Bethesda, MD. (July 25, 2006) Ventilation therapy burst into the public consciousness more than 60 years ago with the "iron lung" and the polio epidemic. Mechanical ventilation has come a long way since then and is used today with patients who cannot breathe on their own because of trauma, lung injuries and chronic lung disease.
But ventilation demands a delicate balance between over inflating and under inflating the lungs, either of which can lead to further injury. Researchers have found that pumping too much air overdistends the lung, leading to ventilator-induced lung injury (VILI).
Doctors currently use small amounts of air (low tidal volume) to protect against VILI. But low tidal volumes can lead to progressive closure of the lungs' air cells, called alveoli, reducing the lung's ability to exchange gases. One way to reverse closure of the alveoli is to periodically give a more robust puff of air, known as deep inflation.
A new study in the online edition of the American Journal of Physiology-Lung Cellular and Molecular Physiology shows that low tidal volume combined with periodic deep inflation provides the best balance between keeping the lung open and preventing VILI in mice. And, using mice, these researchers have shown for the first time that although deep inflation is necessary, it can be overdone.
"There is still a lot of controversy and uncertainty about how best to ventilate the lung," said the study's senior author, Jason HT Bates of the University of Vermont. "One controversy is whether deep inflations, the "sighs" that each of us takes periodically, should ever be given, and if so, how frequently."
Researchers find optimal range
"This study demonstrates that an optimal frequency range of deep inflation delivery exists, at which point the potentially injurious effects of overdistention are outweighed by the protective benefits of maintaining a predominantly open lung," wrote Gilma
Contact: Christine Guilfoy
American Physiological Society