A Glimmer of Hope for a Brutal Condition

cute respiratory distress syndrome—called ARDS—isn’t easy to define. The brutal malady is actually caused by several different conditions, including pneumonia and other infections like peritonitis, and also by severe trauma. It is marked by an abnormal accumulation of fluid or inflammatory tissue in the lungs. Muscles for breathing are forced to work harder, and there is poor gas exchange in the lungs and low levels of oxygen in the blood.

“Ordinarily,” explains Hopkins pulmonologist Roy Brower, M.D., “you might breathe 12 to 14 times a minute. But when the lungs become inefficient you have to breathe 30 times a minute. You look like you just ran around the block.”

Sadly, over the years there hasn’t been much headway against ARDS. Of the approximately 150,000 Americans the condition affects annually, more than 40 percent die. In 1996, to try to lower those numbers, a consortium of 10 medical centers funded by the National Heart, Lung and Blood Institute, known as the ARDS network, began testing new kinds of treatment. Early this year, one of these methods—a more conservative application of the mechanical ventilator—delivered pay dirt.

With no specific therapies in hand, doctors have typically used the mechanical ventilator in an intensive-care unit to help ARDS patients breathe. But physicians have long known that as the ventilator delivers its breaths of oxygen-enriched air to the body, a generous tidal volume, which is effective at getting oxygen in and carbon dioxide out, is also hard on the lungs. “Our thinking was that we might get a better outcome if we used a small tidal volume,” explains Brower, who led the national study. “By being gentler, we’d give acutely inflamed and injured lungs a better chance of healing from the process that started ARDS in the first place.”

Earlier studies, though, had suggested that small breaths might not remove sufficient carbon dioxide, and several limited clinical trials had failed to show clearly which way of setting the ventilator was more effective. This time, pulmonary specialists set out to compare the two methods and demonstrate that by lowering tidal volume, further injury to the lungs by the ventilator itself could be minimized. Slated to run until the end of 1999, the study was designed to enroll 1,000 informed ARDS patients, 18 years and older, and randomly divide them into two treatment groups. Those in the first group received relatively large breaths of air; patients in the second group received smaller breaths.

By March 10 of this year, nine months ahead of schedule, the numbers were in. Of the first 800 patients studied, a remarkable 25 percent fewer deaths had occurred among those receiving smaller breaths. The definitive evidence should save thousands of lives each year. In a press release to medical centers around the country, the National Heart, Lung and Blood Institute of the National Institutes of Health recommended the study be stopped immediately so critical-care specialists could be alerted to the results and patients could begin benefiting from the data.

The results are especially gratifying, according to Brower, because ICUs, with their diverse patient populations, are difficult places to carry out studies. “As best we can tell,” he says, “this is the first multicenter trial that’s going to have a definitive effect on how physicians manage the ventilator for this condition. Patients will be able to leave the ventilator sooner, and the mortality rate from ARDS is going to drop.”

-- Gary Logan