The country's medical devices watchdog warned about dangers arising from faulty or wrongly-used anaesthetic breathing systems – used to keep patients alive during major operations.

In a medical devices alert, the Medicines and Healthcare Products Regulatory Agency (MHRA) said it "continues" to receive reports of patient harm because of the problems. These happen on average "less than five times" a year, a spokesman said.

"We are not aware of any device-related deaths in the past five years," the watchdog added.

Overall, about 250 incidents are reported involving anaesthetic machines each year, the MHRA said, "usually related to the way the equipment is used rather than a fault in the device itself".

In one case an anaesthetic breathing system was wrongly connected to the gas outlet of an anaesthetic machine.

When the patient started showing signs of distress, doctors wrongly interpreted it as bronchospasm, or tightening of the airways, and administered drugs.

By the time they realised there was a problem with the equipment, the patient suffered a collapsed lung but survived thanks to the prompt action of the surgeons.

In its alert, the MHRA warned: "Whilst such equipment issues are uncommon, they should be considered as a matter of course when problems with patient ventilation occur."

An estimated 3.5 million operations a year are carried out under anaesthetic.