摘要目的:探讨使用非对称高流量鼻塞界面对慢性阻塞性肺疾病(COPD)模型呼气末二氧化碳(ETCO 2)和呼气末正压(PEEP)水平的影响。 方法:本研究为实验研究。将经鼻高流量氧疗(HFNC)设备、成人气道模型、模拟肺和CO 2气源相连接，在模型面部连接一个口鼻面罩以收集呼出的CO 2气体，并使用相应设备监测ETCO 2和PEEP水平。通过配套的模拟肺控制软件设置模拟肺的参数，模拟COPD患者的稳定期和加重期。比较在模拟的COPD稳定期和加重期状态下，使用不同鼻塞类别(对称鼻塞、单孔鼻塞和非对称鼻塞)、不同流速(0、10、20、30、40、50、60、70 L/min)和不同呼吸频率(25、30、35次/min)条件下，ETCO 2和PEEP水平的变化，并使用多元线性回归分析ETCO 2和PEEP的影响因素。 结果:当流速为40 L/min和50 L/min时，COPD稳定期模型中非对称鼻塞的ETCO 2水平最低，对称鼻塞的ETCO 2水平最高，单孔鼻塞居中(均 P<0.05)；当流速为10、20、40、50、60、70 L/min时，COPD加重期模型中非对称鼻塞的ETCO 2水平最低，对称鼻塞的ETCO 2水平最高，单孔鼻塞居中(均 P<0.05)；随着HFNC流速的增加，ETCO 2水平逐渐下降，在较低流速时，ETCO 2水平下降较为显著，而在较高流速时，ETCO 2水平下降趋于平缓。当流速为20、30、40、50、60、70 L/min时，COPD稳定期模型中对称鼻塞的PEEP水平最高，单孔鼻塞的PEEP水平最低，非对称鼻塞居中(均 P<0.01)；当流速为10、20、30、40、50、60、70 L/min时，COPD加重期模型中对称鼻塞的PEEP水平最高，单孔鼻塞的PEEP水平最低，非对称鼻塞居中(均 P<0.01)；随着HFNC流速的增加，PEEP水平逐渐升高。在COPD加重期模型中，使用非对称鼻塞，相同流速情况下，将呼吸频率分别调节至25、30、35次/min，结果显示ETCO 2和PEEP水平在呼吸频率35次/min时最高，呼吸频率25次/min时最低，呼吸频率30次/min时居中(均 P<0.05)。随着流速的增加，不同呼吸频率间的ETCO 2水平差距逐渐缩小，而PEEP水平差距逐渐增大。鼻塞种类、HFNC流速和COPD疾病状态是ETCO 2和PEEP的独立影响因素。 结论:与传统对称鼻塞和单孔鼻塞相比，HFNC连接非对称鼻塞界面能够更好地降低COPD模型的ETCO 2水平，并且在相对较低流速下就能实现很好的死腔清除效果；在形成PEEP方面，非对称鼻塞并不优于传统对称鼻塞，而优于单孔鼻塞。非对称鼻塞在不同呼吸频率下对CO 2清除和气道压力的影响存在复杂的流体力学关系。

abstractsObjective:This study aims to investigate the effects of asymmetrical high-flow nasal cannula interface on end-tidal carbon dioxide (ETCO 2) and positive end-expiratory pressure (PEEP) levels in chronic obstructive pulmonary disease (COPD) models. Methods:This was an in vitro experimental study.The high-flow nasal cannula oxygen therapy (HFNC) device, adult airway model, simulated lung, and a CO 2 source were connected.An oronasal mask was attached to the face of the model to collect exhaled CO 2, and an appropriate equipment was used to monitor the levels of ETCO 2 and PEEP.The parameters of the simulated lung were set using dedicated control software to simulate the stable and exacerbation phases of COPD.Changes in ETCO 2 and PEEP levels were compared under simulated stable and exacerbation conditions of COPD using various nasal cannula types (symmetric, single-lumen, and asymmetric), various flow rates (0 L/min, 10 L/min, 20 L/min, 30 L/min, 40 L/min, 50 L/min, 60 L/min, and 70 L/min), and respiratory rates (25 breaths/min, 30 breaths/min, and 35 breaths/min).Multivariate linear regression analysis was used to identify the factors influencing ETCO 2 and PEEP levels. Results:At flow rates of 40 L/min and 50 L/min, in the COPD stable-phase model, the highest ETCO 2 was obtained in the symmetric nasal cannula, followed by the single-lumen nasal cannula and asymmetric nasal cannula (all P<0.05).At flow rates of 10 L/min, 20 L/min, 40 L/min, 50 L/min, 60 L/min, and 70 L/min, in the COPD exacerbation-phase model, the highest ETCO 2 level was obtained in the symmetric nasal cannula, followed by the single-lumen nasal cannula and the asymmetric nasal cannula (all P<0.05).With increasing HFNC flow rates, ETCO 2 levels gradually decreased.The decline in ETCO 2 was more significant at lower flow rates, whereas at higher flow rates, the decrease plateaued.At flow rates of 20 L/min, 30 L/min, 40 L/min, 50 L/min, 60 L/min, and 70 L/min, in the COPD stable-phase model, the PEEP levels were the highest with the symmetric nasal cannula, followed by the asymmetric nasal cannula and the single-lumen nasal cannula (all P<0.01).At flow rates of 10 L/min, 20 L/min, 30 L/min, 40 L/min, 50 L/min, 60 L/min, and 70 L/min, in the COPD exacerbation-phase model, the PEEP levels were the highest with the symmetric nasal cannula, followed by the asymmetric nasal cannula and the single-lumen nasal cannula (all P<0.01).With increasing HFNC flow rates, PEEP levels gradually increased.In the COPD exacerbation-phase model, using the asymmetric nasal cannula at the same flow rates and adjusting the respiratory rates to 25 breaths/min, 30 breaths/min, and 35 breaths/min, the results showed that ETCO 2 and PEEP levels were the highest at 35 breaths/min, but lowest at 25 breaths/min, and intermediate at 30 breaths/min (all P<0.05).As the flow rate increased, the differences in ETCO 2 levels between different respiratory rates gradually diminished, whereas the differences in PEEP levels gradually increased.The type of nasal cannula, HFNC flow rate, and COPD disease state were identified as independent influencing factors for ETCO 2 and PEEP levels. Conclusions:Compared with traditional symmetric nasal cannulas and single-lumen nasal cannulas, the HFNC connected to an asymmetric nasal cannula interface achieves better reduction in ETCO 2 levels in COPD models and demonstrates an effective dead space clearance even at relatively low flow rates.The asymmetric nasal cannula is not superior to the traditional symmetric nasal cannula but outperforms the single-lumen nasal cannula in generating PEEP.The effects of the asymmetric nasal cannula on CO 2 clearance and airway pressure at different respiratory rates exhibit a complex fluid dynamic relationship.