Annie, I know about this type of morphine but morphine is morphine is morphine! Chime in here any time, Mrs. D.
http://www.drugs.com/mtm/roxanol.html
I have known people who have had it. It still affects breathing. I hope they will think about the dose amount or other alternatives. I don't mean to add to your stress but unless they think your Mom's time is near and they are trying to make her comfortable, they could make things much worse.
I know how hard this is. My Grandma and my Dad went through years of health issues. It can be very overwhelming. Faith helps, as does knowing that you love your Mom and she knows it.
Annie