Ventilators could potentially be affected
Lifesaving equipment in hospitals may be switched off by radio-frequency devices used to track people and machines, Dutch scientists claim.
Radio frequency identification devices (RFIDs) are on the rise in healthcare, helping identify patients, and reveal the location of equipment.
The Journal of the American Medical Association study found they could interfere with machines.
But NHS computer specialists said RFIDs could eventually make patients safer.
There are two types of RFID, one which transmits information, and another, "passive", device which can be "read" by a powered machine when it is held nearby.
They are small and cheap enough to be in everyday use in society, in everything from security and travel cards - such as London Transport's Oystercard, to anti-theft devices on goods in shops, and hospitals are starting to become aware of their potential.
At Heartlands Hospital in Birmingham, patients heading for the operating theatre wear an RFID wristband, so that even when anaesthetised, their full identity, including a picture, can be downloaded into a PDA held nearby.
The latest research, conducted at Vrije University in Amsterdam, tested the effect of holding both "passive" and powered RFID systems close to 41 medical devices, including ventilators, syringe pumps, dialysis machines and pacemakers.
A total of 123 tests, three on each machine, were carried out, and 34 produced an "incident" in which the RFID appeared to have an effect - 24 of which were deemed either "significant" or "hazardous".
In some tests, RFIDs either switched off or changed the settings on mechanical ventilators, completely stopped the working of syringe pumps, caused external pacemakers to malfunction, and halted dialysis machines.
The device did not have to be held right up to the machine to make this happen - some "hazardous" incidents happened when the RFID was more than 10 inches away.
Dr Donald Berwick, from the Institute of Healthcare Improvement in Cambridge, Massachusetts, said: "Design in isolation is risky - even the most seductive technology will interact in the tightly-coupled healthcare world in ways physicians and other members of the healthcare team had better understand, or they and their patients may pay a dear price."
A spokesman for NHS Connecting for Health, which manages various IT projects across the health service, said that RFIDs had the potential to deliver big improvements in patient safety, reducing mistakes caused by the wrong identification of patients.
She said: "Any product such as this which is for use in a healthcare setting has to meet a standard which means it is very unlikely to interfere with medical equipment.
"This risk is more likely to come from RFID tags from other sources - such as a travel card, a tag on clothing, or on another retail item."
A spokesman for the Medicines and Healthcare Products Regulatory Agency said that, as for mobile phone use, individual Trusts needed to make risk assessments about the use of RFIDs.
He said: "Despite much debate in the literature on the subject of electromagnetic interference (EMI) of medical devices by mobile telephones and other sources of radiofrequency transmission, the MHRA has received very few reports of adverse events caused by this problem over the last seven years or so.
"Of those incidents reported, only a very small number have been proven to be as a direct result of EMI."