Cold laser

COLD LASER: 

COLD LASER Dr . HANY ZAHRAN M.D. Head Of Rheumatology & Rehabilitation, H 6 October University

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COLD LASER The use of light for therapeutic purposes dates back to the ancient Greeks, Romans, and Egyptians. Current research into the physiologic benefits of light therapy has developed an area of great interest: the laser.

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Definition The popularly used term, laser, is an acronym for Light Amplification by Stimulated Emission of Radiation. The power levels of light are greatly amplified by the emission of radiation, from stimulation of specific substan ­ ces.

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Every substance radiates emissions in varying wave lengths / frequencies. Helium, neon, cobalt, and carbon dioxide arc examples of substances that, when irradiated, have application in commercial, medical, or engineering processes.

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In therapeutic use of laser, we are concerned with the emissions of a helium/neon (He/Ne) mixture in the 6,328 °A unit band of the spectrum.

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Other medically useful lasers are in the 9040 °A unit (infrared) band e.g.-CO2 10,600 °A units; and the ruby, 6943 °A units, but most of these, however, are used in surgical procedures e.g. Ruby in Optha]niology and Dermatology; Neodymium YAG is used in endobronchial surgery and in gastroentrology;

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Argon is used in Oplhalmology, Dermatology and Gastroenterology; Argon is used in Gynaecology, Otolarngology, Neurosurgery, Plastic and General Surgery. However, the HeNe 6,328 °A unit laser is utilized in physical therapy.

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MECHANICS To obtain the laser, a tube filled with a gaseous mixture of helium and neon is stimulated electrically to emission levels. Within the highly reflective, polished walls of the tube, the molecules reverberate and carom off the walls in a highly agitated state, building energy as they do so.

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When a critical level is reached, the flow of energy literally “ bursts ” through the semisilvered (similar to a one-way mirror) front end of the tube and is channeled along an optic fiber to the beam applicator, or probe, for clinical applications.

PHYSICS : 

PHYSICS Intensity One might naturally assume that the laser generates tremendous power; however, the type of laser used by physical therapists has the intensity of only 1mW-less than the power of a 60-W commonly used light bulb.

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The commercial and industrial lasers (i.e., hot lasers) range in the thousands and millions of watts and are used for cutting, drilling, and destructive applications. The tool used by physical therapists, a cold laser, is used primarily for healing and other nondestructive purposes.

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Physical Characteristics There are three characteristics of laser light that clearly differentiate it from ordinary light.

1. Monochromaticity: 

1. Monochromaticity Ordinary light is comprised of a conglomeration of many wave lengths, com ­ monly known as ROYGBIV, or the visible spectrum of Red, Orange, Yellow, Green, Blue, Indigo, and Violet, all merging to produce "white" light. Laser light, however, consists of one wave length only which is 6,328 °A units. Be ­ cause this wave length falls within the R section of the visible spectrum (3,900 to 7,700 °A units), the laser light of 6,328 °A units is a brilliant red color.

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2. Coherence Because the wave lengths of ordinary light are so variable and do not "match" in wave forms, frequencies, or shapes, there is much scrambling of wave forms, cancellations and reinforcements of individual waves, and inter ­ ference in the production of energy in general; this factor minimizes the power of ordinary light as an energy source.

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The identical wave lengths and forms, that comprise laser light, lead to great amplification since the "waves and troughs" of the radiation are reinforced. Because they are parallel and in line with each other, they are termed coherent.

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3. Non-divergence The laser beam is unique in the absolute "straightness" of the directed radiation. Ordinary light shines in all directions (e.g., consider a light bulb radiating In all directions). The sun is another example of omnidirectional radiation.

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The laser, on the other hand, shines in only one direction, not unlike a Hash-light, although its beam is far more concentrated and narrowed. The divergence of a laser beamed to the surface of the Moon from Earth showed a deflection of just a few meters after a journey of more than 260,000 miles.

PHYSIOLOGY: 

PHYSIOLOGY Wound Healing Ordinary light does not penetrate the skin or underlying tissues. Only the retina can absorb the visible spectrum.

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As discussed previously, infrared is ab ­ sorbed at the 3-imn level and ultraviolet at the 1-mn level. Research has in ­ dicated that the 6,328 A unit wave length of the cold laser may stimulate intracellular structures and functions.

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One of the prime applications of laser light in physical therapy is that of wound healing.

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Analgesic Effects In pain control, the penetration of laser light is often compared with an acupuncture needle. Therefore , when the laser is used for analgesic purposes, the beam is generally directed at acupuncture points, trigger points, and nerve roots, as is done with acupuncture.

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Penetration Direct penetration of the 6,328 A unit HeNe cold laser at 1 mW is said to be approximately 0.8 mm; indirect penetration after refraction, dispersion, reflection, and partial absorption is 10 to 12 mm.

