You're all set for a good night's sleep. You lie down, get comfortable, and soon you are far away in dreamland. But, after a couple hours, you suddenly wake up, feeling like you are being suffocated. You sit up to try and breathe and after a few minutes you start to feel better. This condition is known as paroxysmal nocturnal dyspnea and is a sign of heart failure or a heart condition.

When you lie down, as a result of gravity, the fluid in your body redistributes, so that there is less fluid in the legs and more fluid in the lungs. If your heart is functioning normally, this shouldn't be a problem. However, if you have a heart problem, your heart may not be able to cope with the extra load placed on it when you lie down. The additional volume of blood in the blood vessels of lungs creates a lot of pressure and pushes fluid through the walls of the blood vessels and into the lung tissue. This fluid clogs up the alveoli, or tiny air sacs, in the lungs, preventing oxygen transfer from taking place. Therefore, you suddenly wake up feeling like you are suffocating, which essentially is true. These symptoms are relieved by sitting up, since gravity helps the heart to pump the fluid out of the lungs.

Some other symptoms that you may experience with paroxysmal nocturnal dyspnea, which also indicate congestive heart failure, are swollen ankles, exercise intolerance, rapid weight gain, excessive sweating and an irregular heartbeat. Heart failure is usually treated using a variety of medications and by adopting lifestyle changes, such as a healthy, salt-free diet, reducing alcohol intake, quitting smoking and doing light exercise on a regular basis. You may also need to be on a fluid restriction, since reducing the volume of fluid circulating through your body reduces the workload of your heart.