4/17/2013. The Implementation of WHO Guidelines on Construction/ Engineering Aspect of TB Infection Control

Transcription

1 The Implementation of WHO Guidelines on Construction/ Engineering Aspect of TB Infection Control Setiawan Jati Laksono TUB Unit WHO Country Office Indonesia 1

2 WHO guidance TB Infection control 1999 Facility-level guidance 2003 Addendum Increased emphasis on HCW screening/safety 2006 Natural Ventilation 2009 Revision Increased managerial component 2

3 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 Health service units. Notes from Toman s Tuberculosis Questions and Answers (Second Edition 2004). Where is tuberculosis (most likely)spread and how can spread be reduced The Number of cases capable of transmitting M.tuberculosis in a community (principally smear-positive cases) The duration of infectiousness of such cases The number and duration of encounters between a source of infection and susceptible individuals Rieder H, 2004 Dynamics of Cough Large Droplets fall fast! Small droplets hang around slowly evaporate. crystallize creating a nucleus of infectious material inside 1.0 micron droplet nucleus will eventually fall just 3 m in 24 hrs! Large droplets upper airway trapping 1-5µ droplet nuclei reach alveoli & cause infection 3

4 Healthcare Facility Challenges Unsuspected (undiagnosed) cases visiting OPD s that have not been designed for triaging of suspected pulmonary disease Not all visitors to OPD s will be screened Patient flow paths in Hospitals (and clinics) due to department relationships. Unsuspected cases may be admitted for unrelated medical reasons. Reality (1) Departmental waiting areas. Health and safety compromised Administrative pressures drive No Triage procedures Reality (2) Administrative pressures drive Triage procedures No departmental waiting areas. Health and safety compromised 4

5 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 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 Infection control: Identifying high risk areas 5

6 Examples of high risk areas and procedures TB and M(X)DR-TB departments Waiting areas and diagnostic departments before diagnosis Holding areas for prisoners before transfer Sputum collection rooms Laboratory? Bronchoscopy? Surgery? Environmental Controls: Principles Control source of infection Dilute and remove contaminated air Control airflow Keep infectious air moving outside Keep HCWs upwind, infectious patients downwind Environmental Controls: Techniques Isolation / Spacing Ventilation Ultraviolet Germicidal Irradiation (UVGI) HEPA filtration 6

7 Isolation/ Spacing Others 7

8 Environmental Controls Isolation & Spacing Airborne isolation areas Individual rooms Well-spaced wards Min 6 ft. distance between 2 beds 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 8

9 Bronchoscopy Brazil 27 9

10 Ventilation 10

11 What is ventilation? Movement of air Pushing and/or pulling of particles and vapors Preferably in a controlled manner 31 Effective ventilation? Principles Air exchange >6 Air-exchanges per hour (ACH) in typical health care setting (60 l/s/pt) >12 ACH in high risk settings ( l/s/pt ) Corriders : 2.5 l/s/pt Control of flow Clean air in Contaminated air outside (away from patient care areas) Ventilation control Types of ventilation Natural Local General 33 11

12 Natural Ventilation Created by the use of external airflow generated by natural forces (wind, temperature differences) Can achieve very high ventilstion rste under ideal conditions Low cost and Maintenance free High ceiling and large windows on more than one wall Windows and doors should be opened in all season and also during night time Adequate and extra clothing is required in winter and rainy season Exhaust fans supplements the natural ventilation Natural Ventilation: Wind Natural Ventilation: Stack 12

13 Main WHO Recommendations for Natural Ventilation: 1. To help prevent airborne infections, adequate ventilation in health-care facilities in all patient-care areas is necessary. 2. For natural ventilation, the following minimum hourly averaged ventilation rates should be provided: 160 l/s/patient (hourly average ventilation rate) for airborne precaution rooms (with a minimum of 80 l/s/patient) (note that this only applies to new health-care facilities and major renovations); 60 l/s/patient for general wards and outpatient departments; and 2.5 l/s/m3 for corridors and other transient spaces without a fixed number of patients; however, when patient care is undertaken in corridors during emergency or other situations, the same ventilation rate requirements for airborne precaution rooms or general wards will apply. 3. When natural ventilation alone cannot satisfy the recommended ventilation requirements, alternative ventilation systems, such as hybrid (mixed-mode) natural ventilation should be considered, and then if that is not enough, mechanical ventilation should be used 4. When designing naturally ventilated health-care facilities, overall airflow should bring the air from the agent sources to areas where there is sufficient dilution, and preferably to the outdoors. 5. For spaces where aerosol-generating procedures associated with pathogen transmission are conducted, the natural ventilation requirement should, as a minimum, follow Recommendation 2. Should the agent be airborne, Recommendations 2 and 4 should be followed. Source capture Local exhaust ventilation Exterior hoods Enclosing hoods 13

14 Examples of General Ventilation Single pass First choice Recirculating HEPA filtration Room Air Mixing and Air Flow Prevent air stagnation Prevent short circuiting Air direction Air temperature Space configuration Movement 41 14

15 Exhaust fans in an open space do not improve ventilation or control airflow Natural ventilations works well, if allowed Escombe et al, PLOS Med 2007 Data from environmental study of 8 hospitals in Lima, Peru 15

16 TB WARDS TB CLINICS TB Clinic Alley Warehouse 16

17 - Escombe AR et al. Plos Med 2007 ; 4: e68 Efficient installation requires blocking the opening around the fan and sometimes it s better just to open the windows instead MDR TB Clinics 17

18 MDR TB Ward ACH : 52 All open 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! Dilution Ventilation 18

19 Window Window closed 4/17/2013 Dilution Ventilation Example: ACH calculation in a room 1 m 2 Bed 0.20 m/sec 1 m 2 Window 0.10 m/sec Window closed Room volume: 4.5 m x 4.m x 3.5 m= 63 m 3 Average Flow Rate= Average air velocity /2=0.15 m/sec x Area of window=2 m 2 x 3,600 sec = 0.15 x 2 x 3,600= =1,080 m3 / h ACH= Average Flowrate / Room Volume Bed Door ACH= 1,080 m 3 /h / 63 m 3 = Air changes per hour (ACH) and time required for removal efficiencies of 99% and 99.9% of airbone contaminants 19

20 Facility Airflow Direction Clean to less clean Negative pressure 200 m3/h 225 m3/h 135 m3/h 225 m3/h 200 m3/h CLEAN ZONE PASSAGE INFECTED ZONE Positive Pressure Neutral Pressure Negative Pressure 25 m3/h 25 m3/h Facility Airflow Direction Clean to less clean Negative pressure Limitations of Ventilation 20

21 Waiting area Examination rooms 4/17/2013 Problem: Plane View Front View(A) Waiting room at corridor X X X X Door opening office office office windows Side A drugs Doors in/ out Side view (B) Side B Solution Plane view Front view Office Office Waiting area Office Side B Side A Pharmacy Doors in/ out 3 Windows tranformed into doors Alternative waiting area maximizing natural ventilation in an out-patient clinic Side B Problems 21

22 Solution: Problem: HEPA/ FILTRATION 22

23 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 67 Design of Isolation room 23

24 UVGI 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 Exposure of M. tuberculosis droplet nuclei to a sufficient dose of UV radiation at 254 nanometers (nm) results in inactivation

25 Upper Air UVGI W/cm2 Kill zone Upper Air Beam UVGI 10 >100 W/cm2 Avoids reflectivity exposure, but may be less effective as less air irradiated 75 25

26 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 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 MATUR NUWUN AIC Policy TB Infection MEDICO VIVERE, MISERE VIVERE 26