Which of the patient's limbs serves as an electrical ground during ECG?

The correct choice for which limb serves as an electrical ground during an electrocardiogram (ECG) is the right leg. In an ECG setup, the right leg electrode is often used as the reference point or ground. This means that it helps to provide a stable, neutral point against which the electrical signals generated by the heart can be measured. The electrical signals from the heart create a potential difference between the limbs, which is what the ECG interprets to create the heart rhythm trace.

The choice of the right leg as the ground electrode is particularly important for minimizing noise and interference from other electrical sources while ensuring the accuracy of the heart's electrical activity recording. The other limbs, while also involved in the ECG leads, are primarily focused on capturing the electrical activity from the heart rather than serving as a grounding point.