Go through these in order and stop at the first one that applies. If you are reading this for someone else, answer for them.
Call emergency services for severe trouble breathing, chest pain, sudden weakness on one side, loss of consciousness, or another symptom that appears immediately life-threatening.
Do not drive yourself in an emergency.
Seek urgent medical advice if you have significant breathing difficulty, repeated fainting, or a rapidly worsening wound infection.
The article also says
Contact your healthcare team routinely if you develop a persistent rash, ear pain, wound redness or drainage, worsening pain, or unusual fatigue after treatment.
Also contact them if sessions repeatedly cause dizziness, breathlessness, or symptoms that interfere with normal activities.
Every sign above is quoted from the sofidex article on Hydrotherapy. If you are not sure, err upward — it is always reasonable to be checked.