Analysis of the Efficiency of Treating 20 Critical Cases of 2019-nCoV with High-Flow Nasal Cannula Oxygen Therapy in Chongqing

Mei YANG; An ZHANG; Yu-yan SONG; Yao-kai CHEN

doi:10.13718/j.cnki.xdzk.2020.03.004

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Objective:To evaluate the efficacy of the high-flow nasal cannula oxygen therapy (HFNC) for treatment of severe new coronavirus pneumonia (NCP) patients. Methods:The clinical data of 20 cases of severe NCP patients receiving HFNC treatment in Chongqing Public Medical Treatment Center from January 24, 2020 to February 23, 2020 were retrospectively analyzed. Results:After treatment, the symptoms and oxygenation index (P/F) of 7 patients (35% of the total) improved, and HFNC treatment continued. The other 13 patients (65%) showed no improvement or became worse, and they were treated with noninvasive ventilation (NIV) or invasive mechanical ventilation (IMV) in stead. There was no significant difference in gender, age, basic diseases and other general information between the two groups of patients (p>0.05), but the average age of the patients of the HFNC failure group (57.76 years) was higher than that of the success group (63.3 years). Results Single-factor analysis of failure risk showed no statistically significant differences (p>0.05) between the two groups in their respiratory rate, CD4+cell count, oxygenation index, initial ROX (rate-oxygenation) index and 12 hours ROX, but the patients who succeeded in treatment had higher baseline SaO₂, 2 hours after treatment ROX index and 12 hours ROX index after treatment (p < 0.05). The Cox risk ratio model was used to analyze factors with p < 0.05 in single factor molecules and baseline P/F, and it was found that baseline SaO₂, baseline P/F and ROX index at 2 h and 12 h after treatment were not independent risk factors for HFNC treatment failure, but the lower their values, the greater the risk of failure with HFNC. With a baseline P/F lower than 200 mmHg, the risk of failure was higher than that of P/F ≥ 200 mmHg. Conclusion:HFNC can be used to treat severe NCP patients with P/F ≥ 200 mmHg, while in patients with baseline P/F < 200 mmHg or age ≥ 50 y, the risk of treatment failure is higher.

Corresponding author: Yao-kai CHEN

Received Date: 03/03/2020

Available Online: 20/03/2020

Key words:

high-flow nasal cannula oxygen therapy /
novel coronavirus pneumonia /
efficacy analysis /
mechanical ventilation /
ROX index

Abstract: Objective:To evaluate the efficacy of the high-flow nasal cannula oxygen therapy (HFNC) for treatment of severe new coronavirus pneumonia (NCP) patients. Methods:The clinical data of 20 cases of severe NCP patients receiving HFNC treatment in Chongqing Public Medical Treatment Center from January 24, 2020 to February 23, 2020 were retrospectively analyzed. Results:After treatment, the symptoms and oxygenation index (P/F) of 7 patients (35% of the total) improved, and HFNC treatment continued. The other 13 patients (65%) showed no improvement or became worse, and they were treated with noninvasive ventilation (NIV) or invasive mechanical ventilation (IMV) in stead. There was no significant difference in gender, age, basic diseases and other general information between the two groups of patients (p>0.05), but the average age of the patients of the HFNC failure group (57.76 years) was higher than that of the success group (63.3 years). Results Single-factor analysis of failure risk showed no statistically significant differences (p>0.05) between the two groups in their respiratory rate, CD4+cell count, oxygenation index, initial ROX (rate-oxygenation) index and 12 hours ROX, but the patients who succeeded in treatment had higher baseline SaO₂, 2 hours after treatment ROX index and 12 hours ROX index after treatment (p < 0.05). The Cox risk ratio model was used to analyze factors with p < 0.05 in single factor molecules and baseline P/F, and it was found that baseline SaO₂, baseline P/F and ROX index at 2 h and 12 h after treatment were not independent risk factors for HFNC treatment failure, but the lower their values, the greater the risk of failure with HFNC. With a baseline P/F lower than 200 mmHg, the risk of failure was higher than that of P/F ≥ 200 mmHg. Conclusion:HFNC can be used to treat severe NCP patients with P/F ≥ 200 mmHg, while in patients with baseline P/F < 200 mmHg or age ≥ 50 y, the risk of treatment failure is higher.

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近期研究发现，对于新发生的呼吸衰竭，经鼻高流量氧疗(high-flow nasal cannula oxygen therapy，HFNC)在病死率方面优于无创通气(noninvasive ventilation，NIV)和标准氧疗(standard oxygen)^[1].文献[2]也指出，当重型、危重型患者接受标准氧疗后呼吸窘迫和(或)低氧血症无法缓解时，可考虑使用高流量鼻导管氧疗或无创通气.但重型新型冠状病毒肺炎(novel coronavirus pneumonia，NCP)患者多存在免疫功能受损，而在免疫功能低下的患者中，HFNC相对于标准氧疗的优势尚未得到证实^[3-5]. ROX指数(rate-oxygenation index)可以很好地预测HFNC的疗效：治疗2 h后，ROX指数大于4.88提示有效，而12 h后仍小于3.85则提示治疗失败.有研究指出，可通过ROX指数预测HFNC治疗能否成功^[6].但对于HFNC治疗时间大于12 h的重型NCP患者来说，治疗失败的风险尚不清楚.本研究对重庆市公共卫生医疗救治中心负压病区应用HFNC治疗重型NCP患者的临床效果进行了回顾性分析.

