"We can now administer the same or even smaller doses of drugs but achieve prolonged effectiveness," said Yang, an associate professor at the university's School of Chinese Medicine.

"An inhaler that can usually be used for a month can now be used for about three months."

Traditional inhalers were only as effective as their user's lung capacity, Yang said. But since high doses of medication would harm the membrane of the respiratory tract, patients were usually prescribed limited doses every four hours to ensure a sustained therapeutic effect, he said.

With the new system, however, the medicine is transported in tiny non-breakable molecular substances called liposomes, which cling to the lungs and prevent rapid loss of the drug through the blood or exhalation.

Previous tests on rats documented in the in 2012, showed that drugs encapsulated in liposomes could remain in the lungs for up to 48 hours.

Yang said traditional forms of drug delivery, such as tablets taken orally, injections or traditional inhalers, were not always as effective as believed.

Tablets contain high doses of drug and often come with side effects, but are effective for only about four to six hours, he said. Injections are better, as they circulate medication throughout the body via the bloodstream, but the method is inconvenient, Yang added.

Chronic obstructive pulmonary disease, which includes chronic bronchitis and emphysema, is the city's fifth biggest killer disease.