PS 200 - Notes - Week 12 - Biofeedback, Laser, and Shortwave Diathermy

Biofeedback, Laser, and Shortwave Diathermy

Biofeedback

• Biofeedback is a method of controlling a system by reinserting the results of its past performance, allowing patients to see their progress and adjust their actions for better performance.
• It's particularly useful as an adjunct to facilitate a patient's exercise and motor control.

The Biofeedback Loop:

1. Motor Planning: The decision to move originates in the cerebral cortex.
2. Muscle Activity: Messages are sent to the muscles to generate movement.
3. Outcome: The result of the movement is evaluated against the initial motor plan.
4. Feedback:
   • Successful outcome reinforces the motor pattern.
   • Unsuccessful outcome requires modification of motor planning and muscle activity.

• Example: Throwing a basketball. Adjusting the next throw based on the outcome of the previous one.

Types of Biofeedback:

• Pressure Biofeedback:
  • Uses pressure-sensitive devices like a sphygmometer or the blue stabilizer unit.
  • Commonly used for lumbar stability exercises and core stability.
  • The goal is to maintain consistent pressure while moving limbs, indicating true stability.
• Real-Time Ultrasound:
  • Used to identify transverse abdominis activity, though its role in core stability is debated.
  • Helps patients selectively contract the transverse abdominis.
• Surface EMG (Electromyography):
  • Records electrical activity in muscles to either up-train (increase activity) or down-train (reduce activity).
  • Examples:
    • Down-training overactive common extensor origin muscles in writers to prevent lateral epicondylitis.
    • Up-training the vastus medialis obliquus (VMO) to correct patellar maltracking.
    • Reducing activity in the frontalis and temporalis muscles to alleviate stress headaches.
• Heart Rate Monitors: Provide feedback on exercise intensity.
• Mirrors: Allow patients to visually monitor and correct their movements, particularly in postural control and gait re-education.

Uses of Biofeedback:

• Assessment:
  • Identifies overactive or underactive muscles using surface EMG.
• Treatment:
  • Up-train or down-train muscles by providing real-time feedback.

Open Loop vs. Closed Loop Feedback:

• Open Loop Feedback:
  • There is a time delay between the motor activity and the feedback.
  • Example: Throwing a ball; the outcome is not immediately known.
  • Makes learning more difficult because of the delayed modification.
• Closed Loop Feedback:
  • Feedback occurs immediately as the movement is performed.
  • Example: Steering a car; visual feedback allows instant correction.
  • Facilitates easier and quicker learning.
• The goal is to provide closed-loop feedback to enhance learning.

Skill Acquisition (Fitts and Posner Model):

1. Cognitive Phase:
   • The patient is thinking a lot about the movement and exercise execution.
   • Requires high brain activity and focus.
2. Associative Phase:
   • The patient starts to chunk activities together.
   • Skills become more coordinated.
3. Autonomous Phase:
   • The activity becomes automatic.
   • Requires minimal conscious thought.

• Example: Learning to drive a car, progressing from conscious effort to automatic execution.
• Biofeedback assists in progressing patients from the cognitive to autonomous phases.

Surface EMG Details:

• Records electrical activity from muscles, proportional to muscle contraction.
• Limitations:
  • Primarily records activity in superficial muscles.
  • Larger electrodes may cause crosstalk (picking up activity from adjacent muscles).
  • Smaller electrodes are needed for accurate measurement in small muscles.

Electrode Placement:

• Two active electrodes are placed along the muscle belly to record electrical activity.
• A ground electrode is placed over a bony area or where no muscle contraction is expected, to minimize environmental electrical noise.
• Good contact is essential (use alcohol wipes or shave the skin).

Pressure Biofeedback for Lumbar Stability:

• A pressure-sensitive device is placed under the low back.
• The patient performs posterior and anterior pelvic tilts to find a neutral position, typically around 40 mmHg.
• The goal is to maintain this pressure while lifting legs, assessing core stability.
• True core stability means the lumbar spine remains locked in a neutral position during limb movements.

General Biofeedback Tips:

• Use mirrors for postural control and gait re-education.
• Surface EMG serves as a motivator and teaching tool.
• Adjust communication style based on the goal (loud for up-training, calm for down-training).
• Monitor for fatigue.
• Ensure the patient's starting position is correct.
• Continuously reset goals and progress the patient.

Contraindications and Precautions:

• Few contraindications, as biofeedback merely records energy rather than injecting it.
• Possible allergy to adhesive electrodes.
• Inability to understand instructions or interpret the signal, leading to frustration.
• Fatigue.
• Considerations specific to the movement dysfunction being treated.
• Biofeedback is a valuable adjunct to motor skill training, not strength training.

