Asthma when is a nebuliser actually needed?

[AvocadoAndFitch]

DD2 has asthma and a possible immune disorder amongst her other problems. She has constant infections so, is on antibiotics practically weekly and everytime I take her to the GPs they nebuliser her before checking her chest as they can't hear otherwise. Also if I go in saying I think she needs one they do.

But when do they nebulise normally. Does it go on difficulty breathing, noise, colour or if inhalers don't work?

DS (2.5) is asthmatic and tends to be nebulised when 10 puffs of ventolin don't work. For him it goes off all of the things you mentioned plus his sats.