Dear Editor, Use of high-flow nasal cannula (HFNC) is common in critically ill patients with or at risk of respiratory failure. Its benefits include accurate delivery of the set fraction of inspired oxygen (FiO2), carbon dioxide washout from nasopharyngeal dead space, provision of small degree of positive end-expiratory pressure, and improved tolerance due to the comfortable interface [1–3]. To continuously deliver flows up to 60 l/min, inspired gas is actively conditioned through a heated humidifier, which increases gas temperature and absolute humidity up to 37 °C and 44 mgH2O/l. Airway warming (i.e., respiratory insulation) is a technique previously described to treat hypothermia [4]. In the lungs, the surface available for heat exchange is that of pulmonary havens, with a total area of about 100– 140 m. Moreover, inhalation of heated air yields vasodilation of alveolar capillaries, which further increases the surface for heat exchange between the blood and alveolar gas. Full humidification of inhaled air enhances heat transfer and conduction [4, 5]. Over a 6-month period (October 2018–March 2019), we applied, for clinical purposes, HFNC with no oxygen supplementation to 4 patients (3 females, median [interquartile range] age 51 [67–86] years), who were admitted to the emergency department of our institution with stage 1–2 primary hypothermia (i.e., prolonged exposure to cold environment) [6]. All patients were fully awake, hemodynamically stable, and had no respiratory distress nor gas exchange impairment. HFNC was administered through the AIRVO 2 device (Fisher and Paykel healthcare, New Zealand) or by a gas-compressed mechanical ventilator (EvitaXL or EvitaInfinity, Draeger, Lubeck, Germany) through a heated humidifier (MR860, Fisher and Paykel Healthcare, New Zealand): gas flow was set at 50–60 l/min, humidification chamber at 37 °C, and FiO2 at 21%. In all subjects, body temperature was recorded every 15 min through a dedicated urinary catheter (Teleflex, Annacotty, Limerick, Ireland). We retrospectively compared these patients with 4 matched control subjects (2 females, median [interquartile range] age 70 [52–80] years) who were admitted to the emergency department due to primary hypothermia in the same time period, did not receive HFNC, had no respiratory failure, and had body temperature recorded with the same technique: 1:1 matching was performed solely on the basis of body temperature at admission ± 0.2 °C. As a standard of care in our institution, all patients received treatment with warm blankets and heated crystalloid infusion, and the treatment was continued to achieve a core body temperature of 36 °C. All patients provided informed consent to data analysis and publication. The median [interquartile range] body temperature at admission was 32.4 [32–32.9] °C in both groups. In the initial 5 h of treatment, the median crystalloid infusion was 3.3 l [2.6–3.8] in patients treated with HFNC and 3.3 l [2.3–4.3] in control subjects. The median time to rewarming (defined as sustained body temperature ≥ 35 °C) was shorter in patients treated with HFNC: 120 [120–165] versus 345 [218–405] minutes (Mann-Whitney p = 0.026). In the initial 5 h of treatment, the body temperature was

