Go through these in order and stop at the first one that applies. If you are reading this for someone else, answer for them.
1
Is any of this happening now?
Call 911
Seek emergency medical help for:
Severe or rapidly worsening breathlessness, especially at rest
Fainting or near-fainting
New or severe chest pain
Blue or grey lips, confusion, or extreme drowsiness
Coughing up more than a small streak of blood
Sudden symptoms suggesting a problem with continuous intravenous treatment
Other emergency signs, for anyone
Someone who is struggling to breathe, gasping, choking, or cannot get words out
Someone who has chest pain, tightness or pressure lasting more than a few minutes
Someone who has sudden weakness or drooping on one side of the face or body, slurred speech, or sudden confusion
Someone who is unconscious, or cannot be woken
Someone who is bleeding heavily and it will not stop with firm pressure
Someone who has had a seizure that will not stop, or does not wake up afterwards
Someone who has lips or skin that look pale, blue, grey or blotchy
Someone who you believe has taken an overdose or swallowed something poisonous
2
Is any of this happening?
Be seen today
Arrange a routine or prompt review if you notice a gradual increase in breathlessness, reduced ability to do normal activities, new ankle swelling, abdominal swelling, rapid weight gain from fluid, or more frequent palpitations.
These changes may mean that treatment or fluid management needs reassessment.
Contact the specialist team promptly if medicine side effects are difficult to manage, doses have been missed, or there is a problem with a pump or continuous infusion system.
Abrupt interruption of some continuously delivered PAH medicines can be dangerous.
The article also says
Do not drive yourself if you are faint, severely breathless, or having significant chest pain.
Every sign above is quoted from the sofidex article on Primary pulmonary hypertension. If you are not sure, err upward — it is always reasonable to be checked.