CDC: N95 respirators for HCWs in flu pandemic
Anticipate shortages, prioritize supplies
N95 respirators are rarely used as an infection control barrier during seasonal influenza outbreaks, but the emergence of a global pandemic flu strain would change that thinking rapidly. In the event that avian influenza A (H5N1) mutates into an easily transmissible pandemic strain, the Centers for Disease Control and Prevention is recommending that health care workers treating suspect or known flu patients wear N-95 respirators as a "prudent" self-protection measure.1
Recently posted CDC guidance on the issue emphasizes that surgical mask and respirator use are components of an overall system of infection control practices to prevent the spread of a pandemic strain. The document emphasizes that additional precautions are advisable during a pandemic — beyond what is typically recommended during a seasonal influenza outbreak — in view of the lack of pre-existing immunity to a pandemic influenza strain, and the potential for the occurrence of severe disease and a high case-fatality rate. "Extra precautions might be especially prudent during the initial stages of a pandemic, when viral transmission and virulence characteristics are uncertain, and medical countermeasures, such as vaccine and antiviral, may not be available," the CDC states.
The CDC is recommending that during a pandemic, N-95 or higher rated respirators should be worn during medical procedures such as endotracheal intubation that have a high likelihood of generating infectious respiratory aerosols. Use of N-95 respirators also is prudent for health care personnel during other direct patient care activities (e.g., examination, bathing, feeding) and for support staff who may have direct contact with pandemic influenza patients, the CDC recommends.
"If N-95 or other types of respirators are not available, surgical masks provide benefit against large-droplet exposure and should be worn for all health care activities involving patients with confirmed or suspected pandemic influenza," the guidelines state. "Measures should be employed to minimize the number of personnel required to come in contact with suspected or confirmed pandemic influenza patients."
Since the publication of the HHS Pandemic Influenza Plan in November 2005, the U.S. Department of Health and Human Services (HHS) has faced an onslaught of comments and inquiries regarding infection control recommendations that relate to surgical mask and respirator use during an influenza pandemic. The CDC has been hampered by the lack of definitive data about the relative contributions and importance of such factors as: short-range inhalational exposure, large droplet mucosal exposure, and direct inoculation via hands or inanimate objects contaminated with virus (i.e., fomites) on influenza transmission.
"There is only limited information on optimal interventions to prevent influenza transmission and the effectiveness of interventions on an individual basis," the CDC guidelines state. "The lack of scientific consensus has led to conflicting recommendations by public health partners. Moreover, a large amount of incorrect, incomplete, and confusing information about surgical mask and respirator use has been disseminated on the Internet and by other popular media."
The CDC has reviewed the available data and combined the traditional infection control and industrial hygiene approaches to create a "science-based framework" to facilitate planning for surgical mask and respirator use in health care settings.
Droplet and airborne transmission
On the basis of epidemiologic patterns of disease transmission, large droplet transmission — via coughing and sneezing — has traditionally been considered a major route of seasonal influenza transmission. Transmission via large-particle droplets requires close contact between source and recipient persons because these larger droplets do not remain suspended in the air and generally travel only short distances. Three feet has often been used by infection control professionals as a guide for "short distance" and is based on studies of respiratory infections; however, for practical purposes, this distance may range from 3 to 6 feet. Special air handling and ventilation are not required to prevent droplet transmission, the recommendations stated.
While some observational studies and animal studies raise the possibility of short-range airborne transmission through small-particle aerosols, convincing evidence of airborne transmission of influenza viruses from person to person over long distances (e.g., through air-handling systems, or beyond a single room) has not been demonstrated, the CDC reported. Some organisms (e.g., Mycobacterium tuberculosis, measles virus, and varicella virus) can remain infectious while dispersed over long distances by air currents, causing infection in susceptible individuals who have not had face-to-face contact or been in the same room with the infectious individual. Special air handling and ventilation systems (e.g., negative-pressure rooms) are used in health care settings to assist in preventing spread of agents that may be dispersed over long distances. In contrast to those agents, the pattern of disease spread for seasonal influenza does not suggest transmission across long distances through ventilation systems. Therefore, negative-pressure rooms are not needed for patients with seasonal influenza, the CDC stated. However, localized airborne transmission may occur over short distances (i.e., 3 to 6 feet) via droplet nuclei or particles that are small enough to be inhaled. The relative contribution of short-range airborne transmission to influenza outbreaks is unknown.