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Absorption Absorption is apparently dependent on the resonance of the tissues or on the subject's water content. Many of the penetration characteristics and limita ­ tion factors are determined by fluids (e.g., water, blood).

PHYS1CAL EFFECTS: 

PHYS1CAL EFFECTS Heating A mild but reversible heat is produced with the cold laser. The tissues revert back to the pre-lasting temperatures immediately following radiation.

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Al ­ though the thermodynamics involved do not produce a therapeutic level, cell wall permeability has been shown to be a favorable result of heat and may play a role in the reaction of the laser on the cell wall.

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Dehydration Loss of water following radiation is another reversible process. Such loss may be attributed to the minor heating and/or the transfer of fluids to distant sites. Apparently, it does not play a major role in the laser's effectiveness.

Coagulation of Proteins, Thermolysis, and Evaporation: 

Coagulation of Proteins, Thermolysis, and Evaporation Coagulation of proteins, thermolysis, and evaporation are irreversible and should not occur with the dosages and techniques used by physical therapists.

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Coagulation is a permanent process, comparable to that of an egg frying in a skillet. Thermolysis, or "melting from heat," is also a lasting state. Evapora ­ tion, of course, involves the transformation of liquids to the gaseous state and is not easily reversed.

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With competent clinicians and sophisticated equipment, none of these conditions should be produced in routine administration of the cold laser. With higher power levels, one must be cautious and aware of the above factors.

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DOSAGES Actual dosages with the cold laser depend on the power factor, duration of radiation, and tissue resonance.

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Wound Healing In most wound healing applications, the prescribed dosage is 90 sec/cm of open lesion. This may retire several minutes of hand-held direction of the beam over the surface of the wound so that each square centimeter, is exposed for the same 90 seconds.

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The probe tip is held approximately 2 to 3 mm from the surface to obtain a "disc" of laser light about 1 cm in diameter on the surface face of the wound. The nondivergent nature of the laser lenslike spreading of the beam for therapeutic purposes.

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Pain Control At acupuncture and trigger points, nerve roots, and pain sites a dosage of 15 to 30 seconds for each point is recommended. Unlike in the open wound technique, the probe tip is held in contact with the skin at these points during the procedure.

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MODES Current laser equipment offers two modes: continuous and pulsed beams. Continuous Beam The continuous mode is recommended for acute pain and fresh wounds,

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Pulsed Beam The pulsed mode has been found more effective with chronic conditions. Pulsed models vary from 1 to 80 pulses per second, depending on the manufac ­ turer. One suggested technique for chronic pain or long-standing open lesions would be in the range of 4 to 10 pulses per second.

PARAMETER SETTINGS: 

PARAMETER SETTINGS Current laser units offer manual timing or automatically timed treatments. For longer exposures, such as with large open wounds, use of the automatic timer is suggested. For pain control, either manual or automatic timing may be utilized. Power levels are pre-set by the manufacturer and the FDA at 1 mW; however, the power is reduced to almost half (0.5 mW) when the pulsed mode is in effect.

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PROBE DATA The cold laser equipment includes a probe, from which the laser beam is emitted through an opening in the tip.

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This tip also serves as a differential resistance device ( ohmetcr ) to locate the points of lowest resistance for acupuncture like applications of the laser (Acupuncture points are points of low electrical resistance as compared with the surrounding skin).

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A visual, digital read-out on an lighted electronic display (LED) is available to the clinician, along with an audible signal, preset to sound at a specific microampere level (e.g., 30 mA on the LED). This is extremely helpful when the clinician is searching with the LED for target point that are out of the range of sight.

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The probe, when utilized for point searching, requires the use of a ground electrode, usually a hand-held, metallic cylinder, connected to the chassis by a separate but integrated circuit.

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When this cylinder is used, the patient grasps the ground cylinder while the physical therapist searches the patient's skin for proper points and then applies the laser beam to them.

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The ground is not necessary when treating open wounds since there is no skin contact during the treatment and the target site is obvious. The audible volume of the signal is controlled by the clinician.

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Some of the more recently marketed units also include simultaneous or separate electrical stimulation modes with the laser circuit. The tip on these units functions as an electrode, and the ground cylinder functions as a secon ­ dary electrode to complete the circuit.

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Various wave forms of electrical stimulation (e.g., square-wave , sine-wave, spike - wave ) are offered on these units. When the 9,040 °A unit infrared laser is available as an optional wave length with units, the probe may also contain a guide light for operation, since the in ­ frared beam is invisible.

INDICATIONS: 

INDICATIONS Cold laser is indicated for treating 1. Open lesions. 2. Decubitus ulcers. 3. Diabetic ulcers. 4. Lacerations 5. Incisions.

