Zhou Steven, Chatburn Robert L
Respir Care. 2014 Aug;59(8):1199-209. doi: 10.4187/respcare.02878.
The F(IO(2)) for a nasal cannula with constant flow (CF) depends on the anatomic reservoir (AR), which is affected by changes in frequency and end-expiratory flow. Conversely, pulse flow (PF) devices do not require the AR. The purpose of this study was to compare the F(IO(2)) delivered by a nasal cannula supplied by CF via oxygen tank with that delivered by PF delivered via portable oxygen concentrator. Hypotheses were (1) a lung model of COPD with non-zero end-expiratory flow decreases F(IO(2)) for CF more than for PF, and (2) CF and PF perform differently in terms of F(IO(2)) delivery, despite having equivalent settings.
Normal and COPD lung models were simulated (IngMar Medical ASL 5000) using published human data: normal: breathing frequency = 15 breaths/min, R(in) = 4 cm H2O · s · L(-1), R(out) = 4 cm H2O · s · L(-1), C = 60 mL · cm H2O(-1), tidal volume (VT) = 685 mL, P(max) = 11.95 cm H2O, increase = 33%, and release = 28; COPD: breathing frequency = 20 breaths/min, R(in) = 12 cm H2O · s · L(-1), R(out) = 25 cm H2O · s · L(-1), C = 66 mL · cm H2O(-1), VT = 685 mL, Pmax = 24.52 cm H2O, increase = 35%, and release = 23%. CF was 1-5 L/min. Portable oxygen concentrators used were Solo2 (Invacare), XPO2 (Invacare), FreeStyle (AirSep), Focus (AirSep), One G3 (Inogen), and LifeChoice ActivOx (Inova Labs).
CF produced significantly higher F(IO(2)) at all settings for normal lungs but lower for COPD lungs compared with Solo2. COPD reduced the F(IO(2)) for CF but had a smaller variable effect for PF. Data show there is no equivalency between PF setting and CF rates for the portable oxygen concentrators tested.
CF oxygen delivery via a nasal cannula is significantly reduced by elimination of the AR in a model of COPD, yielding clinically important decreases in F(IO(2)). PF (delivered with a portable oxygen concentrator) is relatively unaffected. This study supports the recommendation that clinicians and caretakers should titrate the PF setting to each patient's unique oxygen requirements.
恒流（CF）鼻导管的吸入氧分数（F(IO(2))）取决于解剖学贮气室（AR），而AR会受到频率和呼气末流量变化的影响。相反，脉冲流（PF）装置不需要AR。本研究的目的是比较通过氧气罐提供CF的鼻导管所输送的F(IO(2))与通过便携式制氧机输送PF所提供的F(IO(2))。假设为：（1）呼气末流量非零的慢性阻塞性肺疾病（COPD）肺模型使CF的F(IO(2))降低幅度大于PF；（2）尽管CF和PF设置相同，但在F(IO(2))输送方面表现不同。
使用已发表的人体数据模拟正常和COPD肺模型（IngMar Medical ASL 5000）：正常：呼吸频率 = 15次/分钟，吸气阻力（R(in)） = 4厘米水柱·秒·升⁻¹，呼气阻力（R(out)） = 4厘米水柱·秒·升⁻¹，顺应性（C） = 60毫升·厘米水柱⁻¹，潮气量（VT） = 685毫升，最大压力（P(max)） = 11.95厘米水柱，增加 = 33%，释放 = 28；COPD：呼吸频率 = 20次/分钟，R(in) = 12厘米水柱·秒·升⁻¹，R(out) = 25厘米水柱·秒·升⁻¹，C = 66毫升·厘米水柱⁻¹，VT = 685毫升，Pmax = 24.52厘米水柱，增加 = 35%，释放 = 23%。CF为1 - 5升/分钟。使用的便携式制氧机有Solo2（英维康）、XPO2（英维康）、FreeStyle（AirSep）、Focus（AirSep）、One G3（因诺金）和LifeChoice ActivOx（Inova Labs）。
与Solo2相比，在所有设置下，CF在正常肺时产生的F(IO(2))显著更高，但在COPD肺时更低。COPD降低了CF的F(IO(2))，但对PF的影响变量较小。数据表明，对于所测试的便携式制氧机，PF设置与CF流速之间不存在等效性。
在COPD模型中，通过消除AR，经鼻导管进行CF氧输送时F(IO(2))显著降低，导致临床上F(IO(2))出现重要下降。PF（通过便携式制氧机输送）相对不受影响。本研究支持临床医生和护理人员应根据每位患者独特的氧气需求调整PF设置的建议。
