25/09/2026
Breathless when you lie flat or bend down to tie your shoes? A paralysed diaphragm could be the reason.
The diaphragm is your main breathing muscle, a dome that sits under the lungs and separates your chest from your abdomen. Each half has its own nerve, the phrenic nerve, which runs from the neck down through the chest.
When that nerve is injured, one side of the diaphragm stops working properly. It can happen after heart or chest surgery, after a virus or an accident, or because something in the chest is pressing on the nerve, which we always check for. In a large number of people, we never find a cause.
Often the first clue is a routine chest X-ray showing one side of the diaphragm sitting much higher than the other, usually reported as a raised or elevated hemidiaphragm. To confirm it is paralysed and not just raised, I use a sniff test, an ultrasound, and breathing tests done sitting up and lying flat. Those results tell me how much treatment is likely to help.
[DISCLAIMER: suggest a short line that this is general information, not personal medical advice]
Save this if you or someone you know has been told their diaphragm is raised. Part two, on treatment, is up next.