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6. Burns. 7. Chronic and acute pain especially those of musculoskeletal origin. For example, arthritis, sprains tendonitis, contusions, lumbago, neuralgia, neuritis. 8. Restricted joint ranges of motion.

However, medical laser Is used in:: 

However, medical laser Is used in: 1- Ophthalmology': Helium Neon, Argon ruby and krypton. 2- Surgery: • HeNe arid Low CO2, irradiation of chronic ulcer, bed sores. • CO2 laser for excision of ulcer, mass tumors. . • Nd YAG for anal operation (piles)

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3- Obstetrics and gynaecology: CO2, Hc-Ne, ND YAG. 4-E.N.T. Co2 scalpel for tumour surgery.

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5- Skin disease. • CO2, for cauterization • Hc-Ne for irradiation of chronic ulcer to help closure of wound surface. • ND YAG for deep lesion such as hacmingiorna

CONTRAINDICATIONS : 

CONTRAINDICATIONS 1 . Do not radiate the eye directly. 2. Whether pregnancy is a contraindication to use of the laser has not yet been determined, but the laser is suspect due to its mobilizing effect on steroids in the human system.

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3. Do not use the laser with patients who are naturally photosensitive or who are photosensitized by medications. 4. Patients with pacemakers (since the electronic circuits of the laser sys ­ tem could interfere with the operation of the pacemaker).

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5.Patients with left ventricular insufficiency under treatment for poor peripheral circulation (since laser treatment might produce a dangerous overloading of the central venous system). 6. Patients with recent heart attacks.

The following areas should never be irradiated; : 

The following areas should never be irradiated; 1. Eyes and pregnant uterus as mentioned above. 2. Thyroid glands (due to the possibility of increased hormone secretion).

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3.Male external genitalia (due to the possibility of interaction with the cells of the germinal line or the endocrine portion of the testicle). 4.Skin if there is cutaneous or subcutaneous bacteria] infections. 5.Growing cartilage in children.

PRECAUTIONS: 

PRECAUTIONS Poor results may ensue in patients 1. Of extreme age 2. Under heavy medication 3. With considerable scar tissue 4. With extremely dry skin 5. With active infection

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A touch of moisture on the tip of the probe or the target skin may enhance the electrical contact needed for efficient point searching. Perspiration or other skin moisture will naturally give false read-outs; adjustments must be made in such circumstances. Dry the patient's skin prior to lasing and/or select higher readings on the LED for targeting.

TREATMENT PROCEDURES: 

TREATMENT PROCEDURES 1. Tissue Heating a. Ordinary Wounds 1. No ground is required. 2. Select continuous mode if the wound is fresh; use pulsed mode at 10 pul ­ ses per second if the wound is old.

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3. Radiate for 90 see/cm2 at a distance of 2 mm from the patient's skin, with slow movement of The probe to cover the entire wound area. 4. The red disc that appears on the skin should be about 1 cm in diameter.

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b. Extensive Wounds 1. Radiate the perimeter (edge) of the wound with a slowly moving probe. 2. Cover each centimeter along the perimeter for 90 seconds. 3. As the wound closes (heals) with subsequent lasings, the central portion may be treated as described above.

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1. Grid Technique 1. The grid technique is also recommended for extensive lesions requiring long exposures. 2 . Mentally "grid" the wound into 1 cm sections and proceed to apply the laser to each action for the suggested 90 seconds.

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Frequency of Treatment With open wound procedures, treatment is administered two or three times weekly; results will be visible to the casual examiner within the first three or four treatments. Patience is required with larger wounds, scarred areas, scar tissue, tough skin, and infections.

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2. Pain Control 1. Use probe and ground cylinder. 2. Search the patient's skin in the area of known acupuncture points, pal ­ pable trigger points , nerve roots , and pain sites by lightly touching the probe tip to the skin (while the patient grips the ground cylinder ).

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3 . Monitor the LED for high read-outs, usually greater than 20 u A, or lis ­ ten for the audible signal at approximately 30 uA on the LED screen. 4. When the audible signal is heard, press the trigger on the probe handle, to activate the laser.

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5. Hold in contact with the point for 15 to 30 seconds. 6. If the automatic mode is in effect, it is not necessary to hold down the trigger since the laser will be "on" for the selected number of seconds on the timer dial.

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7.Small reddish marks will appear at the points of probe contact, especial ­ ly if the physical therapist has a "heavy hand"; however, the marks should disappear within 1 hour and cause no reason for concern. • Several factors have been postulated for the analgesic effect of laser: 1- Anti inflammatory 2- Conunter irritant

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3- Normalization of tissues: may restore the equilibrium of a cell energetic state. 4- Endorphine release. 5- Reabsorption of oedema fluid.

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Frequncy of treatment 1. Administer treatments daily if necessary and indicated by the severity of pain. 2. If favorable results are not noted by the third or fourth treatment, consider other modalities for analgesia.

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