Personal respiratory protection against Mycobacterium tuberculosis.

Although there are no data demonstrating the effectiveness of personal respiratory protection in the prevention of occupational tuberculosis, there are sound theoretical bases supporting the use of respirators to reduce the risk of inhalational exposure. The major factor that limits the effectiveness of most respirators is the leakage between the face and the mask. There are data suggesting that traditional fit testing of respirators does not adequately predict the degree of protection in actual use, and more research is needed in that area. There is a large range of infectiousness of aerosols of TB, and classes of respirators vary greatly in the degree of protection they offer. I have argued that respirator selection should be based on anticipated exposures. High-risk exposures to TB are often associated with cough-inducing procedures or with aerosolization of infected tissues during autopsies. In my opinion, the most reasonable type of respirator for such high-risk situations in health care settings is a PAPR hood. The concentration of infectious aerosols in well-ventilated respiratory isolation rooms is likely to be very low, and the new N95 respirators offer a reasonable balance of comfort, cost, practicality, and protection. Preliminary data from mathematical modeling studies suggest there may be little additional benefit from more sophisticated personal respiratory protection in such settings. Additional research is needed to more accurately assess exposures to TB, to determine the size and aerodynamic behavior of TB generated by infectious patients, and to more accurately define the role and effectiveness of personal respiratory protection against TB.