"I have problems breathing when lying on my left side in bed. What can the cause be?" - Ted
Dr Sarah Jarvis says: "You're not giving me a lot to go on! Importantly, you don't say if this is a new or a long-standing problem. You also don't tell me if you're having pain or other symptoms when you lie on your left side.
Problems with breathing are common in all sorts of situations when you lie down. For instance, it's very common for coughing (and with it shortness of breath) to get worse when you lie down. In many cases this is because coughing is due to an upper airways or upper respiratory tract infection, also called an 'URTI'. When you're sitting or standing, the mucus produced in your nose trickles down the back of your throat and is swallowed. When you're lying, the mucus instead lands on the back of your soft palate, provoking a cough reflex.
There are many causes of shortness of breath or breathing difficulties. Any reduction in the usually highly efficient transfer of oxygen into the small airways of the lungs, and from there to the bloodstream, lowers the oxygen level in the blood. This in turn causes a reflex increase in breathlessness, which stimulates your body to breathe more often or more deeply to get more oxygen in. Asthma and chronic obstructive pulmonary disease (COPD) can both cause shortness of breath because of reduced oxygen transfer into the bloodstream. So too can panic attacks, which result in release of adrenaline into the circulation. This 'fight or flight' hormone stimulates increased breathing and a sensation of shortness of breath. Abnormal heart rhythms mean that blood circulation is less efficient, and the resulting lack of oxygen to vital organs causes shortness of breath. Heart failure, in which fluid can build up in the lungs and oxygen transfer is reduced, classically causes shortness of breath on lying flat.
But there are other causes of breathing problems not directly related to the heart or lungs. For instance, injury to the chest wall, including the intercostal muscles (the muscles between the ribs which expand every time you breathe in) can make it hard to breathe efficiently when they are compressed. In this case, lying in a particular position can make breathing harder.
If your breathing difficulty is severe or persistent, I suggest you see your doctor to get an examination of your heart, lungs and chest wall in order to get a better idea of what the problem could be."