Which situation might require the recalibration of a capnometer?

Recalibrating a capnometer is essential for ensuring accurate measurements of carbon dioxide levels in exhaled air. Consistent high PETCO₂ (end-tidal carbon dioxide) readings indicate that the device may not be providing accurate results. This scenario suggests a potential calibration issue, as normal physiological values for PETCO₂ typically range between 35 and 45 mmHg in healthy individuals. When readings consistently exceed this range, it could point to a malfunction or that the device is not correctly measuring exhaled CO₂ levels, necessitating recalibration to restore accuracy and reliability in monitoring the patient's respiratory status.

High readings might also suggest external factors or malfunctions that have interfered with accurate readings, but without recalibration, it would be difficult to determine the true status of the patient's ventilation, which is critical in clinical decision-making. Therefore, recalibration in this context is a necessary step to maintain the integrity of respiratory monitoring.

In contrast, other options describe situations such as phase 1 returning to zero, which is a normal phase in capnography and does not require recalibration. Similarly, normal fluctuations in PETCO₂ or the scaling of phase 3 also fall within expected parameters and do not indicate a necessity for recalibration.