Machine based on iron lung of 50 years ago.
Instead of forcing air into the baby's lungs, the CNEP machine provides a negative pressure around the infant's body to help breathing.
This is exactly the same way the iron lung operated. The machine, which enclosed the patient in a box in which air pressure was lowered, saved many lives during the polio epidemics of the 1950s.
It was discontinued because access to the patient was difficult and complex manipulation of ventilation impossible.
However, there are risks associated with the alternative method of positive pressure ventilation in premature babies.
Ventilation is necessary for infants who develop lung infections which may lead to pneumonia and prove fatal.
Dr Andy Petros, a paediatric intensive-care consultant at London's Great Ormond Street Hospital, said: 'The general treatment is to put a tube into the trachea (windpipe) and attach it to a ventilator which pumps air into the lungs.
'But when you put air into tiny lungs, it's a bit like blowing up a balloon, and it can cause damage. The idea of using negative pressure is that instead of blowing, you suck.'
CNEP stands for Continuous Negative Extrathoracic Pressure. The experimental system employs an incubator-like container in which the baby is placed with its head protruding through an airtight opening. Pressure inside the box is reduced, causing the baby's chest to expand so that air - or a supply of oxygen - is drawn in through its mouth and nose.
The method is supposed to reduce the chances of chronic lung damage, but its effectiveness has not yet been proved.
Prof Southall has championed the technique since the early 1990s. But his team is the only one so far to have used the machine, which is regarded warily by some other experts.