British doctors fear that plane journeys to and from hospitals in Germany and France could put Britons' health at risk

The health of NHS patients flown to German hospitals for treatment could be put at risk during the journey, according to one of health chiefs involved in the new initiative.

On Friday, West Sussex Health Authority flew the first three patients to Essen, Germany, for full knee replacements. More patients are due to go out later this week. But Dr Peter Old, chief executive of another health authority taking part in the pilot scheme, said he would be unhappy to fly back his patients after major orthopaedic surgery.

He said the patients were not only at increased risk of deep vein thrombosis but also their recovery could be jeopardised by the cramped seating on airlines.

In all, 200 patients will be sent to France and Germany as part of the Department of Health trials. But if there are dangers in moving patients by plane, the scheme, which the Government hopes will cut hospital waiting lists in the UK, would be in serious doubt.

The first patients – sent to Lille in northern France two weeks ago – travelled by train so issues of DVT and very cramped seating did not arise.

"We have some difficulty in transporting those sorts of people by plane," said Dr Old, chief executive of Isle of Wight, Portsmouth and South East Hampshire health authority. "It would be difficult to envisage somebody after a knee or hip operation sitting on a plane."

His own health authority is flying up to 59 patients to Germany but they will be only less serious cases such as those needing foot operations. "We are sending a group of 'intermediate' cases because we want to test the system," he said. "It's not the going out that I'm worried about but the coming back." He wanted "reassurances" before contemplating sending patients needing more serious operations. He also expressed concern West Sussex patients had not been seen by the German surgeon before being flown out. His health authority will fly the German surgeons to the UK first to assess patients.

It is conceivable a surgeon seeing an elderly patient for the first time in Germany may decide surgery is not suitable. The patient would then have to be flown back to the UK without the operation.

Dr Old's fears over DVT were backed by an expert in the field. Charles Forbes, a university professor based at Ninewells Hospital in Dundee, said he would not choose to fly home after an operation abroad although he thought with the right drug treatment the risks were "not a big problem". "I personally would not go on the plane. I would find some other way," said Professor Forbes.

A West Sussex health authority spokesman said patients were staying in Germany for three weeks after the surgery so they are "fully fit when they fly do back".

One patient flying to Germany said she was just pleased to have a knee replacement operation after a 15-month wait.

"I'd rather take the opportunity now than hang on here waiting," said Elisabeth Ashcroft, 80, from Chichester. "I'm due to leave on Friday, but they're still not able to tell me which hospital I'm going to, or which day the operation will be. Apparently it will be either Essen or Cologne."

Mrs Ashcroft, who will be accompanied by a translator but has been given a German dictionary by her daughter "just in case", added: "If the English doctors are satisfied, I am satisfied. I'm going to be staying there for at least three weeks, with post-operation physiotherapy included."

Mrs Ashcroft is already packing for her trip. "And at least the weather should be better over there," she said.