Isolation rooms for MDR TB patients - Window and design details
Started by Ana Serralheiro on 05 Jun 2009
Last edited by Sophie Beauvais on 30 Oct 2009
Hi all,
Can someone provide information on the design of isolation rooms for MDR TB patients in order to maximize natural ventilation? Is there any standards/guidelines available?
It would be very useful to read about the following specifications:
- Windows design and placement
- Mixing ventilation vs displacement ventilation
- Ceiling high (3.5 to 4m).
- Ceiling shape (sloping ceiling vs triangle symmetric, etc)
Does someone know if there's any software/program that can be used to simulate ventilation in a room? By changing windows aperture, placement, size, disposition, etc and wind?
Thanks for all
Best
Ana
Ana Serralheiro
Infection control Specialist, MSF Geneva
Swaziland
Attached resource: Minimum requirements for building TB facilities in warm climates
Keywords: Engineering Controls, Natural Ventilation, TB IC Guidelines, Technical Consultants
Edward Nardell, MD
Hi,
I believe WHO is producing a document that may have some of what you
need. The problem with natural ventilation is that it is highly
specific to the exact environmental conditions of the site and it is a
bit difficult to generalize. Ideally, you need an engineer and architect
experienced in the application of natural and mechanical ventilation, as
well as germicidal UV.
There is a course this summer at Harvard School of Public Health,
co-sponsored by CDC, WHO and others, which spends 2 weeks reviewing
these issues in detail for architects and engineers. Several MSF
participants are coming.
I have copied Fabio Scano at WHO and Paul Jensen at CDC who may know
more about the WHO document on natural ventilation and how to get it.
Ed
Edward A. Nardell, M.D.
Associate Professor
Harvard Medical School (Medicine; Global Health and Social Medicine)
Harvard School of Public Health (Environmental Health; Immunology and
Infectious Diseases)
Brigham and Women's Hospital
Divisions of Global Health Equity and Pulmonary Medicine
FXB Building, 709c
651 Huntington Ave.
Boston, MA 02115
11:45 AM, 7 Jun 2009 | Permalink
Menno Goedhart
Dear Ana,
As there are no guidelines yet, especially for TB buildings in warm
climates, MSF drafted a small guideline for their field teams which
contains minimum requirements for building TB facilities.
The document gives a guide to building and to general infection control.
Comments welcome.
kind regards,
Menno Goedhart
Field Support Unit
MSF OCA (Operational Centre Amsterdam)
File "med-minimum req tb constructions-oca-may09.pdf" here: http://www.ghdonline.org/ic/resource/minimum-requirements-for-building-tb-facilities-in/
4:58 AM, 8 Jun 2009 | Permalink
Catherine Noakes
Dear Ana,
Following Ed's comments, I agree - natural ventilation does complicate the design of such rooms as the inherant variability induced by reliance on the outdoor conditions means that guaranteing airflow and pressure conditions in isolation rooms is much harder.
Your isolation room design has two purposes
(1) to minimise transmission to people outside the room - achieved in conventional isolation room design by creating a pressure gradient with the ventilation system to ensure flow is into the room (ie room is at negative pressure)
(2) to minimise transission to anyone inside the room - best achieved by designing an airflow that is fully mixed to avoid high risk regions and has a high dilution rate to quickly remove airborne pathogens.
The first is the hardest to acheieve with natural ventilation (mixing can always be promoted by fans) as pressure gradients will depend on the prevailing wind, indoor-outdoor temperature gradients and the building design and orientation. With the best will in the world there is always a risk of flow reversal in a naturally ventilated system ( usually the wind blows the other way!) and it is likely that some kind of fan assist will be necessary for high risk applications such as this.
