Researchers Study
Apnea and Heart Failure
May / June 2002
Researchers at the Hospital of the University of Pennsylvania
are leading a comprehensive, multi-center
clinical
trial
in
the treatment of sleep apnea and its relationship with congestive
heart failure (CHF). The trial is not only a test of an
innovative
new continuous positive airway pressure (CPAP) device, but
also is the examination of heart physiology during episodes
of sleep apnea.
Initially, pilot studies in Europe and the United States
were developed to study fatigue in CHF patients. Surprisingly,
researchers found that CPAP not only greatly improved the
patients' fatigue, but also reduced their shortness of breath,
improved their ability to walk a further distance and enabled
them to be more active.
"We are studying the physiology of central sleep apnea
in patients with CHF, the heart failure outcomes related
to
this disorder and the efficacy of this particular device
to treat the disorder," says Lee
Goldberg, MD, MPH, cardiologist in the Penn
Heart Failure and Cardiac Transplant Program.
The ResMed Inc.'s AutoSet CS, which is being studied in this
trial, has the ability to self-titrate (adjust its pressure
as needed), a major technological breakthrough in CPAP therapy.
The machine monitors the patient's breathing pattern, detects
periods of rapid breathing and pauses in breathing, and adjusts
the pressure to the minimum amount to maintain even breathing.
"The new device essentially senses breathing and adjusts
its response to the patient's breathing accordingly. It is
much more comfortable than a static device where the pressure
is constant, regardless of whether or not the patient is awake
or breathing irregularly," explains Dr. Goldberg.
"Because CPAPs must stay on all night, patients find
them to be uncomfortable and find reasons not to use CPAP
therapy," says Allan Pack, MD, PhD, co-lead investigator
and director of the Penn Center for Sleep and Neurobiology.
"This new technology should lead to better compliance
with the therapy."
There are two kinds of sleep apnea-the more common obstructive
sleep apnea (usually in people who are obese) and central
sleep apnea. Central sleep apnea, the focus of this clinical
trial, occurs when there is a disconnection between the brain
and the respiratory control center in monitoring the amount
of oxygen and carbon dioxide in the blood.
"We think this disconnection is caused by the fact that
there is a slow cardiac output and therefore the thermostat
is not getting accurate signals," explains Dr. Goldberg.
Furthermore, when someone has central sleep apnea, their body
experiences arousals-sudden bursts of high doses of stress
hormones like adrenaline-that overstimulate the heart. Over
time, these arousals cause the heart to work less efficiently,
which can lead to the progression of heart failure.
For patients, the benefits can be many. "This is a non-drug
therapy that has the potential to eliminate patients' apnea
and have a positive physiological effect on their heart failure,"
says Dr. Goldberg.
"In the next six to 12 months we expect to embark upon
a comprehensive research program that may include three or
four clinical trials looking at various aspects of the impact
of sleep on the heart," adds Dr. Goldberg.
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