiratory work of breathing, RR and minute volume.
本文的目的是量化在使用和不使用经鼻高流量（NHF）治疗时的上气道阻力。对于成年人，NHF治疗通过不封闭鼻孔的短插管将30 - 60升/分钟的温热湿润空气送入鼻腔。据报道，NHF治疗可增加气道压力、增加潮气量（V）并降低呼吸频率（RR），但尚不清楚这些结果如何影响呼气过程中克服气流气道阻力所做的功。此外，关于鼻插管尺寸的选择如何影响呼吸功的信息很少。在本文中，对不使用NHF和使用不同NHF流量（通过不同尺寸插管应用）时的气道阻力进行了估计。对在这些条件下克服气道阻力所需的呼吸努力进行了量化。
通过三种不同尺寸的插管将NHF应用于3D打印的人体上气道。测量压力降和流速，并用于估计吸气和呼气上气道阻力。阻力信息用于计算克服上气道气流阻力所需的肌肉功。
如果呼吸模式不变，NHF相对于自主呼吸会增加呼气阻力，但如果呼气峰值流量下降，则会降低呼吸功。在所使用的插管尺寸中，大尺寸插管产生的阻力最大，小尺寸插管产生的阻力最小。如果NHF降低RR和分钟通气量，则通过上气道产生气管气流所需的功会减少。在慢性阻塞性肺疾病（COPD）患者中已观察到NHF有此作用（布劳尼希等人，2013年）。如果吸气峰值流量小于无需吸气努力即可克服上气道阻力的流量，则发现治疗导致的吸气与呼气时间比（I:E比）降低会减少呼吸功。
NHF会增加呼气阻力，但它可通过降低吸气呼吸功、RR和分钟通气量来减少克服上气道阻力所需的功。
