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Surgical Mask May Be Comparable to N95 Respirator in Halting Flu Transmission CME/CE

News Author: Laurie Barclay, MD
CME Author: Charles P. Vega, MD

Authors and Disclosures

CME/CE Released: 10/05/2009; Valid for credit through 10/05/2010

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Target Audience

This article is intended for primary care clinicians, infectious disease specialists, and other specialists who care for patients at risk for infection with influenza.

Goal

The goal of this activity is to provide medical news to primary care clinicians and other healthcare professionals in order to enhance patient care.

Authors and Disclosures

Laurie Barclay, MD
freelance writer and reviewer, MedscapeCME
Disclosure: Laurie Barclay, MD, has disclosed no relevant financial relationships.

Brande Nicole Martin
is the News CME editor for Medscape Medical News.
Disclosure: Brande Nicole Martin has disclosed no relevant financial information.

Charles P. Vega, MD
Associate Professor and Residency Director, Department of Family Medicine, University of California-Irvine, Irvine California
Disclosure: Charles P. Vega, MD, has disclosed no relevant financial relationships.

Laurie E. Scudder, MS, NP
Accreditation Coordinator, Continuing Professional Education Department, MedscapeCME; Clinical Assistant Professor, School of Nursing and Allied Health, George Washington University, Washington, DC; Nurse Practitioner, School-Based Health Centers, Baltimore City Public Schools, Baltimore, Maryland
Disclosure: Laurie E. Scudder, MS, NP, has disclosed no relevant financial relationships.

Learning Objectives

Upon completion of this activity, participants will be able to:

1. Compare hand washing with soap and water vs the use of alcohol gels on potential transmission of influenza virus.
2. Compare surgical masks vs N95 respirators in the prevention of influenza.

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Physicians - maximum of 0.25 AMA PRA Category 1 Credit(s)™

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CME/CE Released: 10/05/2009; Valid for credit through 10/05/2010

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October 5, 2009 — Use of a surgical mask may not be inferior to the N95 respirator in halting influenza transmission in healthcare workers, according to the results of a noninferiority, randomized controlled trial published online October 1 and to be published in the November 4 print issue of the Journal of the American Medical Association.

"Data about the effectiveness of the surgical mask compared with the N95 respirator for protecting health care workers against influenza are sparse," write Mark Loeb, MD, MSc, from McMaster University in Hamilton, Ontario, Canada, and colleagues. "Given the likelihood that N95 respirators will be in short supply during a pandemic and not available in many countries, knowing the effectiveness of the surgical mask is of public health importance."

The goal of this study was to compare the surgical mask with the N95 respirator in protecting healthcare workers from influenza infection.

At 8 tertiary-care Ontario hospitals during the 2008 to 2009 influenza season, 446 nurses in emergency departments, medical units, and pediatric units were randomly assigned to use either a fit-tested N95 respirator or a surgical mask when caring for patients with febrile respiratory illness. Laboratory-confirmed influenza, measured by polymerase chain reaction or a 4-fold rise in hemagglutinin titers, was the main study endpoint.

Surgical mask efficacy was defined as being noninferior to the N95 respirator, with noninferiority defined as the lower limit of the 95% confidence interval (CI) for the reduction in incidence (N95 respirator minus surgical group) greater than −9%.

Of 478 nurses evaluated for eligibility from September 23 to December 8, 2008, 446 nurses were enrolled and randomized, with 225 assigned to use surgical masks and 221 to use N95 respirators. In the surgical mask group, influenza infection occurred in 50 nurses (23.6%) compared with 48 (22.9%) in the N95 respirator group (absolute risk difference, −0.73%; 95% CI, −8.8% to 7.3%; P = .86, with the lower confidence limit being inside the noninferiority limit of −9%). Noninferiority of the surgical mask was also shown for influenza A (H1N1).

"Among nurses in Ontario tertiary care hospitals, use of a surgical mask compared with an N95 respirator resulted in noninferior rates of laboratory-confirmed influenza," the study authors write. "Our findings apply to routine care in the health care setting. They should not be generalized to settings where there is a high risk for aerosolization, such as intubation or bronchoscopy, where use of an N95 respirator would be prudent."

Study limitations include the inability to determine compliance for all participants, that audits were conducted only on medical and pediatric units and not in the emergency department, the inability to account for the effect of indirect contact, and the inability to determine whether participants acquired influenza from hospital or community exposure.

"In routine health care settings, particularly where the availability of N95 respirators is limited, surgical masks appear to be non-inferior to N95 respirators for protecting health care workers against influenza," the study authors conclude.

In an accompanying editorial, Arjun Srinivasan, MD, from the Centers for Disease Control and Prevention in Atlanta, Georgia, and Trish M. Perl, MD, MSc, from the School of Medicine and Bloomberg School of Public Health at Johns Hopkins University in Baltimore, Maryland, note that appropriately designed and worn N95 respirators protect wearers from small-particle exposure.

