To add on to that, get to know what your child's breathing looks like when NOT having an attack. Otherwise it can be hard to know what you're looking at.

If your child has cough-variant asthma, though, you may not see this. O2 levels may also be fine. DD has CVA, and hers always were. However, her symptoms were extremely disruptive and incessant. DS wheezes and has low o2, but actually suffers less, because he responds to albuterol (she didn't) and doesn't cough all night.