Many patients receive ultrasound therapy in the clinic, outpatient ER, or doctor's office yet do not know how or why it works, or doesn't work. This is a general discussion of what is ultrasound and how does ultrasound work.
Ultrasound units operate on production of sound waves that can produce heat in one mode yet in another mode create physiolgical change on a cellular level. Sounds good but what does that mean?
If you take your hands and rub them together very rapidly you will create friction which produces heat. When ultrasound is used on the patient in the clinic on "continuous" mode the same type physiological occurrence is happening, except on a deeper level within the structure being treated such as elbow, low back, leg etc. The ultrasonic energy is moving the cells back and forth deeper inside the tissue and creating heat. From heat flows other therapeutic benefits such as increased blood flow which often reduces pain during the treatment and for some residual or carryover pain relief post treatment.
Most ultrasound machines can also be set on "pulsed" mode which is when the unit is turning off and on automatically. As an example on continuous the ultrasound machine is constantly on and moving molecules but on pulsed it may be on for short periods of time such as on 20% of the time the continuous treatment is. The ultrasound is adminstered to the treatment area for short time period, then turns off and comes back on later for short burst of ultrasonic energy. The "pulsed" mode does not produce heat.
Generally speaking most treatments are applied on "continuous" mode simply because ultrasound treatments are initiated with the desired effects of producing heat within the damaged tissues. Continuous mode is not indicated in acute injury that may have occurred within the past 24 - 48 hours. At that point in time the body is in an inflammatory process and additonal heat is not beneficial to healing, and can actually irritate. During the acute stage "pulsed" mode may be used to increase the physiological responses occuring due to the injury.
After the initial injury, when heat is beneficial, continuous mode is indicated for pain relief. Generally speaking the patient does not "feel the ultrasound" and this is always true on pulsed mode. The ultrasound head needs to be moving at all times on continuous mode as there is a danger of harming the patient if the head, with the crystal inside, is not constantly moving to avoid heat build up in the underlying tissues.