Difference between revisions of "Guidelines for safe sputum collection"

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===Local exhaust ventilation devices===
 
===Local exhaust ventilation devices===
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Local exhaust ventilation devices capture of airborne contaminants at or near the source before they are dispersed into the work space <ref name=":0">Burgess, W.A., Ellenbecker, M.J., and Treitman, R.D. 2004. Ventilation for control of the work environment. Second edition. New Jersey USA. John Wiley & Sons</ref><ref name=":1">Heinsohn, P. 1996. Tuberculosis resources guide CEC Report CR 106146. Carlifonia. USA. Heinsohn Consulting services.</ref>. The basic components of an LEV device are hood, ductwork, air cleaner and fan <ref name=":1" />. Burgess, et al.,<ref name=":0" /> identifies two major categories of LEV devices; enclosures and exterior. The major difference between these two is that for enclosures, contaminants are released from inside the device whereas for exterior contaminants are released outside the device. A sputum booth is considered as an example of an enclosure LEV device. Illustrations of an enclosure and exterior LEV devices are shown in Figures 1 and 2 respectively. Figure 1 shows a CSIR designed sputum booth. [[Technical specifications for CSIR designed sputum booth|Technical specifications for CSIR designed sputum booth.]]
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Local exhaust ventilation devices capture of airborne contaminants at or near the source before they are dispersed into the work space <ref name=":0">Burgess, W.A., Ellenbecker, M.J., and Treitman, R.D. 2004. Ventilation for control of the work environment. Second edition. New Jersey USA. John Wiley & Sons</ref><ref name=":1">Heinsohn, P. 1996. Tuberculosis resources guide CEC Report CR 106146. Carlifonia. USA. Heinsohn Consulting services.</ref>. The basic components of an LEV device are hood, ductwork, air cleaner and fan <ref name=":1" />. Burgess, et al.,<ref name=":0" /> identifies two major categories of LEV devices; enclosures and exterior. The major difference between these two is that for enclosures, contaminants are released from inside the device whereas for exterior contaminants are released outside the device. A sputum booth is considered as an example of an enclosure LEV device. Illustrations of an enclosure and exterior LEV devices are shown below as Mechanical sputum booth. The Mechanical sputum booth was designed by the Infrastructure Innovation unit of the CSIR . [[Technical specifications for CSIR designed sputum booth|Technical specifications for CSIR designed sputum booth.]]
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[[File:Mechanical sputum booth.jpg|none|thumb|Mechanical sputum booth]]Table 1 gives a comparison between enclosure and exterior LEV devices.<br />
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[[File:Mechanical sputum booth.jpg|none|thumb|Mechanical sputum booth]]Comparison between enclosure and exterior LEV devices is shown in Table below.<br />
  
  
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Table 1. Comparison between enclosure and exterior LEV devices
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Comparison between enclosure and exterior LEV devices
 
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|'''Local Exhaust Ventilation  device'''
 
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|'''''Enclosure'''''
 
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Contaminants  are released from inside the LEV device. Example is a booth as illustrated in  Figure 1.
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Contaminants  are released from inside the LEV device. Example Mechanical sputum booth is shown above.
 
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*Complete physical separation  between patient and staff which ensures negligible exposure to contaminants  hence providing the greatest protection when compared to exterior <ref name=":0" />.
 
*Complete physical separation  between patient and staff which ensures negligible exposure to contaminants  hence providing the greatest protection when compared to exterior <ref name=":0" />.
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|'''''Exterior'''''
 
|'''''Exterior'''''
  
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Contaminants  are released from outside the LEV device. Example is illustrated in Figure 2.
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Contaminants  are released from outside the LEV device. Example exterior LEV is illustrated above.<br />
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*Cost is relatively low compared  to complete enclosures.
 
*Cost is relatively low compared  to complete enclosures.

Revision as of 09:01, 19 October 2020

Introduction

Sputum specimen examination is the main diagnostic procedure for pulmonary Tuberculosis [1]; however, the medical procedure (patient coughing) that is used for sputum collection increases the potential for transmission of M. Tuberculosis significantly [2]; therefore, there is need to administer sputum collection safely in healthcare facilities [3]. The CSIR’s Infrastructure Innovation research group has conducted many TB risk assessments in South African public healthcare facilities for over 10 years. A common finding was that engineering controls for sputum collection were not always adequate, maintained or monitored. Sputum was observed to be collected from toilets, consulting rooms and counselling rooms which implies increased risk of TB transmission. This guideline provide guidance on conducting sputum collection safely for suspected or known infectious TB patients. Although there is a three level hierarchy of control measures; administrative controls, engineering controls and personal respiratory protection to prevent transmission of TB, this guideline is limited to engineering control measures for sputum collection.

