Abstract：
OBJECTIVE: High-flow nasal cannula (HFNO) reduces the need for invasive mechanical ventilation in COVID-19 patients with hypoxemic-respiratory failure. During HFNO entrainment of room air dilutes the delivered fractional inspiratory oxygen (FiO2), thereby preventing improvement in oxygenation. The placement of a mask over HFNO to improve oxygenation has provided conflicting results. We aimed to determine and compare the effect of placing various mask types over HFNO on oxygen saturation (SPO2).
METHODS: In this prospective physiological study 40 patients with COVID-19-associated hypoxemic respiratory failure on HFNO with O2 concentration <92% were included. The effect of placing different masks over HFNO on oxygenation, respiratory rate, heart rate, blood pressure, patient comfort, and partial pressure of carbon dioxide level (pCO2) was recorded after a prespecified time interval.
RESULTS: We observed a significantly higher mean SPO2 and lower mean respiratory rate on using various study masks over HFNO compared to HFNO alone. On comparing various mask types, the use of N95 masks and nonrebreather (NRB) masks with O2 showed a significant increase in O2 concentration and reduction in respiratory rate compared to surgical mask (SM) and NRB without O2. The proportion of patients who achieved SPO2 of >92% was higher with the use of N95 masks (47.5%) or NRB with O2 (45%) over HFNO compared to SM (35%) and NRB without O2 (35%). No significant change was observed in heart rate, blood pressure, and CO2 level with the use of any mask over HFNO.
CONCLUSIONS: This study demonstrates improvement in oxygenation and reduction in respiratory rate with the use of various masks over HFNO in patients of COVID-19-related hypoxemic-respiratory-failure. Significantly greater benefit was achieved with the use of N95 or NRB with O2 compared to SM or NRB without O2.
METHODS: In this prospective physiological study 40 patients with COVID-19-associated hypoxemic respiratory failure on HFNO with O2 concentration <92% were included. The effect of placing different masks over HFNO on oxygenation, respiratory rate, heart rate, blood pressure, patient comfort, and partial pressure of carbon dioxide level (pCO2) was recorded after a prespecified time interval.
RESULTS: We observed a significantly higher mean SPO2 and lower mean respiratory rate on using various study masks over HFNO compared to HFNO alone. On comparing various mask types, the use of N95 masks and nonrebreather (NRB) masks with O2 showed a significant increase in O2 concentration and reduction in respiratory rate compared to surgical mask (SM) and NRB without O2. The proportion of patients who achieved SPO2 of >92% was higher with the use of N95 masks (47.5%) or NRB with O2 (45%) over HFNO compared to SM (35%) and NRB without O2 (35%). No significant change was observed in heart rate, blood pressure, and CO2 level with the use of any mask over HFNO.
CONCLUSIONS: This study demonstrates improvement in oxygenation and reduction in respiratory rate with the use of various masks over HFNO in patients of COVID-19-related hypoxemic-respiratory-failure. Significantly greater benefit was achieved with the use of N95 or NRB with O2 compared to SM or NRB without O2.
摘要：
目的：高流量鼻插管（HFNO）可降低COVID-19伴低氧血症性呼吸衰竭患者的有创机械通气需求。在HFNO夹带室内空气期间，稀释了输送的部分吸入氧气(FiO2)，从而防止氧合的改善。在HFNO上放置面罩以改善氧合提供了矛盾的结果。我们旨在确定和比较在HFNO上放置各种面罩对氧饱和度（SPO2）的影响。
方法：在这项前瞻性生理研究中，纳入了40例O2浓度<92%的HFNO与COVID-19相关的低氧性呼吸衰竭患者。在HFNO上放置不同的面罩对氧合的影响，呼吸频率,心率,血压,患者舒适度,在预定的时间间隔后记录二氧化碳分压水平（pCO2）。
结果：我们观察到，与单独使用HFNO相比，在使用各种研究面罩时，使用HFNO的平均SPO2和平均呼吸频率明显较高。在比较各种遮罩类型时，与不含O2的外科面罩（SM）和NRB相比，使用N95面罩和无呼吸呼吸（NRB）面罩的O2浓度显着增加，呼吸频率降低。与SM（35％）和不含O2的NRB（35％）相比，使用N95面罩（47.5％）或具有O2的NRB（45％）高于HFNO的SPO2>92％的患者比例更高。心率无明显变化,血压,和CO2水平与使用任何口罩在HFNO。
结论：这项研究表明，在COVID-19相关的低氧血症性呼吸衰竭患者中，使用各种口罩相对于HFNO可以改善氧合并降低呼吸频率。与没有O2的SM或NRB相比,使用具有O2的N95或NRB实现了显著更大的益处。
方法：在这项前瞻性生理研究中，纳入了40例O2浓度<92%的HFNO与COVID-19相关的低氧性呼吸衰竭患者。在HFNO上放置不同的面罩对氧合的影响，呼吸频率,心率,血压,患者舒适度,在预定的时间间隔后记录二氧化碳分压水平（pCO2）。
结果：我们观察到，与单独使用HFNO相比，在使用各种研究面罩时，使用HFNO的平均SPO2和平均呼吸频率明显较高。在比较各种遮罩类型时，与不含O2的外科面罩（SM）和NRB相比，使用N95面罩和无呼吸呼吸（NRB）面罩的O2浓度显着增加，呼吸频率降低。与SM（35％）和不含O2的NRB（35％）相比，使用N95面罩（47.5％）或具有O2的NRB（45％）高于HFNO的SPO2>92％的患者比例更高。心率无明显变化,血压,和CO2水平与使用任何口罩在HFNO。
结论：这项研究表明，在COVID-19相关的低氧血症性呼吸衰竭患者中，使用各种口罩相对于HFNO可以改善氧合并降低呼吸频率。与没有O2的SM或NRB相比,使用具有O2的N95或NRB实现了显著更大的益处。
