Why perform impedance checks before electrotherapy?

• A. To ensure proper contact and safe current delivery; high impedance indicates poor contact or dry skin requiring adjustment.
• B. To measure the patient's blood pressure.
• C. To determine the patient’s pain threshold.
• D. To adjust room lighting.

Answer: (A)

Impedance checks focus on making sure the current can flow from the device to the body through the electrode-skin interface in a predictable, safe way. Impedance is the opposition to that current flow. When impedance is low, contact is good and the prescribed current can be delivered reliably and evenly. If impedance is high, contact is poor—skin may be dry, dirty, oily, or hairy, electrodes may be dry or poorly placed, or there may be insufficient conductive gel. In that case, the current won’t travel consistently, which can lead to uneven stimulation, hotspots, or burns. So you adjust by improving contact—cleaning the skin, applying adequate conductive gel or lotion, repositioning or resecuring electrodes, or shaving hair as needed—and only proceed once the impedance is within the acceptable range. These checks are not about measuring blood pressure, pain threshold, or room lighting; they’re specific to ensuring safe, effective current delivery.