Assessing Aerosol Generation During Different Oxygen Delivery Methods

Oxygen delivery using either humidified high flow nasal cannula or noninvasive positive pressure ventilation does not appear to increase aerosol generation from the respiratory tract, according to the results of a recent study published in the American Journal of Respiratory and Critical Care Medicine.

Aerosol generation from the respiratory tract of healthy participants was measured during normal breathing, talking, deep breathing, and coughing in a negative pressure room while using various oxygen delivery methods. Measurements were taken using an aerodynamic particle spectrometer. Aerosol generation was compared between modalities. Tested modalities included non-humidified nasal cannula, face mask, heated and humidified high flow nasal cannula, and noninvasive positive pressure ventilation.

A total of 10 healthy participants (median age, 35 years) were enrolled and completed testing using the various oxygen delivery modalities. Particles generated had a median concentration of 0.041 to 0.168 particles/cm³, and the median diameter ranged from 1.01 to 1.53 μm. Overall, the act of coughing significantly increased the number of particles measured. However, for both humidified high flow nasal cannula and noninvasive positive pressure ventilation, the aerosol concentration did not significantly increase during normal breathing, talking, deep breathing, or coughing.

Because the study size was small and included only healthy participants without active pulmonary disease, the applicability of these results to the ongoing coronavirus disease 2019 pandemic may be limited. Future research examining aerosol generation with high-flow nasal cannula oxygen and noninvasive positive pressure ventilation in active pulmonary disease is necessary. 

“Oxygen delivery modalities of humidified high flow nasal cannula and non-invasive 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,” the study authors wrote. “Aerosol generation is influenced more by breathing pattern and coughing than the mode of oxygen therapy applied.”

Reference

Gaeckle NT, Lee J, Park Y, Kreykes G, Evans MD, Hogan CJ Jr. Aerosol generation from the respiratory tract with various modes of oxygen delivery. Am J Respir Crit Care Med. Published online August 21, 2020.  doi:10.1164/rccm.202006-2309OC