TB Infection Control: Engineering (Environmental) Controls Kevin P. Fennelly, MD, MPH Division of Pulmonary & Critical Care Medicine Center for Emerging Pathogens UMDNJ-New Jersey Medical School

Objectives To review fundamental principles and practices of TB infection control related to engineering controls To discuss advantages and limitations to different engineering control measures. To discuss how engineering controls are used in the total TB Infection Control Plan. To discuss issues and questions specific to your experiences in Chiapas.

Key Points Engineering controls (EC) are the 2 nd priority in control measures AFTER administrative controls, But they are complementary Dilution ventilation is the most important EC – Protects HCWs, other patients, visitors – Has limits defined by technology, expense, comfort Negative pressure or directional airfllow keeps contaminated air away from HCWs UVGI and filtration devices are adjuncts or back- ups for high-risk areas – Require maintenance – Need to consider cost-effectiveness

Administrative controls: reduce risk of exposure Environmental controls: prevent spread and reduce concentration of droplet nuclei Respiratory protection controls: further reduce risk of exposure to wearer only Fundamentals of Infection Control

Hierarchy of Infection Control Respiratory Protection Administrative Controls Environmental Controls

Hierarchy of Infection Controls AdministrativeEnvironmentalRespiratoryprotection WorkerPatientSetting

TB-Infection Controls: Simplified Administrative: WHO? – Who is a TB suspect? – Who is at risk from exposure? – Who has infectious TB? – Who has drug resistant TB? Environmental: WHERE? – Where is optimal place to minimize risk? Personal Respiratory Protection: Special high risk settings

Environmental Controls Control source of infection Dilute and remove contaminated air Control airflow – Keep infectious air moving outside – Keep HCWs ‘upwind’, infectious patients ‘downwind’

Airborne Infection Isolation Room Policies Environmental factors and entry of visitors and HCWs should be controlled Air changes per hour (ACH) (volume /time) – >6 ACH (existing) – >12 ACH (new) Minimum of 2 ACH of outdoor air HCWs should wear at least N95 respirators

10 What is ventilation? Movement of air “Pushing” and/or “pulling” of particles and vapors Preferably in a controlled manner

11 Ventilation control Types of ventilation – Natural – Local – General

Local exhaust ventilation Source capture – Exterior hoods – Enclosing hoods Uganda

Examples of General Ventilation Single pass –First choice Recirculating –HEPA filtration

14 Room Air Mixing and Air Flow Prevent air stagnation Prevent short circuiting Air direction Air temperature Space configuration Movement

Clean to less clean Negative pressure Facility Airflow Direction

Clean to less clean Negative pressure Facility Airflow Direction

17 Bronchoscopy Brazil

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- Escombe AR et al. Plos Med 2007 ; 4: e68

Natural vs Mechanical Ventilation Good natural ventilation is better than bad mechanical ventilation. Major limitation of natural ventilation is that it depends upon outdoor weather conditions. Can control odor and improve comfort of occupants, but not if very cold or very hot. Usually we do not have a choice and must work with where we are!

Limitations of Ventilation

24 HEPA filtration Must be used – When discharging air from local exhaust ventilation booths or enclosures directly into the surrounding room, and – When discharging air from an AII room into the general ventilation system

25 Room Air Cleaners

26 TB Outpatient unit – Helio Fraga Institute, MoH, Rio de Janeiro

, Elapsed Time (hours) Colony Forming Units (CFUs) Position 1 Position 2 Position 3 Position 4 Position 5 Position 6 Position 7 Position 8 Position 9 Linear OffOn Evaluation of Room Air Cleaners

28 Ultraviolet Germicidal Irradition (UVGI) Used as supplement or back-up to dilution ventilation Does NOT provide negative pressure Requires maintenance, esp. cleaning bulbs Not effective at high humidity (>70%) Occupational exposure limits: eye & skin

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Xu P et al. Atmospheric Environment 2003; 37:405

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- Escombe AR et al. Plos Med 2009 (March) ; 6

Escombe AR et al. Plos Med 2009 (March) ; 6

Environmental Controls: Which one and When? Dilution ventilation, UVGI, and HEPA filter units are all effective under IDEAL laboratory conditions Best data in field support dilution ventilation Advantage of ventilation is usually ‘always on’, minimizing human errors. Disadvantages of UVGI and HEPAs – Maintenance (increased human errors) – Large variability of effectiveness – May cause false sense of reassurance

Assumptions: Homogenous distribution of infectious aerosol over 10 hours; uniform susceptibility. - Fennelly KP & Nardell EA. Infect Control Hosp Epidemiol 1998; 19;754 Control Measures are Synergistic & Complementary

Wells-Riley Equation: Mathematical model of airborne infection Pr{infection}=C/S=1-e (-Iqpt/Q) Where C=# S infectedx S=# susceptibles exposedx I = # infectors (# active pulm TB cases)x q = # infectious units produced/hr/Infectorx p = pulm ventilation rate/hr/S t = hours of exposurex Q = room ventilation rate with fresh air x Admin E.C.

Risk of Close Exposure?

HCW Infectious Case

Summary – TBIC Engineering Controls First priority is ADMINISTRATIVE controls, but EC are complementary Dilution ventilation is most important for all – Can add to comfort – But limited by technology, comfort, expense Negative pressure or directional airflow can keep infected air away (even if diluted) from HCWs UVGI and filtration devices are adjuncts for high risk areas – Back-up when not possible to ventilate well