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If you have heart failure, you may have a hard time lying flat on your bed or using only a moderate-sized pillow. You may use a few extra pillows. Some people with severe heart failure that is not properly treated sleep sitting up in a chair.

If you have heart failure and you find that you cannot breathe comfortably lying flat or on a moderate-sized pillow in bed, tell your doctor right away.

If the left side of your heart doesn't pump as well as it should, blood can stay in the upper left chamber (the left atrium) instead of being pumped out around your body. Because blood sits in this chamber, pressure builds up in the blood vessels behind it. The extra pressure causes fluid to leak from blood vessels into your lungs. This causes shortness of breath.

If you are having trouble lying flat in bed, it means you have fluid in your lungs. When you lie down, gravity makes the fluid pool there. This makes it harder to breathe.

To learn more, see What is heart failure?

This information is for educational use only, and is not a substitute for prompt professional medical advice. Readers should always consult a physician or other professional for advice and treatment. ©BMJ Publishing Group Limited 2008. All rights reserved.