1. 材料与方法

1.1. 研究对象

选取2020年1月24日-2月23日入住重庆市公共卫生医疗救治中心负压病区、符合重型NCP诊断标准并接受HFNC治疗的全部病例进行分析.重型NCP诊断标准符合文献[2]，有发热、咳嗽等症状，具有典型的NCP影像学特征且新型冠状病毒核酸阳性，同时满足以下任何一条：①出现气促，呼吸频率(respiratory rate，RR)≥30次/分；②静息状态下，指脉氧饱和度(SaO₂)≤93%；③动脉血氧分压(PaO₂)/吸入氧浓度(FiO₂)≤300 mmHg(1 mmHg=0.133 kPa).

1.2. 资料收集

通过电子病历数据库及微生物实验室数据库，回顾性收集全部研究对象的临床资料，包括：①一般项目患者年龄、性别、基础疾病、RR和SaO₂；②辅助检查入科时，CD4+绝对值、PaO₂和FiO₂，并计算不同时间点的ROX指数(定义为SaO₂/FiO₂与RR的比值)；③患者转归继续HFNC或给予NIV或有创机械通气(Invasive mechanical ventilation，IMV).

1.3. 数据处理

用SPSS 19.0统计软件处理数据，计量资料以平均数±标准差(x±s)表示，比较用t检验或重复测量设计的方差分析，然后对单因素分析结果有意义的因素采用Cox风险比例模型(cox proportional-hazardsmodel，也称Cox回归)进行分析，p＜0.05为差异有统计学意义.

3. 讨论

新型冠状病毒属于β属的冠状病毒，人群普遍易感，以发热、干咳和乏力为主要表现，且在发病一周后出现呼吸困难和(或)低氧血症，严重者可迅速发展为急性呼吸窘迫综合征、脓毒症休克、难以纠正的代谢性酸中毒、出凝血功能障碍及多器官功能衰竭等.文献[2]指出，当患者接受标准氧疗后呼吸窘迫和(或)低氧血症无法缓解时，可考虑使用HFNC或NIV.但本研究收治的20名重型NCP患者绝大多数都表现为CD4+绝对值降低，提示免疫功能受损.在免疫功能低下的患者中，HFNC相对于标准氧疗的优势尚未得到证实.改善氧合作用对所有急性低氧性呼吸功能衰竭(acute hypoxemic respiratory failure，AHRF)都有意义，在免疫功能低下的患者中更是如此.这些患者的低氧血症更严重，根据文献[2]，大多数患者都应给予HFNC治疗.但有研究表明，与标准氧疗相比，HFNC对于合并AHRF的免疫功能抑制患者并无显著获益^[5].

对于急性I型呼吸衰竭的患者，不延误必要的气管插管呼吸机辅助呼吸时机是HFNC氧疗支持中的关键. Frat等^[6]指出，当PaO₂/FiO₂＜200 mmHg时，无创通气可以更好地预防严重低氧血症的发生.本研究对HNFC治疗重型NCP失败的患者基线P/F进行Cox风险比例模型性分析的结果也是如此.换言之，HFNC可作为合并轻度AHRF(P/F为200~300 mmHg)的NCP患者有效的救治手段. ROX指数能够很好地预测HFNC的疗效：治疗2 h后ROX指数大于4.88提示有效，而12 h后仍小于3.85则提示治疗失败. Roca O等^[7]指出，在急性I型呼吸衰竭接受HFNC氧疗的过程中，ROX指数有助于判断患者是否需要气管插管呼吸机辅助呼吸的时机.因此，对于NCP合并急性呼吸窘迫综合征(acute respiratory distress syndrome，ARDS)的患者可用ROX指数筛选出风险很低和很高的那部分患者.本研究的单因素分析中成功组患者经HFNC治疗后2 h、12 h的ROX指数均大于失败组(p＜0.05)也印证了这一点.

本研究为回顾性分析，即以现在为结果回溯过去的研究方法，由于条件限制较少，且样本量较小，易产生选择偏倚和回忆偏倚，也不能计算重型NCP患者HFNC治疗的成功率并直接计算相对危险度，故HFNC治疗重型NCP患者的疗效还有待进一步研究确证.

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Analysis of the Efficiency of Treating 20 Critical Cases of 2019-nCoV with High-Flow Nasal Cannula Oxygen Therapy in Chongqing

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