For most patient care, the World Health Organization and the Society for Healthcare Epidemiology of America recommend the use of surgical masks, whereas the Centers for Disease Control and Prevention and the Institute of Medicine recommend wearing N95 respirators when caring for patients infected with H1N1 influenza.

"That this study is, to our knowledge, the first and only published randomized trial assessing respiratory protection for preventing influenza transmission is a sad commentary on the state of research in this area," Dr. Srinivasan and Dr. Perl write. "Uncovering the truth and identifying the most appropriate way to protect health care personnel will require that other investigators build on this study. Ultimately, accumulating a body of evidence on this topic will provide much-needed answers."

They also stress the importance of other measures to prevent influenza transmission, including vaccination and hand hygiene.

"While the debate over the role of respiratory protection in preventing influenza transmission will continue, neither the ongoing discussion nor the need for more research should excuse anyone from failing to implement other measures that are known to protect patients and HCP [healthcare personnel] from influenza," they conclude.

The Public Health Agency of Canada supported this study. The study authors and editorialists have disclosed no relevant financial relationships.

JAMA. Published online October 1, 2009. Study, Editorial

Clinical Context

Although many healthcare personnel are currently receiving their vaccinations against influenza, the current pandemic also highlights the importance of simple preventive measures to control the rate of influenza infection. A study by Grayson and colleagues, which was published in the February 1, 2009, issue of Clinical Infectious Disease, compared the efficacy of washing hands with soap and water vs alcohol-based gels among volunteers whose hands were purposefully contaminated with the influenza H1N1 virus. They found that both strategies were effective in reducing the amount of detectable virus on the hands, with soap and water associated with slightly superior results. However, without any hand hygiene protocol, viral concentrations on the hands remained generally high 60 minutes after inoculation.

Respiratory protection is another relatively easy means to prevent the spread of infection, but masks such as the N95 respirator can be expensive. The current study compares the N95 respirator vs simple surgical masks in the prevention of infection with influenza.

Study Highlights

• The study cohort consisted of nurses who worked in one of 8 tertiary hospitals in Ontario, Canada. The nurses worked in the emergency department, medicine, and pediatrics units.
• The provincial standards in Ontario dictate the use of respiratory protection when caring for patients with a febrile respiratory tract illness. Nurses also routinely wear gowns and gloves when caring for these patients.
• Nurses were randomly assigned to receive a fit-tested N95 respirator in these encounters or a surgical mask currently in use in their hospital.
• Nurses were required to report any influenza symptoms in twice-weekly questionnaires. Those with positive symptoms collected a flocked nasal specimen for viral polymerase chain reaction testing.
• The primary outcome of this study was the incidence of laboratory-confirmed influenza, which was defined by a positive result on a viral polymerase chain reaction test or at least a 4-fold increase in serum antibody titers to circulating influenza strain antigens. Blood samples for serologic testing were obtained before randomization and at the end of the trial period.
• Secondary outcomes included the incidence of other virus infections and influenza-like illness, which was defined by cough and fever. Researchers also followed the number of clinician visits for respiratory tract illness and work-related absenteeism.
• Each individual outcome was counted only once per participant.
• 446 nurses underwent randomization to surgical masks or N95 respirators. A total of 94% of participants were women, and the mean age was 36.2 years. Approximately 30% of participants had received the 2008 to 2009 trivalent inactivated vaccine, with similar percentages in each randomized group.
• Approximately one quarter of participants had a household exposure to influenza-like illness during follow-up. This percentage was similar in the N95 respirator group and the surgical mask group.
• Follow-up for study outcomes began in January 2009 and ended in April 2009, for a mean follow-up duration of 97 days in both groups. A total of 223 nasal specimens were collected during this interval.
• Adherence to wearing the mask was good in both groups.
• Laboratory-confirmed influenza occurred in 23.6% and 22.9% of the surgical mask group and N95 respirator group, respectively, a nonsignificant difference. The surgical mask was noninferior to the N95 respirator for all influenza infections as well as H1N1 infection specifically.
• Similarly, there was no difference between randomized groups in the rates of infection with respiratory syncytial virus type B, parainfluenza 3, rhinovirus-enterovirus, or coronoviruses.
• The gross rates of influenza-like illness were 4.2% and 1% in the surgical mask group and N95 respirator group, respectively. This result just missed statistical significance.
• Nearly 70% of individuals with influenza infection detected on serologic testing were asymptomatic.
• Rates of clinician visits for respiratory tract illness, work-related absenteeism, and lower respiratory tract infection were similar in comparing randomized groups.

Clinical Implications

• A previous study found that both hand washing with soap and water and alcohol-based gels were effective in reducing the amount of detectable influenza virus on the hands, with soap and water associated with slightly superior results. However, without any hand hygiene protocol, viral concentrations on the hands remained generally high 60 minutes after inoculation.
• The current study suggests that surgical masks are not inferior to N95 respirators in protecting healthcare personnel from infection with influenza.