Yes, the regular ("normal") saline concentration in our blood and tissues is usually .9% - of course it can vary slightly among individuals and with some meds and conditions.
When they give you an IV in the hospital, it is most usually .9% saline. They may use it for hydration, add other nutrients, or use it to push IV meds.

I forgot to explain why the hypertonic helps.
Saline in just salt (sodium chloride) water. As Sue said, the .9 is the same concentration as in our body (isotonic). The higher amounts of salt draw more water from body into airways, thinning the mucus and making it easier to cough out.