Final answer:
The nurse should monitor the client's capnography levels to determine if they are ready for discharge after the outpatient endoscopy procedure.
Step-by-step explanation:
The nurse should monitor for the client's capnography to return to baseline as an indication that the client is ready for discharge.
Capnography measures the level of carbon dioxide in the exhaled breath, and a return to baseline levels indicates that the client's respiratory function has returned to normal after the endoscopy procedure.
Monitoring for the client's ability to respond when called, passing flatus, and requesting oral intake are also important assessments, but they may not specifically indicate readiness for discharge.