Jill, a 26-year-old gymnastics instructor, presents with complaints of muscle weakness in her face that comes and goes,

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Jill, a 26-year-old gymnastics instructor, presents with
complaints of muscle weakness in her face that comes and goes, but
has been getting worse over the past two months. Most notably, she
complains that her "jaw gets tired" as she chews and that
swallowing has become difficult. She also notes diplopia ("double
vision") which seems to come on late in the evening, particularly
after reading for a few minutes. At work, it has become
increasingly difficult to "spot" her gymnasts during acrobatic
moves because of upper arm weakness.
On physical examination, she has notable ptosis
("drooping") of both eyelids after repeated blinking exercises.
When smiling, she appears to be snarling. Electromyographic (EMG)
testing revealed progressive weakness and decreased amplitude of
contraction of the distal arm muscles upon repeated mild shocks (5
shocks per second) of the ulnar and median nerves. Both her
symptoms and electromyographic (EMG) findings were reversed within
40 seconds of intravenous administration of edrophonium (Tensilon),
an acetylcholinesterase inhibitor. Blood testing revealed high
levels of an anti-acetylcholine receptor antibody in her plasma,
and a diagnosis of myasthenia gravis was made.
Jill was treated with pyridostigmine bromide, which is a
long-acting anticholinesterase drug, and was also started on
prednisone, which is a corticosteroid drug. She was given a
prescription of atropine as needed to reduce the nausea, abdominal
cramps, diarrhea, and excessive salivation she experienced as side
effects of the anticholinesterase drug.
5. Jill's doctor advises her that she is at increased
risk for respiratory failure. Why?
4. How will the corticosteroid prednisone benefit this
patient?