People with heart failure may experience breathlessness when resting or lying down. The feeling that you cannot breathe may come on suddenly and can even wake you from your sleep.
You may feel more breathless lying down because the fluid in your lungs (congestion) moves with gravity, making more of your lungs wet (think of liquid in a bottle upright and then lying on its side).
You can ease your breathing in this case by using extra pillows to prop you up. If this is happening consistently, or you need more pillows, your heart failure may be getting worse. Awakening due to shortness of breath is serious. You should consult your doctor or nurse. Adjustments in your treatment may be necessary.