The treatment we are studying is Transcranial Magnetic Stimulation (TMS). In TMS, an electromagnetic pulse is passed into the brain through a coil placed on the head. Previous studies have shown TMS to be capable of altering brain activity in specific areas; for example it has been used to improve mood in clinical depression. In this study we will assess if, by targeting TMS to the brain area responsible for feeling breathless, participants' breathlessness will be improved