What device is primarily used to measure end-tidal carbon dioxide (PETCO₂)?

The device primarily used to measure end-tidal carbon dioxide (PETCO₂) is a capnometer. This specialized instrument provides real-time data on the concentration of carbon dioxide in the exhaled breath at the end of expiration, which is crucial for assessing a patient's ventilatory status and metabolic function.

Capnometers work by utilizing infrared spectroscopy or other techniques to accurately measure the levels of CO₂ present in the exhaled air. The end-tidal CO₂ measurement is particularly important in various clinical scenarios, such as during sedation, in patients receiving mechanical ventilation, or in emergency settings, as it helps healthcare providers monitor the patient's respiratory adequacy and detect potential complications.

Other devices mentioned, such as a pulse oximeter, measure oxygen saturation levels in the blood, while spirometers assess lung function by measuring airflow and volume during inhalation and exhalation. Thermometers, on the other hand, measure body temperature and have no relevance to carbon dioxide measurement. Each of these devices serves a distinct purpose in respiratory care but does not measure PETCO₂ like a capnometer does.