I am NOT an expert, but I can relate my husband's experience and also caution you to be sure you are seeing a CML specialist (not just a community onc) familiar with all the medications and dose optimization. My husband (age 74) did well on Tasigna and was at 300 or 400 mg per day (don't recall which, it had been lowered from the original starting dose) and undetectable when he first tried TFR. When he failed TFR his onc (CML specialist) put him on Sprycel, starting 70 mg, because my husband had what might have been an occlusive event and the oncologist was very concerned about the cardiovascular implications of Tasigna. Sprycel brought him right down to undetectable and after a short drug holiday for SOB reduced to 50 mg Sprycel. The SOB returned (much worse) and after a 4 month drug holiday (turning into TFR attempt by default) his PCR just creeped up to .026 so a return to meds is likely in his near future. After considerable discussion he is likely going on low dose of Bosulif when he reaches .1. Gleevec was another consideration, but he has some other medical issues (eye and GI) that the onc felt Gleevec was not his best choice.
As for the pulmonary issues on Sprycel, he has dealt with a pulmonologist and cardiologist and all have ruled out PE or PAH. It's a mystery why some get SOB from Sprycel for no apparent reason.
While this does NOT answer your question, thought that hearing about his journey may give you some info. Good luck and hope the next medication works well and doesn't cause side effects. Good to hear they are starting you on a lower dose -- your original post indicated a much higher dose, but you've indicated a lower dose further down in the thread. From our experience, and from reading about others on the boards, many people do well on lower doses.