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September 26, 2001

Heavy Breathing in the Night:
Central Sleep Apnea in Heart Failure

Penn Researchers to Lead Study on Sleep Apnea's Effects on Heart Physiology

(Philadelphia, PA) - Many people feel beat without a good night's sleep, but for some folks, it may be their heart that's taking a beating. Researchers at the University of Pennsylvania Medical Center are leading a comprehensive multi-center clinical trial in the treatment of central sleep apnea and exploring 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 it is also the examination of heart physiology during episodes of sleep apnea.

"In this study, we are looking how to treat CHF patients with a unique CPAP device designed to automatically respond to their breathing patterns," Lee Goldberg, MD, MPH, assistant professor of medicine in the Penn Heart Failure and Cardiac Transplant Program. "Since heart failure patients often develop central sleep apnea, we also want to learn more about the physiology of the disorder and how it can exacerbate their condition "

The term congestive heart failure describes the state of a person with a weakened heart - whether it is due to age, a heart attack, coronary disease, or a number of other conditions. As a result, the heart is not strong enough to pump enough blood throughout the body, leading to shortness of breath and fatigue. Sufferers also retain fluids in their limbs due to the lack of blood flow, hence the term 'congestive.' It is the decreased blood flow, in fact, that can lead to developing central sleep apnea.

There are two forms of sleep apnea, obstructive and central. Just as it sounds, obstructive sleep apnea is caused when the muscles of the throat relax, obstructing the airway. Central sleep apnea, however, is caused as chemical sensors in the brain confuse a rise in carbon dioxide in the blood (due to low blood volume) with hyperventilation. In response, the brain sends a signal to the lungs, which tells them to slow breathing.

"This often jolts the patient awake, ruining a good night's sleep and delivering a shot of adrenaline to an already-weakened heart," explained Goldberg. "The lack of sleep also makes simple tasks difficult - balancing a checkbook suddenly becomes more difficult than plotting a moon landing."

One of the most useful treatments of central sleep apnea involves CPAP systems, which deliver air through a small mask that covers the nose. The constant pressure keeps the airway open, which prevents both snoring and episodes of apnea. ResMed Inc.'s AutoSetÓ CS, which the researchers are studying in this trial, is different from similar devices in that it monitors the patient's breathing on a breath-by-breath basis and automatically adjusts the pressure as required. Therefore, the user receives the minimum amount of pressure they need for effective therapy.

"Since CPAPs must stay on all night, patients find them to be uncomfortable - like heavy breath being blown into their face all night - and find reasons not to use CPAP therapy," said Allan Pack, MD, PhD co-lead investigator and director of Penn's Center for Sleep and Respiratory Neurobiology. "According to the manufacturers, the advantage of the AutoSet CS device is that it only turns on when you need it, which we hope will lead to better compliance with the therapy."

Pack and Goldberg are looking to enlist 200 CHF patients nationwide, coordinating efforts with colleagues at five other locations throughout the United States. While they can use the CPAP at home, the patients would be required to spend the night at the Center for Sleep and Respiratory Neurobiology on four separate occasions throughout the study. In addition to receiving the treatment at no cost, patients will also be compensated for travel expenses.

Volunteers or referring physicians can call (215) 615-0800 to receive more information.

Funding for this study is provided by the National Institutes on Health and ResMed, Inc.

"Speaking as a cardiologist, we find this type of work especially rewarding," said Goldberg. "Not only do we have a way to easily increase a patient's quality of life, but we also get to delve into a new way of looking at the physiology of the heart and its relationship with the other organs."

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Editor's Note: Neither Dr. Pack nor Dr. Goldberg have any financial interest in ResMed, Inc.






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