Preventing Ventilation-Induced Lung Injury

A new study of mice has found that pumping too much air into the lung over-distends the organ, leading to ventilator-induced lung injury (VILI).

Researchers from the University of Vermont (Burlington, VT, USA) divided mice into three experimental groups. All three groups received positive end-expiratory pressure (PEEP) and low tidal volume air. Each group was ventilated for two hours. The experimental groups differed according to how many deep inflations they received: HV (high volume) received one deep inflation each breath; LV (low volume) received two deep inflations each hour; LVDI (low volume deep inflation) received two deep inflations each minute. In addition, there were two control groups: a surgical sham, which received no ventilation, and a group that received deep inflation every breath and no PEEP.

The study found that the lungs of the mice given LVDI remained more open and functioned better than the LV and HV. The lungs of the mice that received only LV became stiff and portions of the lungs collapsed. However, lung function returned briefly to normal when the mice received their infrequent deep inflations. This suggests that the lungs self-repair after the deep inflation, at least over the course of the first two hours.

The lungs of the mice that received HV suffered overdistention injury to their lungs. This group was similar to a high tidal volume group, once again demonstrating that low tidal volume is safer. The control group that received high tidal volume but no PEEP showed the highest evidence of injury, even higher than the high tidal volume group. This indicates that PEEP helps reduce the negative effects of frequent deep inflation. The study was published in the May 12, 2006, online edition of the American Journal of Physiology-Lung Cellular and Molecular Physiology.

"There is still a lot of controversy and uncertainty about how best to ventilate the lung,” said lead author, Dr. Jason HT Bates. "One controversy is whether deep inflations, the ‘sighs' that each of us takes periodically, should ever be given, and if so, how frequently. We demonstrated it's possible to give deep breaths too frequently and too seldom.”



Related Links:
University of Vermont