Isolation rooms for tuberculosis control.

A survey of respiratory isolation rooms in seven St. Louis hospitals reported in this month’s issue. begins to verify a general suspicion that many hospitals lack adequate facilities for treating patients with airborne infectious diseases such as tuberculosis (TB). Respiratory isolation rooms should be under continual “negative pressure” relative to hallways and anterooms, so that air flows from the more travelled areas into the isolation rooms, even when connecting doors are opened. To highlight their findings, Fraser et al’ reported that 45% of designated respiratory isolation rooms in their study failed this test. Although a larger number of isolation rooms in newer hospitals had anterooms, even these did not ensure the desired direction of airflow. None of the hospitals had a regular program to evaluate the airflow rates and pressure differences for their isolation facilities. These findings complement other recent surveys on the adequacy of respiratory isolation rooms. In 1992, the Centers for Disease Control and Prevention (CDC) and the American Hospital Association surveyed a statistical sample of U.S. hospitals to evaluate the status of their TB control measures and to identify areas needing improvement. Preliminary results indicated that 27% of the hospitals lacked isolation rooms meeting minimum CDC recommendations.3 It is likely that if the rooms in the presumably complying hospitals were tested, a number would be found deficient. In the commentary below, we offer our thoughts on designing and testing respiratory isolation rooms. We also address several issues specifically related to TB control: estimating the number of isolation rooms needed, protecting high-risk healthcare workers, the physical science underlying airborne infection control, and principles of infection risk assessment and risk management.