Background Postextubation high-flow nasal cannula (HFNC) is used as a support therapy in high-risk patients in ICU. This study aimed to determine the effects of HFNC therapy on lung recruitment and overdistension assessed by electrical impedance tomography (EIT). Methods Twenty-four patients who received HFNC within 24 h after extubation were prospectively enrolled in this study. EIT was used to monitor regional lung ventilation distributions at baseline (conventional oxygen therapy) and three flow rate levels of HFNC therapy (20, 40, and 60 L/min). Change of end-expiratory lung impedance (ΔEELI), regional recruitment (recruited-pixels) and overdistension (overdistended-pixels), and lung strain change were determined by EIT. EIT images were equally divided into four ventral-to-dorsal horizontal regions of interest (ROIs 1, 2, 3, and 4). “Overdistension- by HFNC ” due to HFNC is defined as an increase of overdistened-pixels > 10 than baseline. Patients were divided into two groups: (1) high potential of recruitment (HPR), recruited-pixels > 10 pixels at 60 L/min than baseline, and (2) low potential of recruitment (LPR), recruited-pixels < 10 pixels at 60 L/min than baseline. Results When the flow rate gradually increased from baseline to 60 L/min, a significant and consistent increasing trend of global ΔEELI (%) ( p < 0.0001), recruited-pixels ( p < 0.001), and overdistended-pixels ( p = 0.101) was observed. Moreover, the increase of ΔEELI was mainly distributed in ROI2 ( p = 0.001) and ROI3 ( p < 0.0001). The HPR group (13/24 patients) had significantly higher recruited-pixels than the LPR group (11/24 patients) at 20, 40, and 60 L/min. There were no significant differences in PaO 2 /FiO 2 , ΔEELI (%), and overdistention pixels between the two groups. The HPR group had 13 patients in which no one had “overdistension- by HFNC ”, and the LPR group had 11 patients in which 4 patients had “overdistension- by HFNC ” (0/13 vs. 4/11, p = 0.017). Conclusions Using EIT could identify diverse effects of HFNC on lung regional ventilation in postextubation situations. Further study is required to validate using “HFNC effect” based on lung recruitment and overdistension by EIT in clinical practice. Trial registration The study was retrospectively registered at www.clinicaltrials.gov (no. NCT04245241 ).

中文翻译：

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拔管后高流量鼻导管治疗对高危患者肺复张及过度扩张的影响

背景拔管后高流量鼻插管 (HFNC) 被用作 ICU 高危患者的支持疗法。本研究旨在确定 HFNC 治疗对通过电阻抗断层扫描 (EIT) 评估的肺复张和过度扩张的影响。方法 前瞻性纳入拔管后 24 h 内接受 HFNC 的 24 例患者。EIT 用于监测基线（常规氧疗）和 HFNC 治疗的三个流速水平（20、40 和 60 L/min）时的区域肺通气分布。呼气末肺阻抗 (ΔEELI) 的变化、区域募集 (recruited-pixels) 和过度扩张 (overdistended-pixels) 和肺应变变化由 EIT 确定。EIT 图像被平均分为四个腹到背水平感兴趣区域（ROI 1、2、3 和 4）。由于 HFNC 导致的“HFNC 过度扩张”被定义为过度扩张像素比基线增加 > 10。患者被分为两组：(1) 高募集潜力 (HPR)，在 60 L/min 比基线时募集像素 > 10 像素，以及 (2) 低募集潜力 (LPR)，募集像素 < 10 像素60 L/min 比基线。结果当流速从基线逐渐增加到 60 L/min 时，整体 ΔEELI (%) ( p < 0.0001)、募集像素 ( p < 0.001) 和过度膨胀像素 ( p = 0.101 ） 被观测到。此外，ΔEELI的增加主要分布在ROI2（p=0.001）和ROI3（p<0.0001）。在 20、40 和 60 L/min 时，HPR 组（13/24 名患者）的募集像素明显高于 LPR 组（11/24 名患者）。两组之间的 PaO 2 /FiO 2 、ΔEELI (%) 和过度膨胀像素没有显着差异。HPR 组 13 例患者中没有“HFNC 过度扩张”，LPR 组 11 例患者中 4 例患者“HFNC 过度扩张”（0/13 vs. 4/11，p = 0.017） . 结论 使用 EIT 可以确定 HFNC 对拔管后肺区域通气的不同影响。需要进一步的研究来验证在临床实践中使用基于 EIT 肺募集和过度扩张的“HFNC 效应”。试验注册 该研究在 www.clinicaltrials.gov（编号 NCT04245241）上进行了回顾性注册。LPR 组有 11 名患者，其中 4 名患者患有“HFNC 引起的过度扩张”（0/13 对 4/11，p = 0.017）。结论 使用 EIT 可以确定 HFNC 对拔管后肺区域通气的不同影响。需要进一步的研究来验证在临床实践中使用基于 EIT 肺募集和过度扩张的“HFNC 效应”。试验注册 该研究在 www.clinicaltrials.gov（编号 NCT04245241）上进行了回顾性注册。LPR 组有 11 名患者，其中 4 名患者出现“HFNC 引起的过度扩张”（0/13 对 4/11，p = 0.017）。结论 使用 EIT 可以确定 HFNC 对拔管后肺区域通气的不同影响。需要进一步的研究来验证在临床实践中使用基于 EIT 肺募集和过度扩张的“HFNC 效应”。试验注册 该研究在 www.clinicaltrials.gov（编号 NCT04245241）上进行了回顾性注册。