TB Infection Control

Dear Gobe, do you have a UV meter? I thought that's the way to test it, or
did I just assume it?

As you all are aware I have reservations about the use of very expensive UV systems in the absence of other more proven interventions. It must be said that in small contained areas such as laboratory cabinets and barber's equipment decontamination is possible. In an open and dynamic air movement healthcare facility without control of ventilation, I am not so sure. I also find there is a lack of evidence regarding the efficacy in the presence of dust and non maintenance. I must put my cards on the table and say as an IPC clinician, I would rather, and do, spend my limited budget elsewhere.
Shaheen

Dear Prof. Mehtar, and colleagues,

In this instance I believe we are (almost) in complete agreement. One
must be very careful, however, to distinguish exactly how germicidal UV
is used. That is, to distinguish between:

1) DIRECT UV FOR SURFACE DECONTAMINATION as used for barber implements,
in some biological safety cabinets, for room surface decontamination in
Russia and other Eastern European countries, and for orthopedic
operating rooms in the US and Sweden (perhaps elsewhere). UV may NOT be
highly effective for surfaces because any micro-shadows can shield
organisms from UV. Imagine trying to decontaminate a barber's brush,
comb, or the intricacies of a room where the only organisms killed are
those in direct line with the rays and not shielded by dust, hair, or
other grime since germicidal (254 nm) UV does not penetrate surfaces
well. Generally, I would not recommend this use of UV, although there is
strong evidence supporting the reduction of orthopedic post-op
infections when properly used for that application. Room occupants
cannot be exposed to direct UV without fully protective clothing.

2) UV IN FAN-DRIVEN BOXES as is being discussed by Dr. Jensen and the
questioner from Botswana. Apart from the details Paul raises for ...

Dear Prof. Mehtar, and colleagues,

In this instance I believe we are (almost) in complete agreement. One
must be very careful, however, to distinguish exactly how germicidal UV
is used. That is, to distinguish between:

1) DIRECT UV FOR SURFACE DECONTAMINATION as used for barber implements,
in some biological safety cabinets, for room surface decontamination in
Russia and other Eastern European countries, and for orthopedic
operating rooms in the US and Sweden (perhaps elsewhere). UV may NOT be
highly effective for surfaces because any micro-shadows can shield
organisms from UV. Imagine trying to decontaminate a barber's brush,
comb, or the intricacies of a room where the only organisms killed are
those in direct line with the rays and not shielded by dust, hair, or
other grime since germicidal (254 nm) UV does not penetrate surfaces
well. Generally, I would not recommend this use of UV, although there is
strong evidence supporting the reduction of orthopedic post-op
infections when properly used for that application. Room occupants
cannot be exposed to direct UV without fully protective clothing.

2) UV IN FAN-DRIVEN BOXES as is being discussed by Dr. Jensen and the
questioner from Botswana. Apart from the details Paul raises for these
particular units (which are the ones we examined closely) there is a
general principle here. Yes, with enough UV intensity and contact time
(that is, UV dose), almost any viable microbe can be effectively killed
by such units. The fundamental problem is the clean air delivery rate
(CDR) and the size of the room. Putting the CDR together with the room
volume, you can calculate the "equivalent" room air changes per hour
(EqACH)". In the hospital in question in Botswana we calculated that a
single unit over the head of the bed was unlikely to add even 1 EqACH,
where as at least 6-12 ACH are desired. Moreover, that would assume
good air mixing. More likely, small units with low velocity air flow and
intake and exhaust close to one another are likely to recirculate the
air in the immediate vicinity of the unit, leaving the rest of the room
contaminated. Generally, except in small unventilated rooms or booths,
these units are not likely to be effective. All of Paul's other concerns
(do they really have UV, how easy to maintain) are also critical.

3) UPPER ROOM UV. Here we use UV lamps in fixtures that irradiate air in
the upper room while protecting occupants in the lower room from UV
exposure. The ideas is to use the entire upper room as an air
disinfection chamber, depending on air mixing between the lower occupied
room and the upper room to disinfect the air breathed in the lower room.
A slow paddle fan can greatly assist and assure air mixing. In test
rooms this approach has consistently been shown to produce 10 to 20
EqACH against TB organisms (BCG is similar to Mtb in UV susceptibility
as is used for these tests). However, the UV fixtures need to be
properly designed, properly installed, and properly maintained.
Maintenance can be as simple as turning them off and wiping down the
lamp (bulb) with alcohol once a month or once a week, depending on how
dusty the environment is. I agree with Dr. Mehtar that we see lots of
applications where the fixture designs, fixture room distribution,
and/or maintenance are not well done and the installations may not be
effective, or as effective as they could be.

The need for proper application and maintenance of any technology,
including natural ventilation, mechanical ventilation, administrative
controls, and use of respirators is the same. Natural ventilation does
not work as planned when the windows are closed, when the wind changes
direction, etc. There are no simple fixes and we must focus on the
details and train ourselves and our staff to apply these IC solutions
properly. That is precisely the purpose of this and other efforts.
However, we should not dismiss any potentially useful technology without
asking whether it is fundamentally flawed or could work well in your own
setting with proper attention to detail. The problem of the transmission
of TB, especially MDR and XDR TB is too great around the world not to
examine these issues in depth. This is my excuse for too long a response
to this discussion!!

