Continuous emission EQ Pro transducers (Red Transducer and Yellow Transducer) can produce a significant temperature increase in deep tissues, while avoiding excessive heating of overlying tissues. Therefore EQ Pro Therapy can be used to heat specific equine structures (such as joints, tendons, ligaments and muscles), without overheating the skin.

Factors affecting heat depth and diffusion are:

• ultrasound frequency
• intensity of ultrasound emission
• treatment duration
• size of the area to treat
• type of tissue to treat

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The higher the frequency, the greater the amount of energy absorbed by superficial tissues and consequently the more superficial the thermal effects.

This is one of the main advantages offered by EQultrasound Pro low-frequency treatment modality (38 kHz +/-2) versus traditional high frequency ultrasound devices (1-3 MHz): since EQultrasound Pro Therapy operates at a much lower frequency than traditional high frequency devices, it can reach deeper equine tissues and structures with limited absorption by superficial tissues.

In fact ultrasound energy is attenuated when the wave propagates through biological tissues. Attenuation is the result of absorption and scattering effects. Absorption in tissue leads to the transformation of ultrasound energy into heat, and is the main component of attenuation.

The temperature induced in tissue is directly proportional to its absorption coefficient. Biological tissues with a high fluid content absorb ultrasound waves better than less hydrated tissues.

Ultrasound does not appreciably heat skin but can significantly heat deeper tissues such as joint structures, tendon, muscle, nerve, and bone. Continuous emission modality is usually employed for pathologies in the chronic phase or when heat is a desirable element (for example to increase soft tissue extensibility before active or passive stretching activities).

Heating biological tissues using EQultrasound Pro Therapy continuous mode administration induces the following physiological effects:

• decrease of viscosity in fluid elements
• increase in vasodilation and blood flow (which convey more oxygen and nutrients to the injured area and assist in the reduction of swelling)
• increase in enzymatic activity
• increase in cellular metabolic activity, accelerating oxygen consumption and removal of waste substances generated by the injury (histamine, bradykinin and prostaglandins, which contribute to sensitization of nerve fibers and pain)
• stimulation of the immune system
• pain relief
• increase in soft tissue extensibility

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Therapeutic continuous emission ultrasound is commonly used for:

• chronic inflammatory conditions
• prior to stretching exercises of a tight structure (tendon, ligament, fascia, scar, capsule)

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Deep heat induced by continuous emission ultrasound stimulates tissue repair in chronic inflammatory conditions and is a valuable tool for veterinarians and equine physical therapists, since it enables them to treat specific areas most often affected in sports injuries, while avoiding excessive heating of overlying skin.

Continuous emission EQ Pro Therapy transducers (Red Transducer and Yellow Transducer) are also used in the first minutes of sonophoresis treatments. In fact by minimally rising the skin surface temperature, EQ Pro Therapy continuous emission transducers increase dermal capillary vasodilation and cell membrane permeability, therefore allowing transcutaneous absorption of the medication. The acoustic pressure generated by EQ Pro Therapy promotes deep drug diffusion and absorption, therefore optimizing both pharmacokinetics and drug action.

EQ Pro Therapy stable cavitation, acoustic streaming and microstreaming produce distortion and destabilization of cell membranes, inducing autophagy (the body's way of cleaning out damaged cells, in order to regenerate newer, healthier cells). They influence ion fluxes and intracellular activity as well.

Cell membrane destabilization results in an increase in cellular permeability, therefore many molecules travel into the cell, precipitating secondary effects:

• increase in cell membrane permeability
• increase of intracellular calcium (known as second messenger for cell function, including protein synthesis)
• increase mast cell degranulation
• increase histamine and chemotactic factor release by granules from mast cells and circulating platelets (influencing circulation and protein synthesis)

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In summary cell membrane destabilization is thought to enhance the inflammatory response from the inflammatory phase, consequently aiding and speeding up tissue regeneration and repair.

The most important parameters for the generation of mechanical non-thermal effects are:

• ultrasound frequency
• intensity of ultrasound emission
• exposure time

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At high ultrasound frequencies, on the order of the MHz (like in traditional high frequency ultrasound devices), the production of cavitation bubbles becomes more difficult than at low ultrasound frequencies, of the order of the kHz (like with EQultrasound Pro Therapy).

To achieve cavitation with high frequency 1-3 MHz devices, ultrasound intensity must be significantly increased, to ensure that the cohesive forces of interstitial fluids are overcome and voids are created; too high ultrasound intensities can lead to burns and tissues damages. Furthermore histamine is released by the degranulation of mast cells. The rate at which this occurs is proportional to the ultrasound intensity (the higher the ultrasound intensity, the more histamine is released). It is possible to form too much histamine with a high intensity outputs, which could prolong the inflammation instead of stimulating healing.

This is one of the main advantages offered by EQ Pro Therapy low frequency therapy (38 kHz +/-2) versus traditional high frequency ultrasound therapy (1-3 MHz): since EQ Pro Therapy operates at a much lower frequency than traditional high frequency devices, it can safely produce stable cavitation, acoustic streaming and micro-streaming without the need to increase significantly ultrasound intensity.

The acoustic and mechanical effects produced by EQ Pro Therapy increase cellular metabolic activity, cellular permeability, blood micro-circulation, enzymatic activity, tissue oxygenation and remove metabolic debris produced by the injury. All these physiological effects contribute to accelerate healing, reducing edema and pain, and speeding up the inflammatory phase of tissue repair for a faster recovery of the treated areas.