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
ventilationrecommended for use on patients who have developed acute respiratory
distress syndrome in order to avoid additional lung injurycan 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. "Its
pretty straightforward."
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