What Causes Heavy Breathing?

Hello, my grandmother 77yr old, had a stroke 20months ago, can not talk lost movement on her right side can not swallow ect, she has been hav'n seizures quite regularly,, today she had 2, 3 hours apart,, the nurse's at the nurseing home put her to bed n tried settle'n her to rest,, but as we think she has settle'd,, she will start breathing heavy, seem's to be really anxious,, (lasts about 2minute's) settle's then breaths heavy again,, this is ongoing could u suggest reason's or any suggestions on proventing this??? would be much appreciated....