Patients with chronic lung disease are being denied intensive care treatment because doctors are too pessimistic about their chances, research suggests.
A British Medical Journal study of 800 patients admitted to intensive care to help them breathe found survival rates were higher than doctors predicted.
It suggests patients may not be admitted when they would benefit from treatment, the researchers warned.
Chronic obstructive pulmonary disease causes 30,000 deaths a year in the UK.
COPD is an umbrella term for a range of conditions including chronic bronchitis and emphysema.
When patients have a COPD attack, they can benefit from intubation - where a tube is put into their airway to help them breathe - but they have to be admitted to intensive care so they can be sedated for the procedure.
But doctors may be unwilling to admit patients who have a poor prognosis.
The study, which took place in 92 intensive care units in the UK, found that 62% of patients who were intubated were alive 180 days later.
However, doctors had originally predicted less than half would survive that long.
In patients with the worst prognosis, the doctor predicted 10% survival at 180 days but in fact 40% of patients lived this long.
Study leader Dr Martin Wildman, consultant in respiratory medicine at Northern General Hospital in Sheffield, said in an averagely-sized hospital the decision to admit a patient with COPD to intensive care probably happens once a week - or two to three times a week in winter.
"Some clinicians have the perception that if patients did survive they would have an awful level of function and would be miserable.
"But other research shows most patients who survive would choose to be intubated again."
He added that in the 1990s patients were often not admitted because there were not enough intensive care beds, which may have lead to a culture of not admitting patients.
But he also said there had not been the evidence of how successful intensive care could be until now.
Dr Noemi Eiser, medical director of the British Lung Foundation, said: "It is sad to see evidence of such widespread pessimism about the survival prospects for people with COPD amongst clinicians.
"It's to be hoped that better awareness of the disease in the years since this study was carried out should have reduced such negativity, particularly when more effective non-invasive treatments are becoming more widely available.
"The research also reminds us that around four in ten patients admitted to hospital for flare-ups of their COPD are dying within six months of discharge." ( BBC )