Engineering control measures for sputum collection

There are two main types of engineering methodologies that can be utilized for sputum collection; local exhaust ventilation devices and sputum collection/induction rooms.

Local exhaust ventilation devices

Local exhaust ventilation devices capture of airborne contaminants at or near the source before they are dispersed into the work space [4][5]. The basic components of an LEV device are hood, ductwork, air cleaner and fan [5]. Burgess, et al.,[4] identifies two major categories of LEV devices; enclosures and exterior. The major difference between these two is that for enclosures, contaminants are released from inside the device whereas for exterior contaminants are released outside the device. A sputum booth is considered as an example of an enclosure LEV device. Illustrations of an enclosure and exterior LEV devices are shown below as Mechanical sputum booth. The Mechanical sputum booth was designed by the Infrastructure Innovation unit of the CSIR . Technical specifications for CSIR designed sputum booth.

Mechanical sputum booth

Comparison between enclosure and exterior LEV devices is shown in Table below.


Comparison between enclosure and exterior LEV devices

Local Exhaust Ventilation device Advantages Disadvantages
Enclosure

Contaminants are released from inside the LEV device. Example Mechanical sputum booth is shown above.

  • Complete physical separation between patient and staff which ensures negligible exposure to contaminants hence providing the greatest protection when compared to exterior [4].
  • Conserves energy when compared to the external LEV since it requires least amount of airflow to ensure adequate control [4].
  • An exhaust airflow is chosen sufficient to create a negative air pressure inside the LEV; this ensures that contaminated air will not escape from the device [4].
  • Contaminants are quickly captured due to high air change rates. Therefore shorter contaminants clearance times when compared to sputum collection rooms.
  • Devices with HEPA-filtered exhaust can be used in any room.
  • Can be moved to accommodate room function changes.
  • Cost is higher than external LEV device approximately R125 000.
  • Requires routine maintenance such as changing the HEPA filter and pre-filter.
  • Booths are not as portable as exterior LEV device.
Exterior

Contaminants are released from outside the LEV device. Example exterior LEV is illustrated above.
  • Cost is relatively low compared to complete enclosures.
  • Portable, small enough to be used at patient’s bedside.
  • Exterior LEV devices are susceptible to cross-drafts which may completely disrupt their performance by disrupting the airflow patterns between the point of contaminant release and the exhaust [4].
  • Since the contaminants are released into the air surrounding an exterior LEV device and then captured, it is possible for a healthcare worker to be in the path between the contaminant source and the device, and be exposed to the contaminants before they are captured [4].
  • Does not provide complete physical separation between patient and staff.
  • Requires more supervision of patient to ensure proper placement than complete enclosures.
  • Open windows or doors, or people moving in the area can create drafts, which disrupt the capture of airborne particles.

Sputum collection room

This room should meet the following requirements:

  • It should be mechanically ventilated.
  • It should be designed with negative air pressure with respect to adjacent spaces so that air flows from adjacent spaces into the room.
  • The ventilation rate of the room should be at least 12 ACH.


Engineering control measure Advantages Disadvantages
Sputum Induction Rooms

The room should meet all the requirements stated in section 2.2.

  • Provides complete separation between staff and patients
  • If a negative pressure isolation room is available, sputum induction can be done in this room with no additional ventilation equipment.
  • Separate designated room required
  • If a negative pressure isolation room is not available, these rooms require installation of dedicated exhaust systems or HEPA filtration systems prior to recirculation of air.
  • Airborne particle clearance times will be high due to lower ACH rates when compared to enclosure LEV devices.
  • Room ventilation system must be monitored to ensure proper operation
  • Most expensive option if an existing negative pressure isolation room is not available

Testing of LEV devices and sputum collection room

Testing and monitoring of the LEV devices and sputum collection rooms is done to ensure correct continued operation of the systems.

Test Engineering control Recommended frequency of testing Test method Apparatus Perfomance specification guideline/ standard
Air pressure difference Sputum induction room, Enclosure LEV Daily inspection 2.4.1 Electronic micromanometer, mechanical differential pressure gauge (magnehelic gauge) Greater than -2.5Pa[6].
Total air flow rate measurement Sputum induction room, Enclosure LEV Once every 6 months 2.4.2 Flowhood with flowmeter or a combination of flowhood and anemometer (thermal or vane) Greater than or equal to 12 ACH for sputum induction room[6].
Airflow direction and visualisation Sputum induction room, Enclosure LEV Daily inspection 2.4.3 Silk thread, Smoke Tubes, nicotine free electronic cigarettes. Air should flow into the room and into LEV[6]
Installed HEPA filter system leakage Enclosure LEV Once every 6 months 2.4.4 Aerosol generator as per ISO 14644:3 section C.6.3 and aerosol photometer Filter penetration should not exceed 0,05% as per EN1822 standard.

