Sunday, March 11, 2012

LASER therapy in physiotherapy

Synonyms: 
•    Therapeutic Laser
•    Low Level Laser Therapy
•    Low Power Laser Therapy
•    Low Level Laser
•    Low Power Laser
•    Low-energy Laser
•    Soft Laser
•    Low-reactive-level Laser
•    Low-intensity-level Laser
•    Photobiostimulation Laser
•    Photobiomodulation Laser
•    Mid-Laser
•    Medical Laser
•    Biostimulating Laser
•    Bioregulating Laser

4 categories of lasers
–    Crystal & Glass (solid - rod)
•    Synthetic ruby & others (synthetic ensures purity)

–    Gas (chamber) – 1961
•    HeNe, argon, CO2, & others

–    Semiconductor (diode - channel) - 1962
•    Gallium Arsenide (GaAs under investigation)

–    Liquid (Dye) - Organic dyes as lasing medium

–    Chemical – extremely high powered, frequently used for military purposes

Types of laser:

Lasers are of 3 different type soft laser, mid laser, power laser. Soft lasers are used for dermatological purposes where depth of penetration is only superficial, Physiotherapy lasers are mid lasers where depth of penetration is from .5-2cm for class III lasers up to 10 cm in type IV lasers. Power lasers are destructive lasers used in different medical & dental surgery.
There are 4 different classes of laser i.e. Class I-IV. All 4 class are used in physiotherapy. However class I-III lasers are commonly used. Class IV physiotherapy & surgical lasers are not to be confused with each other.

Class of lasers:

Class I: Low power lasers
Class II: Power out put up to 1mW (400-700 nm wavelength).
Class IIIa: Power out put up to 5mW.
Class IIIb: Power out put up to 5-500mW.
Class IV: Power out put up to 500-7500mW.

* All lasers can cause eye damage except Class I laser. As the power increases the potential of causing eye damage is more.

* Class III lasers are also known as LLLT i.e. low level laser therapy.

* Class IV lasers are also known as high power laser therapy.

* High-power lasers (class IV) have power output of up to 7,500 mW; and supposedly offer more power, deeper penetration (can penetrate up to 10 cm instead of 0.5 to 2.0 cm for class III lasers) and a larger surface treatment area (cover up to 77 cm2 instead of 0.3 to 5.0 cm2 for class III lasers) 

Modes of Laser:

Either it is continuous or Pulsed. In pulsed laser frequency is a key area for therapeutic efficiency.

Why red or IR lasers are used?
•    Red light affects all cell types
–    Absorbed by the mitochondrial present in all cells
–    Cytochromes (respiratory chain enzymes) within the mitochondria have been identified as the primary biostimulation chromophores (primary light-absorbing molecules).
–    Since enzymes are catalysts with the capability of processing thousands of substrate molecules, they provide amplification of initiation of a biological response with light.

•    Infrared light is more selective absorbed by specific proteins in the cell membrane & affects permeability directly

Tissue response:

•    Magnitude of tissue’s reaction are based on physical characteristics of:
–    Output wavelength/frequency
–    Density of power
–    Duration of treatment
–    Vascularity of target tissues

•    Direct effect - occurs from absorption of photons
•    Indirect effect – produced by chemical events caused by interaction of photons emitted from laser & the tissues

Patient & Laser parameters:

•    Patient parameters
–    Need medical history & proper diagnosis
•    Diabetes – may alter clinical efficacy
–    Medications
•    Photosensitivity (antibiotics)
–    Pigmentation
•    Dark skin absorbs light energy better

 Laser Parameters

–    Wavelength
–    Output power
–    Average power
–    Intensity
–    Dosage

Laser Wavelength:
This is measured in Nanometers (nm). Longer wavelength (lower frequency) imparts greater penetration. Wavelength is affected by power.

Laser output:
It is measured in Watts or milliwatts (W or mW). It is important in categorizing laser for safety. It is not adjustable.

Power Density or Laser intensity:
Beam diameter determines power density. Units of measurement is W or mW/cm2.It takes into consideration actual beam diameter. If light spread over lager area then there is there is lower power density.

Average Power:
It is dependant on the mode of laser beam delivery i.e. Continuous or pulse-train (burst) frequency mode. Knowing average power is important in determining dosage with pulsed laser. If laser is continuous laser then avg. power = peak output power. If laser is pulsed (burst) then avg. power is = to peak output power multiplied by duty cycle (frequency).

DOSAGE: Laser dosage is amount of energy applied per unit area. It is measured in Joules/square cm (J/cm2). Joule is unit of energy &1 Joule = 1 W/sec. Dosage is dependent on:
–    Output of laser in mW
–    Time of exposure in seconds
–    Beam surface area of laser in cm2
Various dosage ranges per site (1-9 J/cm2).

