The elderly patient receiving a continuous morphine infusion for the treatment of cancer pain is at risk for opioid-induced respiratory depression. The nurse selects which monitoring device to most quickly detect a change in the patient’s respiratory drive?

End-tidal carbon dioxide. End-tidal carbon dioxide (ETCO2) monitoring will detect deterioration in the patient’s respiratory status more quickly than pulse oximetry because the patient will maintain oxygenation longer than he or she will be able to blow off CO2. Therefore, the ETCO2 will demonstrate retention of CO2 earlier than the pulse oximeter will demonstrate desaturation. Telemetry and noninvasive blood pressure would only provide very late signs of decompensation in the patient.