O2 SAT level

A normal O2 Sat is 98%. For most asthmatics, the O2 Sat does not drop except for during severe exacerbations. Some severe asthmatics may have a lower O2 Sat.

Where I work an acceptable O2 Sat is anything above 92 (+/- 2). If you notice your O2 sat drops significantly and stays there, then you should call your physician or go to the ER. You should also discuss with your doctor what your normal O2 sat is what to do if it drops.

That said, a pulse oximeter is not normally used as a monitor to help asthmatics decide what to do. Ideally, you should be acting before your O2 sat drops. However, I'm saying this not knowing how severe your asthma is.

You may already know this (but I have to say it), the asthma guidelines recommend every asthmatic work with his or her phsyician to create an asthma action plan to help you decide what to do when an attack is impending or ongoing. Some plans will have you utilize a peak flow meter, some will have you simply monitoring your symptoms, and some will have you using both methods. I describe this more fully in this post. Some asthmatics may incorporate other methods into the plan, such as the use of a pulse oximeter to monitor O2 Sats.

I provide more information on this topic here.