Respiratory Precautions for Protection from Bioaerosols or Infectious Agents: A Review of the Clinical Effectiveness and Guidelines [Internet] - PubMed

Ottawa (ON): Canadian Agency for Drugs and Technologies in Health; 2014 Aug 19.

There are a number of infectious diseases that are transmitted from person to person via the respiratory route, including influenza, tuberculosis (TB), and severe acute respiratory syndrome (SARS) coronavirus, and these infectious agents are associated with considerable morbidity and mortality. Healthcare workers (HCWs) are vulnerable to exposure to these agents given the nature of their jobs, and as a result, risk both becoming infected, and spreading the infectious agents to other patients. To avoid transmission of these infectious diseases to (HCWs), exposure-appropriate respiratory precautions are sometimes necessary to protect both HCWs and the patients they care for. However, the selection of respiratory equipment depends on the pathogen, aerosol generation rate, and ventilation rate.

Two types of devices that are commonly used to prevent transmission of airborne infectious agents are medical masks and respirators. For this report, medical masks (also known as surgical masks or surgical face masks) are defined as unfitted devices worn by the healthcare worker (HCW) “to reduce transfer of potentially infectious bodily fluids between individuals”. Masks are designed prevent droplets from an infectious patient from coming in contact with the mucous membranes in the nose and mouth of the person wearing the mask. It must be noted that masks are not designed to filter small airborne infectious particles. In contrast, respirators are “medical devices designed to protect the wearer from airborne infectious aerosols transmitted directly from the patient or when artificially created such as during aerosol-generating procedures”, and this is done by filtering the airborne particles (known as an air-purifying respirator) or supplying clean air to the person wearing the respirator (known as an atmosphere-supplying respirator). Air-purifying respirators are further classified by the efficiency at which they remove particles (95%, 99%, and 100%), and into N-Series respirators that are not resistant to oil (N95, N99, N100), R-Series that are resistant to oil (R95, R99, R100), and P-Series that are oil-proof (P95, P99, P100).

As the Canadian Biosafety Standards and Guidelines note: “Using the wrong respirator or misusing one can be as dangerous as not using one at all”. Given the variety of devices, respirators, and potential infectious exposures, the purpose of this report is to identify studies and clinical practice guidelines examining the clinical effectiveness of exposure-appropriate respiratory protection for HCWs at risk of exposure to airborne infectious agents.