Recommended Dosage Range
–    Therapeutic response = 0.001-10 J/cm2
–    Minimal window threshold to elicit response
–    Too much – suppressive effect
–    Open wounds – 0.5-1.0 J/cm2
–    Intact skin – 2.0-4.0 J/cm2
–    Average treatment – 6 J /cm2

Different common lasers in physiotherapy:

1. Helium-Neon Lasers

•    Uses a gas mixture in a pressurized tube
•    Now available in semiconductor laser
•    Emits red light
•    Wavelength:  632.8 nm
•    Power output: 1.0-25.0 mW
•    Energy depth: 6-10 mm
•    The higher the output of the lasers (even though they are still low power) lower the delivery time

2. Indium-Gallium-Aluminum-Phosphide Lasers

•    InGaAip
•    Replacing HeNe lasers
•    Semiconductor
•    Wavelength:    630-700 nm
•    Power output:  same as HeNe
•    Energy depth: superficial wound care

3. Gallium ArsenideLasers

•    Semiconductor - produces an infrared (invisible) laser
•    Wavelength:  904–910 nm
•    Power output: may produce up to 100 mW
•    Energy depth: 30-50 mm
•    Short pulse-train (burst) duration (100-200 ns)

4. Gallium Aluminum ArsenideLasers

•    GaAIAs
•    Semiconductor
•    Wavelength: 780-890 nm
•    Power Output: 30-100 mW (up to 1000 mW)
•    Energy Depth: Very high more than the above said laser

Laser Application techniques:

•    Gridding Technique
•    Divide treatment areas into grids of square centimeters
•    Scanning Technique
•    No contact between laser tip in skin; tip is held 5-10 mm from wound
•    Wanding Technique
•    A grid area is bathed with the laser in an oscillating fashion; distance should be no farther than 1 cm from skin
•    Point Application (On acupuncture point)

Treatment techniques for contact treatment:

Dosage is the most important variable in laser therapy & may be difficult to determine. However it may be simplified i.e. for general application, only treatment time & pulse rate vary. Usually there is a handheld applicator & tip should be in light contact with skin while laser is engaged for pre-calculated time. Maintain laser perpendicular to treatment surface. Put firm contact unless open wound. Clean area prior to treatment.

Always begin with minimal treatment and gradually increase (Better to underexpose than to overexpose). Check for pre/post-treatment changes. Ask the patient how they are doing prior to next treatment because you may have to adjust dosage.

Avoid direct exposure into eyes (If lasing for extended periods of time, safety glasses are recommended). May experience a syncope episode during treatment during chronic pain, but it is very rarely reported.

Application of heat & cold with LASER:
If icing – use BEFORE phototherapy because it enhances light penetration. If using heat therapy – use AFTER phototherapy because it decreases light penetration.



Use of Laser therapy in different field of medicine

1. Vascular condition: Venous ulcer (Ref: M.E. Sugrue et al; Annals of Vascular Surgery, Volume 4, Issue 2 , Pages 179-181, March 1990). Results of this pilot study are encouraging. Raynaud's phenomenon is also treated by Laser therapy (Hirschl et al, 2004). Popularly pressure ulcers are treated by laser therapy in neurorehab words.

2. Neurological condition: Stroke (Ref: Int J Stroke. 2012 Feb 2. doi: 10.1111/j.1747-4949.2011.00754.x.). This study named transcranial laser therapy for acute ischemic stroke: a pooled analysis of NEST-1 and NEST-2, support the likelihood that transcranial laser therapy is effective for the treatment of acute ischemic stroke when initiated within 24 h of stroke onset. If ultimately confirmed, transcranial laser therapy will change management and improve outcomes of far more patients with acute ischemic stroke.

Similarly laser therapy is also reported to be beneficial in number of other neurological conditions both in animal & human subjects. Examples are closed-head traumatic brain injury (mice)( In mice it is reported that there is less neurological deficits in post-traumatic brain injury treated with laser for traumatic brain injury.), neurodegenerative diseases (humans) example Alzheimer’s disease. 

3. ENT conditions: Tonsillitis (Vestn Otorinolaringol. 2006;(3):19-22. Russian.), Tinnitus (FrankW et al; GMS Health Technol Assess. 2006 Aug 30;2:Doc17).

4. Surgical conditions: Chronic wound healing, Kaviani and colleagues (2006) examined the effects of low level laser therapy (LLLT) in the treatment of post-mastectomy lymphedema & concluded that LLLT has encouraging results on this condition. LLLT can be used as a conservative therapy for arm lymphoedema secondary to breast cancer treatment (BC Cancer Agency; 2007). Mastodynia is also treated successfully. Lymphangitis is also reported to be treated successfully

5. Dental conditions: post-operative pain after endodontic surgery (Kreisler et al; 2004). Markovic and Todorovic (2007) found after lower third molar surgery laser therapy can be recommended to minimize swelling & oedema. TMJ conditions also show encouraging results.

6. Musculoskeletal conditions: Bursitis, Tendinitis, Ligament injuries, CTS, Neck pain, LBA, myofascial pain syndrome (MPS), Post exercise pain (to treat plyometric induced pain), planter heel pain(Crawford and Thomson, 2003; Landorf and Menz, 2007).

7. Rheumatological conditions: RA (most studied) other rheumatologic pain

8. Other conditions: After effects of tuberculosis, Smoking cessation, Dysmenorrhea etc. 








   

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