Last updated at 08:46 05 March 2007

Routine use of oxygen for heart attack victims

could do more harm than good, it is claimed.

Many patients receive oxygen after a cardiac

arrest to reduce the workload on their heart.

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But Professor Richard Beasley, from New

Zealand’s Medical Research Institute, said it was

vital that "clinical dogma" over the practice is

challenged.

Writing in the Journal of the Royal Society of

Medicine, he said: "Research in this area is

scarce but cardiologists should be concerned as

the balance of evidence suggests that its routine

use in this clinical situation may cause

harm."

He warned that it could reduce blood flow and

cause more heart damage.

However the British Heart Foundation said use

of oxygen after a heart attack was current best

practice and there was not enough evidence to suggest medics should now stop giving it to

patients.

Some heart attack victims develop hypoxaemia,

which is low oxygen levels in the blood.

To overcome this doctors and paramedics can

give them extra oxygen to breathe via a face

mask.

However, in practice many patients are given

oxygen after a heart attack whether or not the

level of oxygen in their blood is low.

Professor Beasley said the only controlled trial

of oxygen therapy in the first 24 hours of a heart attack, carried out in 1976, showed that patients receiving it ended up with greater heart

damage than those receiving room air.

He also pointed to a 2005 study which showed

that treating patients with high-flow oxygen

reduced blood flow through the coronary

artery.