Annals of Emergency Medicine
Volume 48, Issue 4 , Pages 391-399.e2, October 2006

Modified N95 Mask Delivers High Inspired Oxygen Concentrations While Effectively Filtering Aerosolized Microparticles

  • Alexandra Mardimae, Hon BSc

      Affiliations

    • Department of Anesthesiology, University Health Network, Toronto, Ontario, Canada
    • Department of Physiology, University of Toronto, Toronto, Ontario, Canada
    • ,
  • Marat Slessarev, MSc

      Affiliations

    • Department of Anesthesiology, University Health Network, Toronto, Ontario, Canada
    • Department of Physiology, University of Toronto, Toronto, Ontario, Canada
    • ,
  • Jay Han, Hon BSc

      Affiliations

    • Department of Anesthesiology, University Health Network, Toronto, Ontario, Canada
    • Department of Physiology, University of Toronto, Toronto, Ontario, Canada
    • ,
  • Hiroshi Sasano, MD

      Affiliations

    • Department of Anesthesiology and Medical Crisis Management, Nagoya City University Graduate School of Medical Sciences, Nagoya, Japan
    • ,
  • Nobuko Sasano, MD, PhD

      Affiliations

    • Department of Anesthesiology and Medical Crisis Management, Nagoya City University Graduate School of Medical Sciences, Nagoya, Japan
    • ,
  • Takafumi Azami, MD, PhD

      Affiliations

    • Department of Anesthesiology and Medical Crisis Management, Nagoya City University Graduate School of Medical Sciences, Nagoya, Japan
    • ,
  • Ludwik Fedorko, MD, PhD

      Affiliations

    • Department of Anesthesiology, University Health Network, Toronto, Ontario, Canada
    • ,
  • Tim Savage, BSc

      Affiliations

    • Department of Occupational Health and Safety, University Health Network, Toronto, Ontario, Canada
    • ,
  • Rob Fowler, MD, MSc

      Affiliations

    • Interdepartmental Division of Critical Care Medicine, University of Toronto, Sunnybrook and Women’s College Health Sciences Centre, Toronto, Ontario, Canada
    • ,
  • Joseph A. Fisher, MD

      Affiliations

    • Department of Anesthesiology, University Health Network, Toronto, Ontario, Canada
    • Department of Physiology, University of Toronto, Toronto, Ontario, Canada
    • Corresponding Author InformationAddress for correspondence: Joseph A. Fisher MD, Toronto General Hospital 7EN-242, 200 Elizabeth St, Toronto, Ontario, Canada M5G 2C4; 416-340-4800 ext 3071, fax 416-340-4448

Received 11 March 2006; received in revised form 11 April 2006 and 10 May 2006; accepted 12 June 2006.

Study 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 (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.

 Reprints not available from the authors.

PII: S0196-0644(06)00942-5

doi:10.1016/j.annemergmed.2006.06.039

Annals of Emergency Medicine
Volume 48, Issue 4 , Pages 391-399.e2, October 2006

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