Obstructive Sleep Apnea: A Sleeping Threat for People with Heart Failure
Find out why this common sleeping disorder is especially dangerous for patients with heart failure.
Obstructive sleep apnea (OSA) is a common but often overlooked sleep disorder characterized by frequent, extended pauses in breathing (“apneas”) during sleep. In addition to depriving suffers of a refreshing night’s rest, OSA is linked to a host of chronic conditions, among them heart failure. In a December 2010 article in the Journal of the American College of Cardiology, researchers attempted to pinpoint the physiological factors that connect these two conditions with an eye toward therapies that could improve both.
During sleep, throat muscles naturally relax and airways get narrower. In patients with obesity, where sleep apnea is common, person’s air passages are smaller than usual due to fat in the throat. When sleeping, the loss of muscle tone can lead to the throat passages narrowing even further leading to periods where no breathing (apnea) or very reduced breathing occurs. During these periods, the body’s oxygen supply is almost completely cut off. The apnea episodes can last from 10 seconds to a minute or more, and generally occur between 5 and 30 times an hour.
Sleep is normally a time when the cardiovascular system rests with lower heart rates and blood pressure, but the repeated withdrawal of oxygen during apneas causes surges in blood pressure and diminishes the heart’s ability to fill and pump effectively. The repeated bouts of low blood oxygen have also been linked to damage in the arteries and irregular heart rhythms.
Due to these factors, heart failure patients with OSA are 3 times more likely to die from a heart attack or other cardiac event than their counterparts who sleep normally. Conversely, when heart failure patients with OSA were treated with a technique called continuous positive airway pressure (CPAP) that keeps air passages open during sleep, their blood pressure and heart rate dropped, and the stress on the heart subsided.
To test the hypothesis of a two-way connection between heart failure and OSA, scientists performed experiments on healthy volunteers that mimicked the patterns of excess fluid retention common in people with heart failure. The research demonstrated that the extra fluid that settles in the lower extremities when an individual is standing or sitting during the day, will migrate upward to the neck veins when the person reclines at night. This in turn causes swelling that constricts the air passages and sets the stage for OSA. However, no studies have yet to confirm that treating fluid retention in heart failure can improve OSA symptoms.
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