Final answer:
The therapist should obtain an arterial blood gas to confirm the accuracy of the PetCO2 reading and assess the patient's acid-base status.
Step-by-step explanation:
The correct answer is C. obtain an arterial blood gas.
End-tidal CO2 (PetCO2) monitoring is a non-invasive way to estimate the partial pressure of carbon dioxide (pCO2) in the arterial blood. In this case, a PetCO2 of 59 torr suggests that the patient's arterial pCO2 may be elevated. To confirm the accuracy of the PetCO2 reading and determine the patient's overall acid-base status, it is important to obtain an arterial blood gas (ABG) measurement.
ABG analysis provides direct measurement of the patient's pCO2, pH, and other blood gas values. This can help the therapist assess the effectiveness of the current mechanical ventilator settings and determine whether any adjustments need to be made to optimize ventilation and acid-base balance.