Aerosol Generation from the Respiratory Tract with Various Modes of Oxygen Delivery

Abstract

Rationale: Aerosol generation with modes of oxygen therapy such as high-flow nasal cannula and noninvasive positive-pressure ventilation is a concern for healthcare workers during the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) pandemic. The amount of aerosol generation from the respiratory tract with these various oxygen modalities is unknown. Objectives: To measure the size and number concentration of particles and droplets generated from the respiratory tract of humans exposed to various oxygen delivery modalities. Methods: Ten healthy participants with no active pulmonary disease were enrolled. Oxygen modalities tested included nonhumidified nasal cannula, face mask, heated and humidified high-flow nasal cannula, and noninvasive positive-pressure ventilation. Aerosol generation was measured with each oxygen mode while participants performed maneuvers of normal breathing, talking, deep breathing, and coughing. Testing was conducted in a negative-pressure room. Particles with a diameter between 0.37 and 20 μm were measured using an aerodynamic particle spectrometer. Measurements and Main Results: Median particle concentration ranged from 0.041 to 0.168 particles/cm 3 . Median diameter ranged from 1.01 to 1.53 μm. Cough significantly increased the number of particles measured. Measured aerosol concentration did not significantly increase with the use of either humidified high-flow nasal cannula or noninvasive positive-pressure ventilation. This was the case during normal breathing, talking, deep breathing, and coughing. Conclusions: Oxygen delivery modalities of humidified high-flow nasal cannula and noninvasive positive-pressure ventilation do not increase aerosol generation from the respiratory tract in healthy human participants with no active pulmonary disease measured in a negative-pressure room.

Non-invasive respiratory support paths in hospitalized patients with COVID-19: proposal of an algorithm

“…Recently, several publications report that NIRT are not actually aerosol generators, but aerosol dispersers. 8 And so, with the appropriate PPE, 4 , 5 and in the hands of experienced teams, it’s possible to reduce the intubation rate without seriously increasing the risk of nosocomial infections.…”

THRIVE: five years on and into the COVID-19 era

“…40 Higher gas flow rates generated more droplets, but NHFO actually reduced droplet/aerosol dispersion during sneezing, as the inward gas flow opposed nasal expiration. Gaeckle and colleagues 39 reported greater levels of aerosol and droplet generation with coughing but that NHFO did not increase this. These limited studies suggest NHFO may reduce droplet dispersion during sneezing and does not increase droplet dispersion during coughing compared with other oxygen delivery devices.…”

“…38 A study of aerosol generation in healthy volunteers during normal breathing, found that NHFO did not increase aerosol generation compared with other modes of oxygen delivery (4 L min -1 simple nasal cannula (0.060 particles cm -3 ), 15 L min -1 face mask (0.059 particles cm -3 ), NHFO 30 L min -1 (0.046 particles cm -3 ), NHFO 50 L min -1 (0.041 particles cm -3 ), NIV 12/5 (0.056 particles cm -3 ) and NIV 20/10 cmH 2 O (0.057 particles cm -3 )). 39…”

COVID-19 acquisition risk among ICU nursing staff with patient-driven use of aerosol-generating respiratory procedures and optimal use of personal protective equipment

“…We hypothesised that optimal use of potentially aerosol-generating procedures does not increase the risk of COVID-19 in HCWs when strict personal protection equipment (PPE) is applied ( Jansson et al, 2020 , Gaeckle et al, 2020 ).…”

“…The protective effect of working at the COVID-ICU appears clinically meaningless, as such infection risk seems mainly influenced by circumstances outside the hospital. Even when the degree of aerosolisation is uncertain ( Gaeckle et al, 2020 ), the need for adequate HCW protection remains mandatory to ensure their safety.…”