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Assessment of dispersion of airborne particles of oral/nasal fluid by high flow nasal cannula therapy
medRxiv - Respiratory Medicine Pub Date : 2020-05-27 , DOI: 10.1101/2020.05.14.20102517
Mark C Jermy , Callum JT Spence , Robert Kirton , Jane F O'Donnell , Natalia Kabaliuk , Sally Gaw , Yannan Jiang , Zulkhairi Zainol Abidin , Ronald L Dougherty , Philip Rowe , Anjula Mahaliyana , Amelia Gibbs , Sally Roberts

Background Nasal High Flow (NHF) therapy delivers flows of heated humidified gases up to 60 LPM (litres per minute) via a nasal cannula. Particles of oral/nasal fluid released by patients undergoing NHF therapy may pose a cross-infection risk, which is a potential concern for treating COVID-19 patients. Methods Liquid particles within the exhaled breath of healthy participants were measured with two protocols: (1) high speed camera imaging and counting exhaled particles under high magnification (6 participants) and (2) measuring the deposition of a chemical marker (riboflavin-5-monophosphate) at a distance of 100 and 500 mm on filter papers through which air was drawn (10 participants). The filter papers were assayed with HPLC. Breathing conditions tested included quiet (resting) breathing and vigorous breathing (which here means nasal snorting, voluntary coughing and voluntary sneezing). Unsupported (natural) breathing and NHF at 30 and 60 LPM were compared. Results (1) Imaging: During quiet breathing, no particles were recorded with unsupported breathing or 30 LPM NHF (detection limit for single particles 33 microns). Particles were detected in 2 of 6 participants at 60 LPM quiet breathing at approximately 10% of the rate caused by unsupported vigorous breathing. Unsupported vigorous breathing released the greatest numbers of particles. Vigorous breathing with NHF at 60 LPM, released half the number of particles compared to vigorous breathing without NHF. (2) Chemical marker tests: No oral/nasal fluid was detected in quiet breathing without NHF (detection limit 0.28 microlitres/m3). In quiet breathing with NHF at 60 LPM, small quantities were detected in 4 out of 29 quiet breathing tests, not exceeding 17 microlitres/m3. Vigorous breathing released 200-1000 times more fluid than the quiet breathing with NHF. The quantities detected in vigorous breathing were similar whether using NHF or not. Conclusion During quiet breathing, 60 LPM NHF therapy may cause oral/nasal fluid to be released as particles, at levels of tens of microlitres per cubic metre of air. Vigorous breathing (snort, cough or sneeze) releases 200 to 1000 times more oral/nasal fluid than quiet breathing. During vigorous breathing, 60 LPM NHF therapy caused no statistically significant difference in the quantity of oral/nasal fluid released compares to unsupported breathing. NHF use does not increase the risk of dispersing infectious aerosols above the risk of unsupported vigorous breathing. Standard infection prevention and control measures should apply when dealing with a patient who has an acute respiratory infection, independent of which, if any, respiratory support is being used.

中文翻译:

高流量鼻导管疗法评估口腔/鼻液中空气传播颗粒的分散性

背景鼻高流量(NHF)疗法通过鼻导管输送高达60 LPM(升/分钟)的加热湿气。接受NHF治疗的患者释放的口腔/鼻液颗粒可能构成交叉感染的风险,这是治疗COVID-19患者的潜在问题。方法采用两种方案测量健康参与者呼出气中的液体颗粒:(1)高速相机成像并在高放大倍数下计数呼出颗粒(6个参与者);(2)测量化学标记物(核黄素5-单磷酸盐)在滤纸上以100和500毫米的距离抽吸空气(10名参与者)。滤纸用HPLC测定。测试的呼吸条件包括安静(休息)呼吸和剧烈呼吸(此处表示鼻吸气,自愿咳嗽和自愿打喷嚏)。比较了无支撑(自然)呼吸和30和60 LPM的NHF。结果(1)成像:在安静的呼吸过程中,没有记录到无支撑呼吸或30 LPM NHF(33微米单个颗粒的检出限)的颗粒。6个参与者中有2个在60 LPM安静呼吸时检测到颗粒,其速率约为无支撑剧烈呼吸所导致的速率的10%。不支持的剧烈呼吸会释放最多数量的颗粒。与没有NHF的剧烈呼吸相比,以60 LPM的NHF剧烈呼吸释放的颗粒数量减少了一半。(2)化学标志物测试:在没有NHF的安静呼吸中未检测到口腔/鼻液(检测极限为0.28微升/立方米)。以60 LPM的NHF安静呼吸时,在29个安静的呼吸测试中,有4个检测到少量,不超过17微升/立方米。剧烈呼吸释放的液体比使用NHF进行的安静呼吸多200-1000倍。无论是否使用NHF,剧烈呼吸中检测到的量均相似。结论在安静的呼吸过程中,60 LPM NHF疗法可能导致口腔/鼻液以微粒的形式释放,每立方米空气数十微升。剧烈呼吸(打s,咳嗽或打喷嚏)释放的口腔/鼻液比安静呼吸多200至1000倍。在剧烈呼吸期间,与无支持的呼吸相比,60 LPM NHF治疗不会导致口腔/鼻液释放量的统计学显着差异。使用NHF不会增加传播传染性气溶胶的风险,而不是不支持剧烈呼吸的风险。
更新日期:2020-05-27
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