Electro-Magnetic Interference in Hospitals

[Buffalo]

Hi Y'All...:)

I'm putting together an EOI document for a wireless setup in a private hospital.

Although it is private, the hospital in questions does have an intensive care department and the wireless coverage is required for this area.

My question is this: Will the 802.11a/b/g devices produce enough EMI in the specific ranges neccessary to disrupt medical monitoring equipment? I mean this is a similar way that mobile phones do.

If the answer is no then I need some supporting documentation to show my findings. If the answer is yes, then I need to find a solution, and show supporting documentation.

I don't expect you guys to make my arguments for me (I want to learn about this as well), but I need some suggestions on where to start. There is a surprising lack of info on 802.11x EMI available through google - There's heaps about mobile phone EMI, but that's of limited use for my purposes.

I expect that the answer will be that it is not an issue, but considering how high the stakes are (life and death really), I need to be sure.

The main problem is not the Access Points - these are far enough away to not be an issue. What I'm more concerned about is the broadcast proximity of the client devices. These may be quite close (>1m), as doctors will be using hand held devices and ruggedised tablets at patient side.

Thanks for your help as always...:)

[sperm]

I expect you read (authoured ?) this document on the same topic:
http://www.pdamd.com/features/interference.xml
It is dated yesterday.

It was the first thing that came up when I did a search in google....

edit: heres a nasa report with test results of radiation from wireless laptops if you want specific numbers: http://techreports.larc.nasa.gov/ltrs/PDF/2002/cr/NASA-2002-cr211941.pdf

[frednurk]

http://i.a.cnn.net/cnn/2004/TECH/ptech/05/10/wi.fi.phones.ap/vert.wi.fi.ap.jpg

Laboratory tech support specialist Lee Brown talks into his Vocera 'communicator' in the emergency room area at El Camino Hospital.
This is obviously not a problem in these hospitals. Article is from CNN about the rollout of Voip stuff and the cost savings and efficiency gains. All the same wi-fi stuff though. CNN story link here (http://www.cnn.com/2004/TECH/ptech/05/10/wi.fi.phones.ap/index.html)

[Buffalo]

Originally posted by sperm
I expect you read (authoured ?) this document on the same topic:
http://www.pdamd.com/features/interference.xml
It is dated yesterday.

It was the first thing that came up when I did a search in google....

edit: heres a nasa report with test results of radiation from wireless laptops if you want specific numbers: http://techreports.larc.nasa.gov/ltrs/PDF/2002/cr/NASA-2002-cr211941.pdf

The first link is a usefull document and I did read it when I was searching. But despite the title it does only deal specifically with mobile phone interference. The document does however, give some useful resources to continue my research.

The reason 802.11a/b/g is percieved as being different from mobile phones is that it uses a different frequency range (2.4 and 5.6 Ghz), and it's emissions may be a lot stronger.

They do also mention in both articles that transmissions broadcasted from mobile phones from less that 3 feet could present a risk. The WiFi devices in our scenario could potentially be well within the 1m radius...

Still... I do have a starting point now. Please do continue to post any suggestions, and I'll post any findings, for anyone that's interested....:)

[ersatz]

interesting, I''ve got a similar wireless project for an old peoples' home, wondering if it'll mess with their pacemakers.

[Buffalo]

Originally posted by ersatz
interesting, I''ve got a similar wireless project for an old peoples' home, wondering if it'll mess with their pacemakers.

There is clearly documented evidence that analogue mobiles do cause problems with pacemakers and there are FCC guidlines that require mobile phone makers to warn end users with pace makers not to keep their mobile phone in their breast pocket.

These warning may have nothing to do with WiFi products, but there doesn't seem to be much documentation either way. As Frednurk said there are many companies already producing wifi devices that are being used in hospitals, so someone MSUT have done research, at least from the point of view of liability risk minimisation.

WiFi is specifically banned from planes, due to the risk of interference, but also due to it's potential for use as a triggering device, so it's hard to determine the weight to assignto each reason.

The reason I have to do this reasearch is not so mcuh that I am worried that it might be a problem, but more because the client has raised it as a specific concern that needs to be investgated as part of the tender.

[DumHed]

Wireless lan type devices have much lower transmitter output power than mobile phones.
Whether or not they're within the safe limits of medical equipment is another story.

Electrically though mobile phones are in an entirely different league when it comes to generating nasty interference.

[flow]

Originally posted by frednurk
Laboratory tech support specialist Lee Brown talks into his Vocera 'communicator' in the emergency room area at El Camino Hospital.
This is obviously not a problem in these hospitals. Article is from CNN about the rollout of Voip stuff and the cost savings and efficiency gains. All the same wi-fi stuff though. CNN story link here (http://www.cnn.com/2004/TECH/ptech/05/10/wi.fi.phones.ap/index.html)

Bugger. You beat me to it. I've played with one of these. I'm in the VoIP industry and yeah - there's lots of hospitals trialing setups such as this. Non in Oz tho I don't think.