Ed

Dear Ed
I bow to your vast expertise in this field, and I am delighted to see that sense prevails. Thank you for the wonderful explanation- it is really important that those living in low resource countries do not get duped by all sorts of UV light sales merchants. I have even seen a UV light box for hand decontamination!!
Thank you so much for clarifying this matter and I agree, we should tread carefully.
Best Regards
Shaheen

Dear Gobe,

Please note Paul's note to this discussion: https://www.ghdonline.org/ic/discussion/re-tb-infection-control-re-bulk-re-tb-infection-co/ and below.

Dear Gobe:

Thanks for posting this and welcome!!!

I will not be able to access the internet until this evening; however, I believe these are the same room air cleaners (with UV inside) that Ed and I saw at PMH MDR/XDR TB Department. Am I correct? If this is true, then all I can say at this time is that if the units are 100% effective (which has not been verified) in inactivating airborne MTB, you will need at least four of these units in each of the single-patient wards in the MDR/XDR department to obtain the equivalent of six air changes per hour of ventilation. The general medical wards are rather large areas and you will need many, many units! There are also two other disadvantages with these units. They do not provide any negative pressure nor do they provide directional airflow in the ward. I also have two other concerns. The unit we saw required us to remove it from the wall to access the back of the unit where the "screws" were located. Also, these screws ...

Dear Gobe,

Please note Paul's note to this discussion: https://www.ghdonline.org/ic/discussion/re-tb-infection-control-re-bulk-re-tb-infection-co/ and below.

Dear Gobe:

Thanks for posting this and welcome!!!

I will not be able to access the internet until this evening; however, I believe these are the same room air cleaners (with UV inside) that Ed and I saw at PMH MDR/XDR TB Department. Am I correct? If this is true, then all I can say at this time is that if the units are 100% effective (which has not been verified) in inactivating airborne MTB, you will need at least four of these units in each of the single-patient wards in the MDR/XDR department to obtain the equivalent of six air changes per hour of ventilation. The general medical wards are rather large areas and you will need many, many units! There are also two other disadvantages with these units. They do not provide any negative pressure nor do they provide directional airflow in the ward. I also have two other concerns. The unit we saw required us to remove it from the wall to access the back of the unit where the "screws" were located. Also, these screws has special "heads,"requiring a special tool. We were unable to open one up to see the inner workings; this will also mean that maintenance will not be simple! Finally, I had no measurable levels of UVGI after removing the filters by the fans; however, I could see blue light. We need to verify that these are UVGI (i.e., germicidal wavelength, 254 nm) lamps. Also, like upper-room (shielded) UVGI, these units require good air mixing to. Maximize their overall efficiency in the ward.

I will add more tonight.

Regards,

Paul J

Dear Paul
Thank you for that e-mail. It was most informative and helpful.
Regards
Shaheen

Gobe: We met in Boston at Harvard School of Public Health Coarse . I am a professional engineer providing services in HVAC and I am a partner in an air purification products company (L2B Environmental Systems Inc.).

In order to determine the overall efficiency of any UVGI appliance in your TB wards we would need the following data about your wards. The area of the proposed space, the volume of air delivered to the space from install HVAC equipment and placement of diffusers, whether the air delivered is recirculated or 100% fresh make-up air, the natural air exchange rate of the space or if window and doors are open and the ceiling height. To size the appliance and to determine the number of appliances required in the space the engineering specifications of the appliance is required. The air delivery rate of the appliance and the UVGI intensity delivered to the microbes in the air stream. The air discharge velocity and air discharge pattern from the unit is important to avoid short circuiting.

As others have already stated you need at least 6 effective air changes per hour or more to have any chance of being effective but, even that is dependent ...

Gobe: We met in Boston at Harvard School of Public Health Coarse . I am a professional engineer providing services in HVAC and I am a partner in an air purification products company (L2B Environmental Systems Inc.).

In order to determine the overall efficiency of any UVGI appliance in your TB wards we would need the following data about your wards. The area of the proposed space, the volume of air delivered to the space from install HVAC equipment and placement of diffusers, whether the air delivered is recirculated or 100% fresh make-up air, the natural air exchange rate of the space or if window and doors are open and the ceiling height. To size the appliance and to determine the number of appliances required in the space the engineering specifications of the appliance is required. The air delivery rate of the appliance and the UVGI intensity delivered to the microbes in the air stream. The air discharge velocity and air discharge pattern from the unit is important to avoid short circuiting.

As others have already stated you need at least 6 effective air changes per hour or more to have any chance of being effective but, even that is dependent upon the actual site conditions and the number of people infected, etc.

In all of our applications we design based upon clean air delivery rate (CADR)and UV dose of 4000microjoules/square centimeter, which takes into account all the above parameters pertaining to site conditions and appliance design before making recommendations. If your engineer has not completed these calculations or if he/she needs help I would be happy to assist.