In a pandemic, hypoxic patients will require an effective oxygen (O2) delivery mask that protects them from inhaling aerosolized particles produced by others, as well as protecting the health care provider from exposure from the patient. We modified an existing N95 mask to optimize O2 supplementation while maintaining respiratory isolation.
Methods
An N95 mask was modified to deliver O2 by inserting a plastic manifold consisting of a 1-way inspiratory valve, an O2 inlet and a gas reservoir. In a prospective repeated-measures study, we studied 10 healthy volunteers in each of 3 phases, investigating (1) the fractional inspiratory concentrations of O2 (FIO2) delivered by the N95 O2 mask, the Hi-Ox80 O2 mask, and the nonrebreathing mask during resting ventilation and hyperventilation, each at 3 O2 flow rates; (2) the ability of the N95 mask, the N95 O2 mask, and the nonrebreathing mask to filter microparticles from ambient air; and (3) to contain microparticles generated inside the mask.
Results
The FIO2s (median [range]) delivered by the Hi-Ox80 O2 mask, the N95 O2 mask, and the nonrebreathing mask during resting ventilation, at 8 L/minute O2 flow, were 0.90 (0.79 to 0.96), 0.68 (0.60 to 0.85), and 0.59 (0.52 to 0.68), respectively. During hyperventilation, the FiO2s of all 3 masks were clinically equivalent. The N95 O2 mask, but not the nonrebreathing mask, provided the same efficiency of filtration of internal and external particles as the original N95, regardless of O2 flow into the mask.
Conclusion
An N95 mask can be modified to administer a clinically equivalent FiO2 to a nonrebreathing mask while maintaining its filtration and isolation capabilities.
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Supervising editor: Jonathan L. Burstein, MD
Author contributions: HS, NS, and TA initiated the study and initial proof of concept. AM, MS, JH, HS, NS, TA, LF, TS, and RF conducted study design. AM, MS, JH, LF, and TS conducted data gathering. AM, MS, and JH analyzed data. AM, MS, and JH prepared the article. RF and JAF were the major contributors to the article. LF and TS contributed to the article. JAF was the study coordinator and supervisor. JAF takes responsibility for the paper as a whole.
Funding and support: MS, HS, NS, TA, LF, and JAF are part of a group organized under the auspices of the University Health Network, Toronto, Ontario, Canada. The group has patented one of the devices described in this manuscript.