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

Am J Respir Crit Care Med. 2020 Oct 15;202(8):1115-1124. doi: 10.1164/rccm.202006-2309OC.

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/cm3. 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.

Keywords: SARS-CoV-2; droplet; particle.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • Aerosols / administration & dosage*
  • Betacoronavirus*
  • COVID-19
  • Cannula
  • Coronavirus Infections / epidemiology
  • Coronavirus Infections / therapy*
  • Female
  • Healthy Volunteers
  • Humans
  • Male
  • Noninvasive Ventilation / methods
  • Oxygen Inhalation Therapy / methods*
  • Pandemics
  • Pneumonia, Viral / epidemiology
  • Pneumonia, Viral / therapy*
  • SARS-CoV-2

Substances

  • Aerosols