中文翻译：

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用于体温过低时身体复温的高流量鼻插管

亲爱的编辑，高流量鼻插管 (HFNC) 在患有呼吸衰竭或有呼吸衰竭风险的危重患者中很常见。它的好处包括准确输送设定的吸入氧 (FiO2) 分数、从鼻咽死腔中冲洗二氧化碳、提供小程度的呼气末正压，以及由于舒适的界面而提高了耐受性 [1-3]。为了连续输送高达 60 l/min 的流量，吸入的气体通过加热加湿器进行主动调节，将气体温度和绝对湿度提高到 37 °C 和 44 mgH2O/l。气道加温（即呼吸隔离）是一种先前描述的用于治疗体温过低的技术 [4]。在肺中，可供热交换的表面是肺港，总面积约为100-140 m。而且，吸入热空气会使肺泡毛细血管扩张，这进一步增加了血液和肺泡气体之间的热交换面积。吸入空气的充分加湿可增强热传递和传导 [4, 5]。在 6 个月的时间里（2018 年 10 月至 2019 年 3 月），出于临床目的，我们向 4 名患者（3 名女性，中位 [四分位距] 年龄 51 [67-86] 岁）应用了不补充氧气的 HFNC因 1-2 期原发性体温过低（即长期暴露于寒冷环境）而被送入我们机构的急诊科 [6]。所有患者均完全清醒，血流动力学稳定，无呼吸窘迫或气体交换障碍。HFNC 通过 AIRVO 2 设备（Fisher and Paykel Healthcare，新西兰）或通过气体压缩机械呼吸机（EvitaXL 或 EvitaInfinity，Draeger，Lubeck，德国）通过加热加湿器（MR860，Fisher and Paykel Healthcare，新西兰）：气流设定为 50–60 l/min， 37 °C 的加湿室和 21% 的 FiO2。在所有受试者中，通过专用导尿管（Teleflex, Annacotty, Limerick, Ireland）每 15 分钟记录一次体温。我们回顾性地将这些患者与 4 名匹配的对照受试者（2 名女性，中位 [四分位距] 年龄 70 [52-80] 岁）在同一时间段内因原发性体温过低而被送入急诊科，未接受 HFNC，没有呼吸衰竭，并使用相同的技术记录体温：仅根据入院时的体温 ± 0.2 °C 进行 1:1 匹配。作为我们机构的标准护理，所有患者都接受了温暖的毯子和加热晶体输液的治疗，并继续治疗以达到核心体温 36 °C。所有患者均知情同意数据分析和发表。两组入院时的中位 [四分位距] 体温均为 32.4 [32-32.9] °C。在最初的 5 小时治疗中，接受 HFNC 治疗的患者的晶体液中位输注量为 3.3 升 [2.6-3.8]，而对照组为 3.3 升 [2.3-4.3]。接受 HFNC 治疗的患者复温的中位时间（定义为持续体温 ≥ 35 °C）较短：120 [120-165] 分钟比 345 [218-405] 分钟（Mann-Whitney p = 0.026）。在治疗的最初 5 小时，体温为 所有患者均接受温暖的毯子和加热晶体输液治疗，并继续治疗，使核心体温达到 36 ℃。所有患者均知情同意数据分析和发表。两组入院时的中位 [四分位距] 体温均为 32.4 [32-32.9] °C。在最初的 5 小时治疗中，接受 HFNC 治疗的患者的晶体液中位输注量为 3.3 升 [2.6-3.8]，而对照组为 3.3 升 [2.3-4.3]。接受 HFNC 治疗的患者复温的中位时间（定义为持续体温 ≥ 35 °C）较短：120 [120-165] 分钟比 345 [218-405] 分钟（Mann-Whitney p = 0.026）。在治疗的最初 5 小时，体温为 所有患者均接受温暖的毯子和加热晶体输液治疗，并继续治疗，使核心体温达到 36 ℃。所有患者均知情同意数据分析和发表。两组入院时的中位 [四分位距] 体温均为 32.4 [32-32.9] °C。在最初的 5 小时治疗中，接受 HFNC 治疗的患者的晶体液中位输注量为 3.3 升 [2.6-3.8]，而对照组为 3.3 升 [2.3-4.3]。接受 HFNC 治疗的患者复温的中位时间（定义为持续体温 ≥ 35 °C）较短：120 [120-165] 分钟比 345 [218-405] 分钟（Mann-Whitney p = 0.026）。在治疗的最初 5 小时，体温为 所有患者均知情同意数据分析和发表。两组入院时的中位 [四分位距] 体温均为 32.4 [32-32.9] °C。在最初的 5 小时治疗中，接受 HFNC 治疗的患者的晶体液中位输注量为 3.3 升 [2.6-3.8]，而对照组为 3.3 升 [2.3-4.3]。接受 HFNC 治疗的患者复温的中位时间（定义为持续体温 ≥ 35 °C）较短：120 [120-165] 分钟比 345 [218-405] 分钟（Mann-Whitney p = 0.026）。在治疗的最初 5 小时，体温为 所有患者均知情同意数据分析和发表。两组入院时的中位 [四分位距] 体温均为 32.4 [32-32.9] °C。在最初的 5 小时治疗中，接受 HFNC 治疗的患者的晶体液中位输注量为 3.3 升 [2.6-3.8]，而对照组为 3.3 升 [2.3-4.3]。接受 HFNC 治疗的患者复温的中位时间（定义为持续体温 ≥ 35 °C）较短：120 [120-165] 分钟比 345 [218-405] 分钟（Mann-Whitney p = 0.026）。在治疗的最初 5 小时，体温为 8] 在接受 HFNC 治疗的患者中为 3.3 l [2.3–4.3] 在对照组中。接受 HFNC 治疗的患者复温的中位时间（定义为持续体温 ≥ 35 °C）较短：120 [120-165] 分钟比 345 [218-405] 分钟（Mann-Whitney p = 0.026）。在治疗的最初 5 小时，体温为 8] 在接受 HFNC 治疗的患者中为 3.3 l [2.3–4.3] 在对照组中。接受 HFNC 治疗的患者复温的中位时间（定义为持续体温 ≥ 35 °C）较短：120 [120-165] 分钟比 345 [218-405] 分钟（Mann-Whitney p = 0.026）。在治疗的最初 5 小时，体温为