When a patient suffering from an acute lung injury enters the intensive care unit, the intensity of the injury is not the only factor that may affect their mortality. Researchers at Hopkins School of Medicine have discovered that using the optimal breath size and pressure settings on mechanical ventilators is essential to the long-term health of these patients.
Acute lung injuries (ALIs) have causes, including aspiration of food or drink, trauma, such as drowning, pneumonia and drug overdose. The most intense of form of ALI is acute respiratory distress syndrome.
The lungs of those with ALIs are very weak, and these patients must therefore use ventilators to breathe. Still, around 40 percent of the 190,000 ALI patients in the United States die in the hospital every year.
The mortality rate for ALI patients is so high because of the impaired function of the inflamed and destructed lung tissue. There is only a limited amount of functioning tissue left that is still able to fulfill the body's oxygen demands. As a result, this shrunken amount of healthy tissue becomes stressed under large breaths.
The Hopkins critical care researchers discovered that by pumping only small breaths through the ventilator tube and into the patient's lungs to keep the amount of stress and pressure down, patient death rates could be reduced by up to eight percent.
These treatment methods will not only affect in-hospital care but also continued health afterward, meaning that the almost 60 percent of ALI patients who are at high risk for death during the two ensuing years can be helped.
The importance of lung-protective ventilator settings is not exactly news; researchers have known for some time that these settings may increase short-term survival, in part by reducing inflammation and in allowing other vital organs to operate properly.
However, the Hopkins researchers discovered that 59 percent of the 6,240 ventilators examined during this study were not functioning under the lung-protective settings.
In fact, they also showed that with each unit increase in the ventilator's tidal volume during the patient's stay at the hospital, the mortality risk over two years rose a frightening 18 percent. Tidal volume is the amount of air one normal inhales and exhales without exerting extra effort. It is measured in milliliters per kilogram of patient predicted body weight.
Reasons for the lack of ideal treatment include the challenge of rapidly recognizing an acute lung injury before starting standard treatment and generating a proper tidal volume setting.
The study, which was published in the British Medical Journal, examined over 450 cases of patients with acute lung injury during their time in the ICU at one of four Baltimore hospitals. Moreover, the researchers continued to study the patients, most of whom were over the age of 50, for two years after their treatment.
The National Institutes of Health and the Canadian Institutes of Health Research funded this research. Further study will involve "quality of life" analysis for patients past the two-year mark, so that ventilator effects can be more closely examined, and long-term patient health may be improved.
