What must be performed and stored as part of the patient's record to document the calibration of the equipment?

The correct choice appropriately emphasizes the importance of documenting the proper functioning of patient sensors as part of the calibration process for sleep study equipment. This documentation is crucial because it provides evidence that the sensors, which are integral to obtaining accurate readings during polysomnography, are working correctly. If sensors are faulty, it could lead to misleading results in the patient's sleep study assessment, affecting diagnosis and treatment plans.

When calibrating equipment, ensuring that patient sensors are functioning properly is paramount. This includes not only verifying that the sensors are connected correctly but also confirming that they provide reliable and valid measurements. Should any malfunctioning sensors go unrecorded, it could lead to significant gaps in the patient's record, compromising the clinical outcomes.

While other options mentioned, such as the integrity of electrode wires or impedance readings, are important aspects of preparing equipment, they serve as checks rather than being direct indicators of the patient sensors’ performance. Documenting the functioning of patient sensors ultimately provides a comprehensive overview of the equipment's readiness and reliability in capturing the necessary data during the sleep study.