In terms of modelling ventilation - yes it is possible although not that easy. Computational Fluid Dynamics (CFD) is a tool that is increasingly being used to look at airflow in buildings and risk of infection. It is a specialist tool that requires expert knowledge to use correctly and once again natural ventilation complicates the whole issue as it is harder to define how and where air enters and leaves the room. We have quite a bit of experience in using this software and also have just started a major project looking at optimising ventilation for hospital accomodation. Although we are primarily looking at UK hospitals (balancing energy agenda with infection control) your case is interesting and could fit in our remit. Please get in touch (details below) if you would like to talk more "off-line"
Best regards
Cath
==================================
Dr Catherine Noakes
Pathogen Control Engineering Institute
School of Civil Engineering
University of Leeds
Leeds, LS2 9JT, UK
5:40 AM, 8 Jun 2009 | Permalink
Ana Serralheiro
Hi Edward,
Thanks for the reply. One of the issues here is that the environmental conditions change dramatically during hot and cold season and make it very difficult to adjust the building design in order to reduce the cold in winter when the windows are open.
In there any list of engineers and architects experienced in the application of natural and mechanical ventilation, germicidal UV, etc?
Thanks for the information about the training in Harvard,
Ana
Ana Serralheiro
Infection control Specialist, MSF Geneva
Swaziland
Thanks
4:24 AM, 9 Jun 2009 | Permalink
Ana Serralheiro
Hi all,
Following Menno's reply, thank you very much for the guidelines, they have shown to be very useful till the moment.
Thanks Catherine for your reply as well.
I agree with you, the reliance on natural ventilation highly increases the complexity of the rooms' design because the airflow direction and changes in pressure is unpredictable. Particularly here in Swaziland that the weather conditions change much between winter (5 C) and summer (35 C).
Considering the limitations of mechanical ventilation, special in the present scenario in Swaziland, and based on previous evidence on the efficiency of natural ventilation to prevent the transmission of airborne diseases, we have shifted our approach away from the conventional design of isolation rooms (i.e. negative pressure).
We are presently designing the isolation rooms for suspected and confirmed MDR patients as individual rooms, with windows/doors directly open to the outside area. In the present structure there will be no indoor corridors and all the common areas will be outside.
The rooms disposed in parallel with maximization of cross-ventilation through windows/doors in opposite walls.
With this approach we intend to minimise the transmission to anyone outside the room (1) without the need to control the pressure gradients between the rooms and other areas.
To minimize the transmission inside the room (only frequented by HCW) we want to maximize the natural ventilation and air dilution by “playing” with the room design (selling high/design, windows design/placement, etc).
As you suggested, it would be very interesting to use the Computational Fluid Dynamics (CFD) tool to analyze the change of airflow in the room with the placement and aperture of the windows, ceiling high, etc.
I will get in touch with you to discuss further on this subject,
Best regards
Thank you for the feedback,
Ana
Ana Serralheiro
Infection control Specialist, MSF Switzerland
Swaziland
2:57 AM, 10 Jun 2009 | Permalink
Edward Nardell, MD
Ana and all,
I think your approach is great. I believe they follow these exchanges, but if not, I have copied Michael Murphy, an architecure student who is doing some CFD on a naturally ventilated hospital for PIH in Rwanda, and Hans Mulder, another architect who has designed hospitals using natural ventilation in Namibia. Perhaps they will comment.
My suggestion is that even without full ventilation systems, you consider exhaust window fans both to insure adequate air exchanges when the outside air is still, and to provide some directional airflow if the windows have to be closed for cooler temperatures or for security.
Ed
9:08 AM, 10 Jun 2009 | Permalink
S. Mehtar
Hello Ana
We are helping in Swazi with a TB-IPC programme including containment. I am delighted to see that MSF is tackling the hospital design side of it so effectively. I would love to talk to you about it.
Best Regards
Shaheen
Prof Shaheen Mehtar
MBBS, FRC Path (UK), FCPath (Micro) (SA), MD (Eng)
Head of Academic Unit for Infection Prevention and Control
Tygerberg Hospital & Stellenbosch Uni
PO Box 19063,
Tygerberg 7505, Cape Town
10:45 AM, 10 Jun 2009 | Permalink
Paul A. Jensen, PhD, PE, CIH
Greetings all!
