BACKGROUND Persistent hypercapnia after COPD exacerbation is associated with excess mortality and early rehospitalization. High Flow Nasal cannula (HFNC), may be theoretically an alternative to long-term noninvasive ventilation (NIV), since physiological studies have shown a reduction in PaCO2 level after few hours of treatment. In this clinical study we assessed the acceptability of HFNC and its effectiveness in reducing the level of PaCO2 in patients recovering from an Acute Hypercapnic Respiratory Failure (AHRF) episode. We also hypothesized that the response in CO2 clearance is dependent on baseline level of hypercapnia. METHODS Fifty COPD patients recovering from an acute exacerbation and with persistent hypercapnia, despite having attained a stable pH (i.e. pH > 7,35 and PaCO2 > 45 mmHg on 3 consecutive measurements), were enrolled and treated with HFNC for at least 8 h/day and during the nighttime RESULTS: HFNC was well tolerated with a global tolerance score of 4.0 ± 0.9. When patients were separated into groups with or without COPD/OSA overlap syndrome, the "pure" COPD patients showed a statistically significant response in terms of PaCO2 decrease (p = 0.044). In addition, the subset of patients with a lower pH at enrolment were those who responded best in terms of CO2 clearance (score test for trend of odds, p = 0.0038). CONCLUSIONS HFNC is able to significantly decrease the level of PaCO2 after 72 h only in "pure" COPD patients, recovering from AHRF. No effects in terms of CO2 reduction were found in those with overlap syndrome. The present findings will help guide selection of the best target population and allow a sample size calculation for future long-term randomized control trials of HFNC vs NIV. TRIAL REGISTRATION This study is registered with www. clinicaltrials.gov with identifier number NCT03759457.

中文翻译：

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高流量鼻插管对急性COPD急性加重后持续性高碳酸血症患者的影响：一项前瞻性研究。

背景技术COPD恶化后持续的高碳酸血症与死亡率过高和早期住院治疗有关。从理论上讲，高流量鼻插管（HFNC）可以替代长期无创通气（NIV），因为生理研究表明，经过数小时的治疗，PaCO2水平降低了。在这项临床研究中，我们评估了从急性高碳酸血症性呼吸衰竭（AHRF）发作中康复的患者中HFNC的可接受性及其在降低PaCO2水平方面的有效性。我们还假设二氧化碳清除的反应取决于高碳酸血症的基线水平。方法尽管已达到稳定的pH值（即连续3次测量pH值> 7,35且PaCO2> 45 mmHg），但仍有50名COPD患者从急性加重期恢复并伴有持续性高碳酸血症，结果：HFNC的耐受性良好，总体耐受评分为4.0±0.9。当将患者分为有或没有COPD / OSA重叠综合征的组时，“纯” COPD患者在PaCO2降低方面显示出统计学上显着的反应（p = 0.044）。此外，入组时pH较低的患者亚组是那些对CO2清除率反应最好的患者（赔率趋势评分测试，p = 0.0038）。结论HFNC仅在“纯” COPD患者中可在72 h后显着降低PaCO2的水平，并且可以从AHRF中恢复。在重叠综合征患者中，没有发现减少二氧化碳的影响。本研究结果将有助于指导最佳目标人群的选择，并为将来进行HFNC与NIV的长期随机对照试验进行样本量计算。试用注册本研究已在www.com.cn上注册。标识符为NCT03759457的Clinicaltrials.gov。