WATCH: Sonia O'Sullivan joins pulmonary hypertension campaigners

Campaigners, including Sonia O'Sullivan, are raising awareness for pulmonary hypertension.

Pulmonary hypertension is a lung condition in which there is increased pressure in the pulmonary arteries that travel from the heart to the lungs.

"Pulmonary hypertension is a very rare disease. There are only about 300 patients in Ireland with PH. We are constantly trying to make people aware of it because often it can be mistaken for a less serious illness," explained Regina Prenderville from the Pulmonary Hypertension Association.