TB Infection Control: Engineering (Environmental) Controls

1. 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

2. 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.

3. Key Points • Engineering controls (EC) are the 2nd 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

4. Fundamentals of Infection Control • 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

5. Administrative Controls Environmental Controls Respiratory Protection Hierarchy of Infection Control

6. Hierarchy of Infection Controls Administrative Environmental Respiratory protection Worker Patient Setting

7. 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

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

9. 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

12. Local exhaust ventilation • Source capture • Exterior hoods • Enclosing hoods Uganda

13. 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

15. Facility Airflow Direction • Clean to less clean • Negative pressure

16. Facility Airflow Direction • Clean to less clean • Negative pressure

17. Bronchoscopy Brazil

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

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

22. 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!

23. 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

27. Evaluation of Room Air Cleaners 1,000 Position 1 Position 2 100 Position 3 Position 4 Position 5 Colony Forming Units (CFUs) Position 6 Position 7 Position 8 10 Position 9 Linear Off On 1 0 2 4 6 8 10 Elapsed Time (hours)

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

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

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

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

34. 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

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

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

37. Risk of Close Exposure?

38. Infectious Case HCW

39. 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