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Respirator Tolerance in Health Care Workers
To the Editor: Anticipated respirator intolerance and supply shortages during future influenza pandemics prompted the Institute of Medicine to review respirator use in health care workers1 and consider whether disposable models could be reused or modified for reuse.2 One option involves placing a medical mask over a disposable respirator to diminish contamination and attrition.1 However, little is known about the workplace tolerability of respirators commonly worn by health care workers, who may be called on to wear respiratory protection for the duration of their work shifts for several consecutive weeks during a pandemic.3-4 We estimated the length of time health care workers would tolerate wearing commonly used respirators while performing their typical occupational duties.
Methods
Participants were 27 volunteers (mean [SD] age, 48 [11] years; range, 25-65 years; 15 women) among approximately 225 health care workers employed by the local Veterans Health System who were approached. The inclusion criterion was having worn a respirator in the context of duties at least once; all participants were accustomed to wearing N95 respirators (filters  95% of particles approximately 0.3 µm in size) for brief periods. Exclusion criteria included systemic disease or pregnancy. The sample comprised 16 nurses, 2 nurse practitioners, 4 nurse technicians, 2 telemetry technicians, 2 respiratory therapists, and 1 clerical assistant from the intensive care unit (n = 15), emergency department (n = 6), and medical/surgical ward (n = 6). Each provided written informed consent, underwent a prestudy examination, and was fit-tested for each respirator. The study was approved by the local institutional review board.
In this unblinded multiple crossover study, before each work shift (intersession interval, 1 day) each participant was randomly assigned a respirator ensemble (Table 1) to wear as long as he or she was "willing to tolerate" the effects while performing typical occupational duties, not including interposed break periods (15 minutes at 2 and 6 hours; 30 minutes at 4 hours). Those who experienced intolerance before 8 hours reported up to 3 reasons for premature discontinuation.
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Table 1. Characteristics and Tolerability of Respiratory Protective Ensemblesa
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Sample size was chosen to achieve power of 0.8 or greater to detect a difference of 2 hours in median tolerance times. Kaplan-Meier estimates of survival were used for descriptive purposes. Tolerance time for the cup-shaped N95 was compared with a medical mask and with the N95 with an exhalation valve. The 2 respirators that had a medical mask placed over the respirator surface to protect against contamination were compared with the same respirators without a mask. An extended Cox model,5 which accounted for correlation between repeated measures within participant, was used to compare the time to doff among respirators by controlling for the effects of sex and age. SAS 9.1 (SAS Institute, Cary, North Carolina) was used for the analyses. The Bonferroni step-down method6 was used to adjust the P values for 2-sided tests to account for multiple tests.
Results
Each participant wore all 8 respirators except 1 who failed the duckbill N95 fit test. No sequence or period effects were found. Tolerance time varied by respirator model (Table 1). Women were significantly more likely than men to experience intolerance before 8 hours (hazard ratio, 1.97; 95% confidence interval, 1.02-3.75; P = .04). Participants discontinued wearing the respirator ensembles before 8 hours in 126 of 215 total sessions (59%), reporting a variety of reasons for intolerance, including communication interference (Table 2).
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Table 2. Reported Reasons for Discontinuing Respirator Use Before 8 Hours Among 27 Participantsa
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Comment
A large percentage of participants were unwilling to wear the respirator ensembles for the entire 8-hour work shift, even with interposed break periods. No respirator was ideal: users of disposable models frequently experienced facial heat and pressure, and users of reusable models frequently experienced communication interference. Wearing a cup-shaped N95 without an exhalation valve was associated with more intolerance than a similar model with a valve. Study limitations include small sample size, a single study location, and a setting that only simulated a pandemic scenario. However, these findings suggest that new respirator designs may be necessary to improve tolerability.
Author Contributions: Dr Radonovich had full access to all of the data in the study and takes responsibility for the integrity of the data and the accuracy of the data analysis.
Study concept and design: Radonovich, Cheng, Shenal, Hodgson, Bender.
Acquisition of data: Radonovich.
Analysis and interpretation of data: Radonovich, Cheng, Hodgson, Bender.
Drafting of the manuscript: Radonovich, Cheng, Hodgson.
Critical revision of the manuscript for important intellectual content: Radonovich, Cheng, Shenal, Hodgson, Bender.
Statistical analysis: Cheng.
Obtained funding: Radonovich, Shenal.
Administrative, technical, or material support: Radonovich.
Study supervision: Radonovich, Bender.
Financial Disclosures: None reported.
Funding/Support: This study was funded by the US Department of Veterans Affairs.
Role of the Sponsor: The sponsor was engaged in the study design but played no role in the conduct of the study; in the collection, management, analysis, and interpretation of the data; or in the preparation, review, and approval of the manuscript.
Disclaimer: The views, opinions, and findings contained in this report are those of the authors and do not necessarily represent the official position or policy of the North Florida/South Georgia Veterans Health System, the Office of Public Health and Environmental Hazards, the US Department of Veterans Affairs, or the University of Florida or other employers or affiliates.
Additional Contributions: Helen Dunn, MSN, Malcom Randall VA Medical Center, and Elizabeth Franco, RN, Malcom Randall VA Medical Center, coordinated the study and received compensation. Parker Small, MD, University of Florida, provided review and guidance and did not receive compensation.
Lewis J. Radonovich Jr, MD
lewis.radonovich{at}va.gov
Malcom Randall Veterans Affairs Medical Center
Gainesville, Florida
Jing Cheng, PhD
University of Florida College of Medicine
Gainesville
Brian V. Shenal, PhD
Veterans Affairs Medical Center
Salem, Virginia
Michael Hodgson, MD, MPH
Veterans Health Administration
Washington, DC
Bradley S. Bender, MD
Malcom Randall Veterans Affairs Medical Center
Gainesville
1. Goldfrank LR, ed, Liverman CT, ed. Preparing for an Influenza Pandemic: Personal Protective Equipment for Healthcare Workers: Institute of Medicine Report. Washington, DC: National Academies Press; 2008.
2. Reusability of Facemasks During an Influenza Pandemic: Facing the Flu: Institute of Medicine Report. Washington, DC: National Academies Press; 2006.3. Siegel JD, Rhinehart E, Jackson M, Chiarello L, the Healthcare Infection Control Practices Advisory Committee. Guideline for Isolation Precautions: Preventing Transmission of Infectious Agents in Healthcare Settings 2007. http://www.cdc.gov/ncidod/dhqp/pdf/guidelines/Isolation2007.pdf. Accessed December 1, 2008.4. Guidance on Preparing Workplaces for an Influenza Pandemic [OSHA 3327-02N 2007]. Occupational Safety and Health Administration. http://www.osha.gov/Publications/influenza_pandemic.html. Accessed December 1, 2008.5. Lin DY. Cox regression analysis of multivariate failure time data: the marginal approach. Stat Med. 1994;13(21):2233-2247.
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6. Hochberg YT, Tamhane AC. Multiple Comparison Procedures. New York, NY: John Wiley & Sons; 1987.
Letters Section Editor: Robert M. Golub, MD, Senior Editor.
JAMA. 2009;301(1):36-38.
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