Subject: [NEXTEL-1] RF Fields in Hospitals (Phil Anderson)

From: <[email-masked]>
Date: Sat, 22 Nov 2003 17:30:02 -0500

From: "Robert Weller" <[email-masked]>
Date: 2003/11/22 Sat PM 05:17:12 EST
Subject: RF Fields in Hospitals (Phil Anderson)

Interference to modern pacemakers?  Very unlikely.  There 
have been a number of papers published on that possibility 
(In J. Pacing and Clinical Electrophysiology and by the 
Wireless EMC Center at U. Oklahoma, among others) that 
indicate interference is possible only at exceptionally 
high field strengths.  Write if you want the specific 
references or details, I don't have them with me at the 
moment.    

There was a short article published last month in the 
magazine, Compliance Engineering, that I believe documents 
field levels in hospitals.  I do not know whether a cell 
phone base station was nearby.  I have personally made 
measurements in at least 6 hospitals with cell base 
stations on the roof.  None of them had internal fields, 
attributable to the cell site, that exceeded 1 V/m.  Most, 
but not all, equipment certified for use in hospital 
environments is immune to upset at field stengths of up to 
 3 V/m.  
 
WRT your WLAN question, I am aware of no specific studies, 
but most WLANs operate as unlicensed devices, meaning that 
the allowable field strengths are very low.  I doubt that 
one would encounter field strengths exceeding 3 V/m even 
at a few cm from the antenna.  Much patient telemetry 
equipment emits at levels greater than this.  

The biggest interference threat in hospital environments 
probably is to/from the wireless telemetry equipment used 
for patient monitoring.  Much of that equipment uses VHF 
and UHF narrowband frequencies on a shared basis with 
other services.  There are no guarantees that interference 
will not, from time to time, occur.

Bob Weller
Hammett & Edison
San Francisco

Message: 1
From: "Phil Anderson" <[email-masked]>
Date: Sat, 22 Nov 2003 12:26:25 -0500
Subject: PROP-L:RF Fields in Hospitals

Hello to all:

	I have enjoyed this forum for the last 3 years but 
haven't opened my mouth
till today.

	It is quite common for cell phones to be banned inside 
hospitals because of
the possibility of RF interference to things like pace 
makers. Does anyone
know of any studies of field intensities inside hospitals 
due to cellular
antennas on the roof of the same hospital?? It is my 
experience that there
is usually a very good signal from these antennas inside 
critical areas
within the hospital.

	Second question, does anyone know of any study of RF 
field intensity due to
wireless LANs inside hospitals and the impact on 
sensitive equipment such as
ECG and pacemakers etc?? It is not unusual that a 
portable computer with a
wireless LAN is pushed around on a cart to various rooms. 
These don't seem
to be banned.

	Thanks

	Phil Anderson
	Prof University of Guelph/ Humber College
	Toronto Ontario

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