WiFi's seems to be okay for hospitals. I think some country victorian hospitals are already using it with PalmPilots to check records of each patient etc...

[druid]

Originally posted by Buffalo

WiFi is specifically banned from planes, due to the risk of interference, but also due to it's potential for use as a triggering device, so it's hard to determine the weight to assignto each reason.


I'm afraid I can't help you with the actual question but hopefully little tidbits like this will help you find the right direction:

There are planes equipped with WLAN. Lufthansa for instance has a WLAN service for its passengers and I think SAS has one too. New planes and new equipment can take the extra radiation.

It is true however that some countires might have regulations banning those devices in planes.

[Drakin]

Ok while this doesnt show exactly what you were after it shows that they are addressing your issue from a different perspective.

For researching this sort of topic you need to get into whitepapers

Clearing the Way for Wireless Medical Telemetry
by Mark Gibson

In February 1998, patients in the critical care wards of Baylor University Medical Center and Methodist Hospital in Dallas, TX were briefly able to tune in The Jerry Springer Show on their wireless heart monitors. Ok - not really. What actually happened was that one of the TV stations in the Metroplex was testing their new digital television (DTV) equipment, and it happened to be in the same wireless band as the wireless patient monitors, 608 – 614 MHz. Although no patients were harmed, it knocked the monitoring systems off the air and caused quite a concern.

Medical telemetry systems consist of portable devices that monitor a patient's electrocardiograms (EKG’s) and other physiologic parameters such as hemoglobin oxygen saturation and blood pressure, and transmit this information wirelessly to a central station display or to a bedside monitor for review and analysis by clinical personnel. These systems can be installed hospital-wide, or in a specific area such as a cardiac care unit. Complete systems, capable of monitoring up to one hundred patients, can cost well over $1M.

An association representing those with interests in healthcare engineering, the American Society for Healthcare Engineering (ASHE) of the American Hospital Association, mobilized their efforts and convinced the Federal Communications Commission (FCC) to designate spectrum to a new service called the Wireless Medical Telemetry Service, or WMTS.

The FCC allocated three bands to WMTS: 608 – 614 MHz, 1395 – 1400 MHz, and 1427 – 1429.5 MHz – a total of 13.5 MHz, all of which is encumbered. In addition to the DTV stations adjacent to the 608 – 614 MHz band, there are several radio astronomy receive stations located nationwide and in both the 1395 – 1400 MHz and 1427 – 1429.5 MHz bands there are numerous military radar stations.

WMTS equipment is "Licensed by Rule" - which means that the FCC authorizes the operation of radio stations without individual licenses since operators will generally not be in competition with each other. The WMTS is to be shared among authorized medical telemetry users with no mutual exclusivity between users. Thus, the FCC qualified the rules on the use of this spectrum by the WMTS: its usage must be coordinated both with the existing users and the new WMTS users.

In April 2001, the FCC designated ASHE as the Frequency Coordinator stating that, “ASHE/AHA has singular attributes that … make it the superior candidate to oversee WMTS frequency coordination.” ASHE selected Comsearch as their technical partner to develop a system for performing WMTS frequency coordinations recognizing that, while they may have singular attributes, they still needed some help. Comsearch will provide a broad range of services to ASHE and its members including development of a WMTS device database and device registration capabilities, EMC and interference mitigation consulting, training, industry representation, and wireless consulting.

A curious aspect of this is that ASHE is not supposed to actually perform interference analyses. Their role is to collect WMTS coordinations in a database that’s open to all WMTS users, and allows the users to select frequencies from a list of those available. Comsearch’s role is to develop the database, as well as the web-enabled front end to that database. In addition, Comsearch will provide frequency coordination services to WMTS users who select frequencies that may interfere with the radio astronomy and military radar bands. In situations where there is no available frequency, Comsearch can perform an interference analysis.

Hospitals are one of the most complicated and concentrated RF environments in the world from the standpoint of electromagnetic compatibility (EMC) and electromagnetic interference (EMI). Services such as X-ray machines, MRI, CAT scan, wireless patient monitoring, paging, nurse’s call, land mobile, aviation, telephone, wireless LAN, wireless signaling, building monitoring, etc. are all profuse in the hospital environment, and all generate their own complex RF signatures that often interfere with each other. Thus, there’s a definite need to help mitigate EMC / EMI problems both before and after wireless equipment or systems are installed.

Clearly, there are exciting times ahead as we look to provide our services and offerings to these segments of the healthcare industry. We’ll be putting Jerry Springer back where he belongs: on TV. Ok – not really.

[Buffalo]

As always the ZGeek community comes through with th goods...:)

Thanks guys - All your info is extremely helpfull..

I will post my results up shortly, so stay turned if you're intersted....

Once again thanks to Drakin, Druid and FredNurk and all you guys..:)