Laser

• Laser stands for Light Amplification by Stimulated Emission of Radiation.
• It is a coherent light, both temporally and spatially, unlike ordinary white light.
• Follows the same properties as other electromagnetic waves like reflection, refraction, absorption, and scattering.

Laser Types:

• Low Power Lasers (Level 1): Safe for eyes and skin (e.g., supermarket barcode readers).
• Level 2: Safe for skin but requires eye protection.
• Level 3 (a & b): Used in physiotherapy; require caution and eye protection.
• Level 4: High-powered; hazardous to skin and eyes (used in surgical techniques).
• Physiotherapy uses low to medium power lasers (under 500mW), also known as cold lasers or low-level lasers, which don't generate heat and are athermal.

Application Methods:

• Probe
• Scanning System
• Cluster Probe (multiple probes together)

Physiological Effects:

• Photochemical effect stimulates mitochondria and cell membranes.
• Facilitates physiological changes and the healing cascade.
• Superficial penetration (about 1-1.5 cm).

Therapeutic Effects:

• Tissue healing
• Pain relief
• Reduction of edema
• All effects are related to accelerating the healing cascade.

Dosage:

• Based on energy density (joules per centimeter squared).
  • Acute injury: 0.5 to 4 J/cm²
  • Chronic injury: Higher energy levels
• Shorlt's Law: The more injuries heal, the more energy they can take.
• Energetic entities in the range of 0.5 to 4 would be most effective in triggering a photobiological response in tissue with $4 J$ having the potential greatest effect on wound healing. Greater than that at age 12 appear to have a bioinhibition effect.

Dosage Calculation:

• Formula: $Treatment Time = \frac{Required Energy Density}{Power of Machine \times Cross Section of Laser Treatment Area}$
• Most modern machines calculate dosage automatically.

Precautions:

• Eye Damage:
  • Everyone must wear eye protection.
  • Use in a treatment room with a door, not curtains.
  • Signage outside the door indicating laser use.
  • Patients should have a hand control to cut the laser if necessary.
• Risk of infection with open wounds.
• Inability to communicate (general precaution).
• Existing conditions that may be stimulated.
• Photosensitivity or reduced skin sensation.

Contraindications:

• Tumors (especially skin cancers).
• Pelvic area during pregnancy (precautionary).
• Areas of dividing cells (eyes and testes).
• Infected tissue.
• Over the sympathetic ganglion or cardiac area in patients with heart problems.
• Avoid the thoracic spine in patients with coronopathies.

Practical Application:

1. Ensure patient comfort.
2. Obtain informed consent.
3. Wipe the skin with alcohol.
4. Calculate dosage or select appropriate settings.
5. Ensure everyone wears glasses.
6. Apply the probe to the skin or slightly above it.
7. Use spot, scanning, or grid techniques to cover the treatment area.

Shortwave Diathermy

• A form of deep heat using high-frequency electrical current between two electrodes.
• Generates electromagnetic waves, producing heat deep within the tissue.
• Frequency: $27.12 MHz$

Application Methods:

1. Capacitive Method:
   • The body is placed between two capacitive plates.
   • High-frequency alternating current flows between the plates, generating heat.
   • Can be coplanar (superficial heating) or deep through the tissue.
2. Inductive Method:
   • An electrical current generates an electromagnetic field.
   • This field produces induction or eddy currents, generating heat within the body.
   • Greater heating in tissues with low resistance (water and muscle).
   • Uses a shortwave diathermy cable wrapped around the limb.

• Capacitive method (plates) is more common than inductive (cables) due to usability.

Physical Effects:

• Thermal:
  • Deep heating with collagen extensibility, increased blood flow, and decreased tissue viscosity.
  • Deeper heating than other modalities (except ultrasound, but shortwave covers a larger area).
• Non-Thermal (Pulsed Shortwave):
  • Application of a low-dose electromagnetic field.
  • May stimulates cell membrane and mitochondria activity.
  • Facilitates ionic transfer across the cell membrane and stimulates the healing cascade.

Therapeutic Effects:

• Pain relief
• Wound healing
• Reducing joint stiffness (particularly useful before stretching, e.g., in adhesive capsulitis)

Precautions:

• Pregnancy
• Menstruation
• Epiphyseal Plates in Adolescents
• Metal Implants/Jewellery
• Areas of high fluid content (e.g., wet dressings, oedema)
• Impaired Circulation
• Sensory Impairment
• Obesity

Contraindications:

• Cardiac pacemakers
• Metal implants (localized)
• Pregnancy
• Malignancy
• Infected tissues
• Acute inflammation
• Areas of hemorrhage
• Thrombophlebitis/DVT
• Tuberculosis
• Impaired sensation
• Severe circulatory compromise