Thousands of medical devices in patients' houses and nursing homes have slipped through a hole in the NHS Executive's year 2000 programme, it emerged last week.

Because home-based instruments are issued by many different organisations inside and outside the NHS, nobody knows who is responsible for testing their year 2000 behaviour, according to consultant Martin Whittaker of the Executive's millennium bug team.

And until now, nobody has taken steps to ensure that every home device will be covered by one or other of the possible bodies.

'Patients are beginning to get worried about this. Some are writing to their MPs,' Mr Whittaker told the Healthcare Computing Conference in Harrogate.

'But no-one even has any idea how many home-based devices there are. They range from dialysis machines, oxygen concentrators and intravenous feeders to blood pressure meters and glucose monitors for diabetics.

'Some of those in circulation have been bought by patients themselves, on the advice of nurses, and many more are in private nursing homes.' Certain critical devices are already covered.

The Medical Devices Agency has taken responsibility for implanted pacemakers and all of these are believed to be year 2000-proof, said Dewinder Bachu, MDA senior device specialist.

But some critical devices - including dialysis machines - are in limbo. 'I assume that trusts know where all these are, but it isn't yet clear that they have the problem well up on their priority lists,' said Mr Whittaker.

Jim Crawley, year 2000 project manager at Royal Hull Hospitals trust, said acute trusts in Yorkshire had prepared lists of vulnerable home patients.

But he pointed out that some of the larger home devices are dependent on continuity of utility supplies, especially electricity. This is beyond trusts' control.

The conference was told that responsibility for the devices needs to be sorted out 'before the press gets hold of this'.

But the Executive insists that the problem is not life-threatening.

'There is a difference between the perception and the reality of these risks,' said Mr Whittaker.

A circular is about to go out nominating responsible health bodies and ensuring that no category of device 'falls through the cracks', Mr Whittaker said.