This has been a great discussion! I would like to make a comment about the efficiency of natural ventilation to prevent the transmission of airborne
diseases. I am not aware of any epidemiologic data to support this statement. There have been studies using tracer gases that show the. benefits of both natural ventilation and mechanical ventilation. There are many epidemiologic studies showing that when a ventilation system is not working properly, air flows down the corridor and transmission occurs. And now we can add UVGI to the table! Unfortunately, when is comes to data to support engineering control recommendations, there is a void. We rely on expert opinion and extrapolation.
So, what is the solution? Do the best you can with what you have! If a building can be modified to maximize simple natural ventilation during cool weather, do it. You could even give the patients extra blankets! Also, will the windows be maintained and open? If not, think how to overcome this problem. Are they designed to be open during adverse weather (rain, etc.)? Are the windows designed/located to minimize draughts?
Now there is expensive, complex natural ventilation that could work in cooler environments and partially control air flow; however, the capital cost will be more than complex mechanical ventilation.
How about simple exhaust ventilation? It has the potential for working if designed correctly. I have been in numerous facilities with exhaust fans AND open windows. Why even turn the exhaust fan on? I have also been in a few facilites with exhaust fans and doors that fit relatively tightly. In that case, the fan goes around-and-around, creating negative pressure; however, there is neither airflow nor dilution! So, exhaust-only ventilation needs a source of air (not necessarily a mechanical supply). This could be an opening under the door )2-3 cm) or a small screen in the door panel. Now, you have to ask yourself what's on the other side of the door? Is it a waiting room with infectious patients? I hope not! If yes, how else can you get relatively clean air.
Also, in simple natural ventilation and exhaust-only ventilation, the equilibrium temperature in the occupied spaces will approach that of the out-of-doors (assume good air exchange rates). So, if it's 5C outside, it will be cool inside. If it's 40C outside, it will be warm inside. Hal Levin has coined the phrase "building ecology." Building ecology takes into account the "relationships and connections between buildings, occupants, and the larger environment . . ." We need to deal with all three entities and not focus only on ventilation!
Bottom line: if one looks at each situation with an open mind and asks a lot of "what if" questionsn and I am certain you will come to the best solutions (note . . . more than one)!
Sorry for being so wordy . . .
Regards,
Paul J
--------------------------
Sent from my BlackBerry . . . Please excuse my fumbling thumbs!
11:32 AM, 10 Jun 2009 | Permalink
Thea Zuccotti
Hi Ana and everyone,
I find the subject of the present discussion very interesting and challenging… in fact it is about low budget-easy maintenance IC response to be applied in a “cool” climate.
I would like to make you a short update on some studies I am (-we are, see below) working. I think those studies could be helpful to your case as well.
In April at the 35° TSRU (Tuberculosis Surveillance Research Unit) congress I have been presenting a little research whose title is “Low budget environmental controls in cold settings, economical comparison between natural ventilation and UVG lights”. The case study analyzed have been a little (90 sqm) rural clinic in Lesotho. In the conclusions of that preliminary research you can read: “[…] the natural ventilation system is about 15 times [economically] more convenient then the UVG one. Furthermore, the considered location gives room to invest in a climatic responsive building, for example, exploiting the offered high sun radiation. […] Using a NV system as environmental IC if not properly designed, could be not effective at all and it could give a false sense of security to the inhabitants. For example, when air patterns are not controlled through a proper air-flow direction and a proper air-mixing in each room, the inhabitants are not safe. […] [The NV system should be analyzed] on two levels: the IC (ensuring the 6 ACH) and the solar building [design]. In this way it will be possible to give a sustainable answer to control infection from air born diseases in a cold setting.”
At the moment I have built a technical working group: Dott. Brunetti (Architect, specialized in solar building design), Dott. Adhikari (Physicist, specialized low energy technologies in building applications) both are Researchers and Lecturers at the Politecnico di Milano. And me, Dott. Zuccotti (Architect, specialized in health structure design and IC techniques).
