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Study's success leads to early halt of ventilator trial

BY: DOUG CAMPBELL

3/19/1999 - A large clinical trial of mechanical ventilator use for intensive care patients with Acute Respiratory Distress Syndrome (ARDS) is proving so successful that the study has been halted early.

The decision was made based on data from the study's first 800 patients, which showed a dramatic rise in survival rates among patients receiving small - rather than large - breaths of air from a mechanical ventilator.

ARDS is a devastating - and quite often fatal - inflammatory lung condition that usually occurs in conjunction with catastrophic medical conditions, such as pneumonia, shock, sepsis and trauma. Approximately 150,000 Americans are affected each year, and more than 40 percent of these people will die.

Scheduled to end later this year, the study was halted early so that critical care specialists could be alerted to the results, which showed approximately 25 percent fewer deaths associated with smaller-breath ventilation - findings that could end up saving as many as 15,000 lives per year.

Vanderbilt University Medical Center was one of 10 medical centers across the country participating in the ARDS Network Study of Ventilator Management, sponsored by the National Heart, Lung, and Blood Institute of the National Institutes of Health.

"This is a major first step in understanding the affects that ventilators have on these patients," said Dr. Gordon R. Bernard, professor of Medicine and the study's steering committee chairman.

It's also a therapeutic step that can be taken immediately, said Dr. Arthur P. Wheeler, associate professor of Medicine and principal investigator and publication committee chairman of the study.

"It costs nothing, it can be done on any ventilator and it can be done today. No study in ARDS in 25 years has made a difference in survival rates. This does," Wheeler said.

Previously, no specific therapies existed for ARDS patients. Treatment involves supportive care in an intensive care unit, including use of a mechanical ventilator and supplemental oxygen to help patients breathe.

"There are no medicines or therapies to reverse ARDS," Bernard said. "The treatment for it is entirely supportive, and the ventilator is the main item in that support. This study was the first to approach the question of ventilator managment, and its impacts on ARDS, in a standardized way."

The ARDS study, which began in 1996, compared the safety and efficacy of two different methods of setting ventilators. After informed consent was obtained, patients were randomly assigned to receive either relatively large or small breaths of air from the ventilator.

These ventilators deliver oxygen-enriched air to patients and allow removal of carbon-dioxide produced when patients exhale. Earlier studies had suggested that small breaths from a ventilator might not sufficiently remove carbon-dioxide and that large breaths might damage lung tissue, but several small clinical trials failed to show clearly which approach was superior.

"This trial was trying to answer what is basically a simple question - which type of breath, large or small, should be used for people with damaged lungs," Bernard said. "What we found is that ventilator's are not just passive devices."

The study coordinators stress that this new method is not intended for everyone on a ventilator, just ARDS patients.

The ARDS study was originally designed to enroll 1,000 patients, ages 18 and older. After 800, though, it was clear that the small-breath method was as safe and more effective than the large-breath method.

"Halting a large, multi-center clinical trial like this one is really a once-in-a-lifetime event for an investigator because it just doesn't often happen," Wheeler said. "It's really a testament to the method's effectivess. By reducing breath volume on ventilators for people with ARDS, in the very near future there could be 15,000 people walking around who before would have been dead."

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