It also is likely that some aerosol-generating medical procedures (e.g., endotracheal intubation, open suctioning, nebulizer treatment, bronchoscopy) could increase the potential for generation of small aerosols in the immediate vicinity of the patient. Although this mode of transmission has not been evaluated for influenza, given what is known about these procedures, additional precautions for health care personnel who perform aerosol-generating procedures on influenza patients are warranted.
CDC recommendations for respirator and mask use in health care settings in the event of an influenza pandemic include the following measures:
1. National Institute for Occupational Safety and Health (NIOSH)-certified respirators (N-95 or higher) are recommended for use during activities that have a high likelihood of generating infectious respiratory aerosols, including the following high-risk situations:
• Aerosol-generating procedures (e.g., endotracheal intubation, nebulizer treatment, and bronchoscopy) performed on patients with confirmed or suspected pandemic influenza;
• Resuscitation of a patient with confirmed or suspected pandemic influenza (i.e., emergency intubation or cardiac pulmonary resuscitation);
• Providing direct care for patients with confirmed or suspected pandemic influenza-associated pneumonia (as determined on the basis of clinical diagnosis or chest X-ray), who might produce larger-than-normal amounts of respirable infectious particles when they cough.
In the event of actual or anticipated shortages of N-95 respirators:
• Other NIOSH-certified N-, R-, or P-class respirators should be considered in lieu of the N-95 respirator.
• If reusable elastomeric respirators are used, these respirators must be decontaminated according to the manufacturer's instructions after each use.
• Powered air purifying respirators (PAPRs) may be considered for certain workers and tasks (e.g., high-risk activities). Loose-fitting PAPRs have the advantages of providing eye protection, being comfortable to wear, and not requiring fit-testing; however, hearing (e.g., for auscultation) is impaired, limiting their utility for clinical care. Training is required to ensure proper use and care of PAPRs.
2. Use of N-95 respirators for other direct care activities involving patients with confirmed or suspected pandemic influenza also is prudent. Hospital planners should take this into consideration during planning and preparation in their facilities when ordering supplies. In addition, several measures can be employed to minimize the number of personnel required to come in contact with suspected or confirmed pandemic influenza patients, thereby reducing worker exposure and minimizing the demand for respirators. Such measures include the following:
• Establishing specific wards for patients with pandemic influenza;
• Assigning dedicated staff (e.g., health care, housekeeping, janitorial) to provide care for pandemic influenza patients and restricting those staff from working with noninfluenza patients;
• Dedicating entrances and passageways for influenza patients.
Planning assumptions and projections suggest that shortages of respirators are likely in a sustained pandemic. Therefore, in the event of an actual or anticipated shortage, hospital planners must ensure that sufficient numbers of respirators are prioritized for use during the high-risk procedures described in Recommendation One. This will require careful planning as well as real-time supply monitoring to ensure that excess respirators are not held in reserve while health care personnel are conducting activities for which they would otherwise be provided respiratory protection.
Avoid excessive use
Conversely, excessive use of respirators could result in their unavailability for high-risk procedures. Decision guidance for determining respirator wear should consider factors such as duration, frequency, proximity, and degree of contact with the patient. Occupational health and safety professionals can assist with making these site- and activity-specific decisions. For example, a nurse entering a room with a suspected or confirmed pandemic influenza patient to obtain vital signs should wear an N-95 respirator. A housekeeper entering multiple rooms of confirmed or suspected influenza patients to mop floors or clean patient equipment should be similarly protected. Work activities such as those performed by a receptionist at the entrance of a hospital should be designed to prevent exposure of the worker to large numbers of potentially infected patients. In such situations, the use of transparent barriers or enclosures is preferable to the use of respirators.
If supplies of N-95 (or higher) respirators are not available, surgical masks can provide benefits against large droplet exposure, and should be worn for all health care activities for patients with confirmed or suspected pandemic-influenza.
3. Negative-pressure isolation is not required for routine patient care of individuals with pandemic influenza. If possible, airborne infection isolation rooms should be used when performing high-risk aerosol-generating procedures. If work flow, timing, resources, availability, or other factors prevent the use of airborne infection isolation rooms, it is prudent to conduct these activities in a private room (with the door closed) or other enclosed area, if possible, and to limit personnel in the room to the minimum number necessary to perform the procedure properly.
Reference
- Centers for Disease Control and Prevention. Interim Guidance on Planning for the Use of Surgical Masks and Respirators in Health Care Settings during an Influenza Pandemic. Available at: www.pandemicflu.gov/plan/maskguidancehc.html.
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