"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. "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 Gilman B. Allen, Benjamin T. Suratt, Lisa Rinaldi, Joseph M. Petty and Bates in a paper entitled "Choosing the frequency of deep inflation in mice: balancing recruitment against ventilator-induced lung injury."

Allen, a medical doctor with Fletcher Allen Health Care and the University of Vermont department of medicine, has treated patients on ventilation. Bates is a University of Vermont department of medicine researcher interested in lung physiology.

The study found that the lungs of the mice given two big breaths every minute (LVDI) remained more open and functioned better than the LV and HV. The lungs of the mice that received only two deep breaths per hour (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 deep inflation every breath (HV) suffered overdistention injury to their lungs. This group was akin to a high tidal volume group, once again demonstrating that low tidal volume is safer. "We demonstrated it's possible to give deep breaths too frequently and too seldom," Bates explained. The middle ground - two deep inflations per minute - provides the most benefit to the mice we studied without injuring the lungs, he said.

MEDICA.de; Source: American Physiological Society