Modified N95 mask delivers high inspired oxygen concentrations while effectively filtering aerosolized microparticles.
OBJECTIVE
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 (F(I)O2) 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 F(I)O2s (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.


CONCLUSIONS
An N95 mask can be modified to administer a clinically equivalent FiO2 to a nonrebreathing mask while maintaining its filtration and isolation capabilities.
Mardimae
Alexandra
A
Department of Anesthesiology, University Health Network, Toronto, Ontario, Canada.
Slessarev
Marat
M
Han
Jay
J
Sasano
Hiroshi
H
Sasano
Nobuko
N
Azami
Takafumi
T
Fedorko
Ludwik
L
Savage
Tim
T
Fowler
Rob
R
Fisher
Joseph A
JA
D000336:Aerosols; D004189:Disaster Planning; D004196:Disease Outbreaks; D018562:Disease Transmission, Infectious / Q000517:prevention & control*; D004867:Equipment Design; D005374:Filtration / Q000295:instrumentation*; D006801:Humans; D007251:Influenza, Human / Q000453:epidemiology / Q000628:therapy / Q000635:transmission; D010100:Oxygen / Q000032:analysis; D010102:Oxygen Inhalation Therapy / Q000295:instrumentation*; D010316:Particle Size; D010356:Patient Isolation / Q000295:instrumentation*; D011446:Prospective Studies; D012134:Respiratory Protective Devices
D000336:Aerosols; D010100:Oxygen