Taxol side effect

My mom has been receiving Taxol over the last 4 months and has pretty much evey side effect there is but the one that is debilitating is shortness of breath.  Her doctor seems to think that there may be another problem not related to the cancer or cancer treatment that is causing this to happen.  Her blood is normal and her lungs are clear in fact the catscan showed that her chest and lungs were normal.  If it isn't the Taxol causing this what could it possibly be?

[Cleveland Clinic]

Dear Kab42820, Over the internet without ability to evaluate including medical history and physical examination it is difficult to pinpoint the cause of your mother's symptoms.  Shortness of breath is a very uncommon side effect of taxol, and severity of which is not reported, and could be related to other conditions or problems.