Subject: [NEXTEL-1] Emergency radios can jam patients' lifelines

From: [email-masked]
Date: Fri, 29 Nov 2002 22:37:46 EST

<A HREF="http://www.newscientist.com/hottopics/tech/article.jsp?id=99993083&sub=Medical">http://www.newscientist.com/hottopics/tech/article.jsp?id=99993083&
sub=Medical</A>

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<A HREF="http://www.newscientist.com/hottopics/tech/article.jsp?id=99993083&sub=Medical">Emergency radios can jam patients' lifelines</A> 
A two-way radio system being widely adopted by emergency services is more 
likely to interfere with critical medical devices than cellphones

        Emergency radios can jam patients' lifelines 
By Barry Fox A two-way radio system being widely adopted by the world's 
emergency services is even more likely to interfere with the safe operation 
of some life-critical medical devices than the cellphones which are banned 
from hospitals, says a British government safety regulator.

The warning comes from the Medical Devices Agency, which has found that Tetra 
radios can upset heart pacemakers, confuse defibrillators, and stop 
ventilators working. Tetra - the Terrestrial Trunked Radio System - is being 
adopted by emergency services in 50 countries in Europe, Africa, Asia and 
Latin America.

The MDA's findings came as part of a wider study of the effects of radio 
interference on hospital equipment. The agency tested a wide range of radio 
devices by moving them steadily closer to critical items of medical equipment 
and observing the results.

Wireless communications devices such as the microwave-based Wi-Fi system used 
to connect laptops to the Internet caused few problems because they transmit 
at very low power. But some radio handsets interfered with medical equipment 
from as far as three metres away. 

In nearly half these cases the effect was serious and could have "direct 
impact on patient care", the MDA concludes. Some medical devices which were 
immune to cellphone interference were affected adversely by Tetra radio 
handsets.

Sounding the alarm 

The MDA published its results on its website in 2001, and also faxed it as a 
safety newsflash to hospitals. Now the agency is worried that its findings 
have been ignored. Most concern over Tetra has focused on the alleged health 
effects of its signals, but Andy Smith, head of critical care at the MDA 
believes interference poses the greater risk.

Tetra is a European standard that operates at a frequency of 400 megahertz, 
which is below the microwave range used by cellphones. Both systems send the 
voice data in pulses, but while cellphones send 217 pulses per second, Tetra 
has a pulse rate of only 17.6 per second. This makes it less susceptible to 
radio interference - vital for police, fire and paramedic services.

Experts believe Tetra's low pulse rate is more likely to cause interference 
than a cellphone because it is hard to filter out. In the MDA's tests, Tetra 
set off alarms on infusion pumps, while cardiac monitors went haywire and 
ventilators had to be shut down and rebooted to clear errors induced in 
software. 

An alarm on one device was unaffected by a cellphone but sounded when a Tetra 
handset came close. Even a printer was affected, and started up of its own 
accord.

Transmission inhibition 

Niall O'Malley, a spokesman for Motorola, one of the many companies making 
Tetra equipment, points out that the company offers an option called Transmit 
Inhibit. 

This can be used to restrict Tetra use inside a hospital building, say, to 
receiving calls, not sending them. But this requires the user to remember to 
switch off transmission before they enter a critical area like an intensive 
care unit.

The MDA is planning to test the effect of Tetra antennas mounted on hospital 
roofs. "These will have to focus the radio beam tightly so that it does not 
hit the ground for 60 metres," says Smith. But it may still have line of 
sight through a window and into a ward. "Hospitals are getting worried about 
this," says Smith.

Britain's National Health Service still plans to adopt Tetra. But the NHS had 
made no comment on the MDA alert by the time New Scientist went to press. 
Smith says hospitals that have moved to Tetra should carefully manage its use 
in critical areas. 

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From New Scientist Online News  10:10 22 November 02

    
    
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