Scientists at Boston University's Department of Biomedical Engineering report in about a new ventilator that varies the amount of air it puffs into a patient's lungs, in turn reducing lung damage. Long term use of ventilators, which pump air into the lungs of patients who can't breath for themselves, can damage delicate lung tissue and lead to collapsed lungs. Adopting an approach first used by researchers at the University of Manitoba, the Boston team developed a unit that slightly varies the amount of air dispensed from breath to breath. They modelled the way a damaged or collapsed lung was reinflated by a ventilator and found that if air pressure was varied, more lung tissue became exposed to air and there was better gas exchange during a breath. They are now testing a device based on this variability on animals with good results so far, according to the researchers.