New ventilation system can reduce deaths from acute respiratory distress syndrome

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New ventilation system can reduce deaths from acute respiratory distress syndrome

New York Scott Gottlieb

Patients who are critically ill with the serious lung condition known as acute respiratory distress syndrome sometimes die because organs other than their lungs begin to fail. The condition is then called multiple organ dysfunction syndrome.

Acute respiratory distress syndrome, which can result from pneumonia, trauma, sepsis, or other factors that cause injury to the lungs, typically triggers widespread inflammation and the build up of fluid in the lungs. About a third of patients who develop the condition die, but more than 60% of patients who go on to develop multiple organ dysfunction syndrome die.

In the past few years doctors have found that a new method of mechanical ventilation—recommended for use on patients who have developed acute respiratory distress syndrome in order to avoid additional lung injury—can make a substantial difference to patients’ survival.

This newer "lung protective" ventilation strategy, in which tidal volumes are smaller, has also been shown to help reduce multiple organ dysfunction syndrome, although the reason until now has been unclear.

In the new strategy the ventilator is set to administer smaller breaths of air than the conventional method and to keep the lungs more inflated at the end of each breath, said Dr Arthur Slutsky, an author of the new study and a professor of medicine and surgery at the University of Toronto (JAMA 2003;289:2104-12).

The report helps to explain why the protective strategy saves more lives than the conventional approach.

In the first of two experiments the investigators used an animal model of acute respiratory distress syndrome to show that the conventional approach to mechanical ventilation accelerated cell death in the kidneys and small intestines of rabbits. The conventional approach was also associated with greater levels of biochemical markers indicating kidney dysfunction than the new strategy. The researchers then observed that rabbit kidney cells in a laboratory dish died more quickly when exposed to blood taken from rabbits that had been ventilated under the conventional approach. They also found that blocking a particular protein, called soluble Fas ligand, helped delay cell death. Past research has already implicated this protein in promoting cell death.

The investigators then compared blood samples from 11 people with acute respiratory distress syndrome who had been ventilated with the conventional approach with samples from nine patients who had lung protective ventilation.

Results showed that levels of soluble Fas ligand were higher in patients ventilated under the conventional approach. The higher levels of the protein were linked to increases in creatinine, a sign of kidney dysfunction. As such, circulating levels of soluble Fas ligand may be involved in promoting multiple organ dysfunction syndrome in patients on conventional ventilation, the researchers conclude.

The findings may help researchers develop new ways of combating multiple organ dysfunction syndrome, which currently has no treatment, according to the authors. The results confirm previous research showing that the newer ventilation strategy is optimal and that the technique should become standard at more hospitals, the researchers noted.

"These findings offer more evidence for why doctors should be using it," Dr Slutsky said. "This can be done with virtually any ventilator," he said. "It’s pretty straightforward."

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