How Sleep Apnea Affects The Cardiovascular System

Original article printed in Heart Insight magazine, August 2007

Imagine waking up choking and gasping for air, then catching your breath and falling back into fitful slumber — for a minute or two, until it happens again. And again. And again. Five to 30 times a night.

That's what it's like to have sleep apnea, a potentially life-threatening sleep disorder in which tissues in the throat collapse and block the airway. Ever vigilant, the brain forces the sleeper awake enough to cough or gulp air and open the trachea up again. But then, the whole cycle starts all over again.

Pauses in breathing can contribute to severe fatigue during the day, increase your safety risks, and make it difficult to perform tasks that require alertness. "You could crash your car, or get hurt at work," says Nidhi S. Undevia, M.D., medical director of the Center for Sleep Disorders, Loyola University Health System, Maywood, Ill.

 Sleep apnea is also a risk factor for such medical problems as high blood pressure, heart failure, diabetes and stroke, she adds.

Three Types

Some 12 million Americans have sleep apnea, according to National Heart, Lung, and Blood Institute estimates. There are three types: obstructive sleep apnea (OSA), central sleep apnea (CSA) and mixed apnea, which is a combination of the other two types.

The most common is OSA, obstructive sleep apnea. The typical OSA patient is a man over the age of 40 who is overweight and has a thick neck measurement. He typically can't button the top of his shirt collar unless it measures 17 inches or larger. However, OSA can affect women and children as well. Anyone who is overweight, suffers chronic nasal congestion, or has large tonsils or other structural abnormalities blocking the airway has an increased risk.

Up to half of people who have OSA also have high blood pressure and — unlike most people — their blood pressure does not fall while they're asleep.

"Doctors don't know whether sleep apnea elevates blood pressure because of repeated awakenings or because of drops in oxygen levels [in the blood]. It's likely to be a combination of both," says Daniel Norman, M.D., fellow in Pulmonary and Critical Care at the University of California San Diego Medical Center.

"OSA also stresses the heart," says Shahrokh Javaheri, M.D., Emeritus Professor of Medicine at the University of Cincinnati College of Medicine and medical director of Sleepcare Diagnostics in Mason, Ohio. "Lack of oxygen and rising blood pressure both contribute to OSA-related heart failure," he adds.

"With CSA [central sleep apnea], airway blockage isn't the problem. It's that the brain doesn't send regular, continuous signals to the muscles of the diaphragm to contract and expand [and the pattern for inhaling and exhaling is disrupted during sleep]. Central sleep apnea may develop after a stroke, or may be caused by sedatives, narcotics and brain injury," explains Undevia. Heart failure patients are susceptible to developing a type of CSA called Cheyne-Stokes respiration.

Keeping blood-oxygen levels normal during sleep may lessen the severity of CSA in these patients. In a pilot study with 12 CSA patients who had heart failure, Javaheri found that a dose of acetazolamide–a mild diuretic and respiratory stimulant–one hour before bedtime reduced the number of episodes of interrupted breathing while also improving blood oxygen levels. The patients, who were given the drug over a six-day period, also felt better rested and less sleepy during the daytime. This was only a six-day study, though, says Javaheri, and more research is needed to determine whether long-term use will improve heart function as well.

Diagnosis and Treatment

If you always feel sleepy despite being in bed eight hours a night, or your spouse delicately suggests separate bedrooms because your snoring has become unbearable, you should ask your doctor about sleep apnea. You will most likely be referred to a sleep disorders specialist, and will need to spend a night or two in a lab hooked up to a machine that will monitor and chart your brain waves, oxygen levels, breathing and heart rate while you sleep.

Looking at the brain wave pattern tells us whether or not you are fully asleep, and charts the quality of your sleep. We also look for pauses in breathing, and whether you wake up during those pauses, says Undevia. During breathing pauses, oxygen levels are checked, and we measure whether heart rate slows or becomes irregular. Generally, five pauses in breathing an hour may be a mild case [of apnea], and 30 or more may be a severe case.

If the test shows that you have sleep apnea, there are certain lifestyle changes that might be recommended, and you will most likely be fitted for a continuous positive airway pressure (CPAP) mask to wear while you sleep.

How a CPAP can help: An air compressor in the CPAP device helps deliver a steady stream of oxygen while you sleep. As you inhale, it creates enough added pressure to produce a steady stream of air that keeps your airways open.

With continuous oxygen and regular breathing, you sleep better and feel more rested. As an added bonus, elevated blood pressure drops significantly after using the mask for two weeks, according to a study of 46 OSA patients conducted by Norman. In his study, patients in the first group used a pressurized CPAP oxygen mask, the second group used a placebo mask with reduced pressure and the third group wore a mask delivering supplemental oxygen without the added pressure to keep the airways open. In this study, the positive pressure — and not the oxygen — had a beneficial effect on blood pressure. So you may experience multiple benefits from using a CPAP to treat this condition.

Although the mask is effective, some patients complain of claustrophobia and discomfort, or simply having trouble falling asleep while wearing it. Trying a mask with a different style or a different fit may solve this problem.

But when someone with a case of sleep apnea is unable to use the mask, there are also surgical alternatives. For instance, the Pillar procedure is a minimally invasive technique that involves inserting three rods, each 3/4 inch long, into the roof of the mouth. Scar tissue forms around the implants, which firms and supports the roof of the mouth to prevent its collapse during sleep.

Surgical procedures can make the back of the throat larger or tissues in the nose smaller. Using a thin, lighted scope snaked up your nose, an ear, nose and throat (ENT) surgeon will see where the blockage is, says Undevia, and then may recommend having your tonsils removed or correcting a deviated septum in the nose.

Other surgical options include making the roof of the mouth smaller or removing part or all of the uvula (the tissue that hangs from the roof of your mouth in between your tonsils).

Doctors used to alleviate sleep apnea by performing a tracheostomy — cutting a hole in the windpipe — which is still an option in severe cases when CPAP does not work.

Sleep apnea isn't just snoring. Left untreated, the condition can lead to serious cardiovascular problems. Fortunately, there are several non-surgical and surgical treatment options you can discuss with your doctor. Your rest is important for many reasons. We hope you'll soon be enjoying the benefits of a good night's sleep!