New treatments for some lung diseases are a step closer thanks to research that pinpoints why existing drugs are "ineffective", according to scientists.
The discovery could lead to better therapies for ailments such as chronic bronchitis and emphysema, researchers said.
These conditions can fail to respond to the most widely-used treatments, glucocorticoid drugs (GCs).
The study sheds new light on the complex biological processes that cause lung inflammation, the immune system's response to disease caused by bacterial infection.
Scientists analysed blood samples, focusing on the vital role that certain white blood cells, called neutrophils, play in fighting infection.
Neutrophils normally only have a lifespan of a few hours but, when they are called into action at sites of inflammation, they can survive for several days to carry out their protective functions. In doing so, they absorb more oxygen than usual.
But the Edinburgh scientists have found that GCs can be ineffective because, at inflammation sites, there is not enough oxygen for the drugs to function efficiently.
Treatments that are less reliant on oxygen supply are therefore more likely to be effective, researchers said.
They made their finding by taking neutrophils from the blood of healthy volunteers and studying the effect that oxygen had on the lifespan of the cells.
When there were healthy levels of oxygen in the blood, the drugs could keep the cells alive for longer.