Figure 1. Bipolar limb derivations-EKG Through Sound-Card

<p>Since the human body is a conductive mass, an electrode attached to the arm is the electric<br> equivalent of a connection to the shoulder and an electrode attached to the foot is the equivalent of a<br> connection to the abdomen. Using this principle, we obtain the following three standard bipolar<br> limb derivations (Figure1):<br> &bull; Derivation I: negative electrode to the right hand and positive electrode to the left hand<br> &bull; Derivation II: positive electrode to the left foot, negative to the right hand<br> &bull; Derivation III: positive electrode to the left foot, negative to the left hand.</p>