On an ECG machine, the sensitivity switch controls what aspect?

The sensitivity switch on an ECG machine is responsible for controlling the amplitude and gain of the electrical signals that are recorded. By adjusting the sensitivity, you change how much the machine amplifies the electrical signals from the heart. This is crucial because it influences the height of the deflections on the ECG tracing. Increasing the sensitivity means that smaller electrical signals can be displayed more prominently, making it easier to identify abnormalities in the heart's rhythm and overall health. Conversely, decreasing the sensitivity may be used when the signals are too large, allowing the clinician to get a clearer view of the data without it being overly distorted.

Other options focus on different functionalities; for instance, heart rate relates to the frequency of the rhythm, lead placement is about where the electrodes are positioned on the body, and paper speed determines how quickly the ECG results are printed out, but none of these control the amplitude or gain of the signals, which is specifically managed by the sensitivity switch.