Test Methods

Air pressure difference test

The test is perfomed to verify the capability of the enclosure LEV and sputum induction room to maintain the specified pressure difference with respect to adjacent spaces. The test should be done with all doors closed. Permanent measuring points should be installed.

Total air flow rate measurement

Measurement of total airflow rate is carried out to calculate the clean air volume supplied to the Sputum induction room and Enclosure LEV per unit time, and this value can be used to calculate the air changes per unit time and airborne particle clearance times.

Airflow direction and visualisation

The purpose of airflow direction tests and visualisation is to confirm that the airflow direction conform to the design and performance specification and also to test for stagnant zones of sputum induction room and Enclosure LEV.

Installed HEPA filter system leakage

The test is perfomed to confirm that the HEPA filter is properly installed by verifying the absence of bypass leakage in the installation and that the filter is free of defects (small holes and damages in the filter medium and frame seal). The test is perfomed by introducing a 0.5µm to 0.7µm (as per ISO 14644:3 section B.6.2.2) aerosol upstream and scanning downstream of the filter.


Maintenance of LEV devices and sputum collection room

The required maintenance activities, interval, responsible person are detailed in Table 3.

Maintenance activity Engineering control Time interval Responsible person
Visual inspection of pressure gauges for HEPA and pre-filters Enclosure and exterior LEV and sputum room Daily Facility maintenance personnel
Check fan failure Enclosure and exterior LEV and sputum room Weekly Facility maintenance personnel
Replace fan Enclosure and exterior LEV and sputum room As needed according to manufacturer's maintenance manual Qualified engineering specialist
Replace HEPA filter Enclosure and exterior LEV and sputum room When HEPA filter pressure gauge above 500Pa Qualified engineering specialist
Replace pre filter Enclosure and exterior LEV and sputum room When filter pressure gauge is above 250Pa Qualified engineering specialist
Replace pressure gauges Enclosure and exterior LEV and sputum room As needed according to manufacture's maintenance manual Qualified engineering specialist

Outdoor sputum collection site

The outdoor naturally sputum collection site should be located away from people and open doors. The TB services guideline[3] recommends a distance of at least 4m away from the buildings. An example outdoor sputum collection site is shown in Appendix B.

Factors to consider when procuring sputum booth

This guideline proposes an initial sputum collection risk assessment to be conducted before procuring a new sputum collection facility. The decision chart below can be used to establish the necessity for the procurement of a sputum collection facility and for the procurement of an appropriate sputum collection device.

Process to follow when procuring sputum collection facility













References

  1. ↑ Hansen, D. J., 1993. The Work Environment: Healthcare, Laboratories and Biosafety, Volume 2. Lewis publishers: USA.
  2. ↑ Centers for Disease Control and Prevention. Guidelines for Preventing the Transmission of Mycobacterium tuberculosis in Health-Care Settings, 2005. MMWR 2005;54(No. RR-17).
  3. ↑ 3.0 3.1 Infrastructure Unit Support Systems (IUSS), 2014. IUSS HEALTH FACILITY GUIDES: TB Services. South Africa. National Department of Health.
  4. ↑ 4.0 4.1 4.2 4.3 4.4 4.5 4.6 Burgess, W.A., Ellenbecker, M.J., and Treitman, R.D. 2004. Ventilation for control of the work environment. Second edition. New Jersey USA. John Wiley & Sons
  5. ↑ 5.0 5.1 Heinsohn, P. 1996. Tuberculosis resources guide CEC Report CR 106146. Carlifonia. USA. Heinsohn Consulting services.
  6. ↑ 6.0 6.1 6.2 Sehulster LM, Chinn RYW, Arduino MJ, Carpenter J, Donlan R, Ashford D, Besser R, Fields B, McNeil MM, Whitney C, Wong S, Juranek D, Cleveland J. Guidelines for environmental infection control in health-care facilities. Recommendations from CDC and the Healthcare Infection Control Practices Advisory Committee (HICPAC). Chicago IL; American Society for Healthcare Engineering/American Hospital Association; 2004.
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