Considering the results obtained with the preliminary research, we aim to study deeper the natural ventilation system (applied to the Lesotho rural clinic) with a particular attention to: the air fluxes design and control (using exactly the CFD software) and to the solar building design (using high resolution thermal models) to control as much as possible heat losses during winter time.
Reading this discussion, we have been looking briefly at Swaziland climatic conditions: Swaziland has 4 different climatic zones, therefore it would be important to know exactly where is located your clinic, but it doesn’t look impossible to apply the same concept of sustainable solution (natural ventilation and solar building design) to your clinic as well.
For the moment we are searching funding to develop the study as described here above. If you are interested I will keep you updated on the evolutions.
Thea
Arch. Thea Zuccotti
Specialist Consultant in
Health Structure Design
10:30 AM, 12 Jun 2009 | Permalink
Donald Milton
Dear Colleagues,
This interesting discussion reminded me of some photographs of Johns Hopkins Hospital, taken in the late 19th century when buildings were all passively ventilated, and when exposure to outdoor air was considered important therapy. I found copies on Flickr and put a few links below. In the photos you can see the use of awning windows, allowing them to be open even during rain, high ceilings, and very large windows. On the roof were stacks that were designed to maximize the building's stack effect. The interior photo of the octagon building shows that the inlets for the central stack were placed near the ceiling of the room, so as to conduct the hot air their up and out of the stack, thus increasing the intake of air through the windows, regardless of the wind direction. In the spirit of "there's nothing new under the sun", it might be useful for modern CFD folks to take a look at the designs used back then -- those Hopkins buildings were once the state of the art, but the art has probably been forgotten. Regards, Don Milton
links:
http://www.flickr.com/photos/medical_archives/3593134412/
http://www.flickr.com/photos/medical_archives/3589874860/
http://www.flickr.com/photos/medical_archives/3589874788/
6:31 PM, 12 Jun 2009 | Permalink
Edward Nardell, MD
Thanks Don,
These principles, including stacks, are very much alive and well today
and in use in many countries. I am impressed with the interior of the
octagon ward from a transmission control perspective, given that
separate rooms were not common at that time.
Another wonderful historical reference is the 1912 book by Carrington,
"Fresh Air and How to Use It" detailing the various designs for sleeping
porches in use both at Sanatoria and in homes. In fact, many if not most
screened porches so common on US homes built in the 20's were built as
or inspired by the desire to keep TB patients outside as therapy - not
for infection control. Copies of this book can be found on Amazon, but
be careful not to buy the Xerox version.
Ed
Edward A. Nardell, M.D.
Associate Professor
Harvard Medical School (Medicine; Global Health and Social Medicine)
Harvard School of Public Health (Environmental Health; Immunology and
Infectious Diseases)
Brigham and Women's Hospital
Divisions of Global Health Equity and Pulmonary Medicine
FXB Building, 709c
651 Huntington Ave.
Boston, MA 02115
7:45 AM, 13 Jun 2009 | Permalink
Michael Murphy
Dear Ana
Sorry to only get to you now. i think your approach is, as Ed mentioned,
great. And i agree that having good stack ventilation in the room connected
to exterior circulation and common areas could be enough to mitigate and
reduce your nosocmial transmission rates. Our designs in Rwanda are similar,
and the exterior circulation a key element of that. What we don't have in
Rwanda however is the variation in temperature that you have in Swaziland;
and so, I agree with Ed here that it would be good to have a backup system
to counteract the human variable which could close the window, unless,
through design, you can resist that variable through inoperable windows or
other fenestration options that don't overly freeze the patient. Maybe think
about open, tall ceilings and inoperable, upper-level vents in addition to
your existing stack system if you cannot include a negative pressure system.
Best regards
Michael Murphy
5:31 PM, 24 Jun 2009 | Permalink