Final answer:
After a brain stem infarction, a nurse should observe for bradypnea, as the respiratory centers are located in the brain stem and can be affected by the stroke.
Step-by-step explanation:
After a patient experiences a brain stem infarction, the nurse should observe for bradypnea. A brain stem infarction, which is a type of stroke, can cause various neurological impairments depending on the specific area of the brain stem that is affected. The respiratory centers are located in the brain stem, and hence, infarction in this area could lead to bradypnea, which is abnormally slow breathing rates. Symptoms such as aphasia, contralateral hemiplegia, and numbness and tingling to the face or arm may suggest infarctions in other parts of the brain, but bradypnea is more specific to the brain stem region.