Module 9: Iontophoresis & Biofeedback

What is iontophoresis and how is it classified as a physical therapy modality?

Iontophoresis is a biophysical agent that uses direct electrical current to deliver ionized medication through intact skin. It is classified as an electrotherapeutic modality primarily used for localized drug delivery to reduce inflammation or pain.

What fundamental problem does iontophoresis solve compared to oral or injectable medications?

Iontophoresis allows medication to be delivered directly to the involved tissue while minimizing systemic absorption. This reduces the risk of systemic side effects and targets treatment to a specific anatomical region.

Why must iontophoresis use direct current (DC) rather than alternating current (AC)?

Direct current flows in one direction, which is required to create electrostatic repulsion. Alternating current reverses direction and would cancel the repulsive force needed to move medication ions through the skin.

Why is iontophoresis sometimes described as polarity-dependent drug delivery?

The movement of medication depends on electrical polarity. The active electrode must have the same charge as the medication so that like charges repel, driving the medication away from the electrode and into the tissue.

Why must the polarity of the active electrode match the charge of the medication?

Like electrical charges repel each other. Matching the polarity ensures the medication is pushed into the tissue rather than remaining concentrated under the electrode, which would reduce effectiveness.

Why is dexamethasone delivered using the negative electrode (cathode)?

Dexamethasone is negatively charged. Placing it under the cathode causes electrostatic repulsion that drives the medication into the tissue.

Why is lidocaine delivered using the positive electrode (anode)?

Lidocaine carries a positive charge, so it must be placed under the anode for effective delivery via repulsion.

What happens clinically if the incorrect polarity is selected?

If polarity is incorrect, medication delivery is ineffective, and the patient may receive little to no therapeutic benefit despite undergoing treatment.

What does the dosage unit mA·min represent in iontophoresis?

mA·min represents total electrical dose and is calculated by multiplying current amplitude (mA) by treatment time (minutes). It allows clinicians to adjust intensity and duration while keeping total dose constant.

Why can dosage be adjusted by changing current intensity or treatment time?

Lower intensity can be compensated by longer treatment time to maintain total dose, which may improve patient comfort while still achieving therapeutic effects.

Why do chemical skin reactions occur during iontophoresis?

A. Direct current causes electrochemical reactions at the skin–electrode interface, leading to acidic or alkaline byproducts depending on electrode polarity.

Why are alkaline reactions under the cathode more dangerous than acidic reactions?

Alkaline reactions form sodium hydroxide, which is more caustic and increases the risk of skin irritation or chemical burns compared to acidic reactions.

How should a PTA monitor the skin during and after iontophoresis?

The PTA should inspect the skin before and after treatment, monitor patient sensation throughout, and discontinue treatment if excessive redness, blistering, or burning occurs.

What conditions are commonly treated with iontophoresis according to the lab sheet?

Common indications include tendinitis, bursitis, lateral epicondylitis, plantar fasciitis, and other localized inflammatory conditions.

Why is iontophoresis appropriate for conditions like plantar fasciitis or lateral epicondylitis?

These conditions involve localized inflammation in superficial tissues, making them ideal for targeted medication delivery without systemic exposure.

Why is iontophoresis contraindicated in patients with pacemakers or implanted electrical devices?

Direct current may interfere with the function of implanted electrical devices, creating a serious safety risk.

Why is impaired sensation a contraindication or strong precaution?

Patients must be able to report burning or discomfort. Impaired sensation increases the risk of unrecognized skin injury.

Why is iontophoresis contraindicated over open wounds or broken skin?

Broken skin alters electrical resistance and increases the risk of chemical burns and uncontrolled medication absorption.

What is biofeedback and how does it differ from other electrotherapeutic modalities?

Biofeedback provides real-time visual or auditory information about muscle activity without electrically stimulating the muscle. The patient generates the contraction voluntarily.

What primary clinical problem does biofeedback address?

Biofeedback addresses impaired neuromuscular control, helping patients learn to activate or relax muscles appropriately.

Why is biofeedback considered a motor learning tool?

It reinforces the connection between patient effort and muscle response, allowing the nervous system to relearn proper activation patterns.

Why are biofeedback electrodes placed parallel to muscle fibers?

Parallel placement improves signal detection accuracy by aligning with the direction of muscle fiber activation.

Why is high sensitivity used for muscle relaxation training?

High sensitivity detects even minimal muscle activity, helping patients learn to fully relax overactive muscles

Why is lower sensitivity used for strengthening or facilitation?

Lower sensitivity requires stronger muscle activation to trigger feedback, encouraging active recruitment.

What conditions commonly benefit from biofeedback?

Biofeedback is useful for hemiplegia, post-surgical inhibition, pelvic floor dysfunction, and muscle guarding conditions.

Why is biofeedback contraindicated when muscle contraction is detrimental?

Encouraging muscle activity could worsen tissue damage or compromise healing in certain conditions.

Why should biofeedback be paired with functional task training?

Improved muscle awareness must be integrated into functional movements to produce meaningful carryover.

What type of electrical current is required for iontophoresis and why?

Iontophoresis requires direct current (DC). DC flows in one direction, which is necessary to create electrostatic repulsion to drive charged medication ions through the skin.

What is the typical dosage range used in iontophoresis treatments?

Typical iontophoresis dosages range from 40 to 80 mA·min, depending on medication, skin tolerance, and clinical goal.

What is a common standard dosage used in PTA labs and exams?

A commonly taught standard dosage is 40 mA·min, as it balances medication delivery with skin safety.

How can a PTA modify dosage while maintaining the same total dose?

The PTA may lower current intensity and increase treatment time, or increase intensity and shorten time, as long as the total mA·min remains the same.

What intensity range is commonly used during iontophoresis?

Intensity is typically set between 1 and 4 mA, depending on patient tolerance and electrode size.

Why is lower current intensity preferred in iontophoresis?

Lower intensity reduces the risk of skin irritation and chemical burns caused by DC electrochemical reactions.

How is treatment time determined in iontophoresis?

Treatment time is calculated based on desired total dosage and selected current intensity.

What treatment time results from a 40 mA·min dose at 4 mA?

A 40 mA·min dose delivered at 4 mA requires 10 minutes of treatment time.

What treatment time results from a 40 mA·min dose at 2 mA?

A 40 mA·min dose delivered at 2 mA requires 20 minutes of treatment time.

Why is a larger dispersive electrode used in iontophoresis?

A larger dispersive electrode lowers current density, reducing the risk of skin irritation and burns.

Why must the active electrode containing medication be smaller?

A smaller active electrode increases current density at the treatment site, improving medication delivery efficiency.

What precautions reduce skin irritation risk during iontophoresis?

Using appropriate electrode size, limiting dosage, inspecting skin before and after treatment, and monitoring patient sensation.