KINESIOLOGY final paper
OPTIMIZING THERMAL ULTRASOUND 1 Ultrasound: Are Aquaflex Gel Pads Equally Effective as Gel Alone for Achieving Increased Tissue Temperature within Optimal Parameters? Texas A&M University – Corpus Christi Clinical Question OPTIMIZING THERMAL ULTRASOUND 2 When applying therapeutic ultrasound within optimal parameters, is using an aquaflex gel pad as a medium equally effective as using gel alone for achieving increased tissue temperature? P Young adults with no edema present or injury in prior 6 months at la teral posterior ankle I Thermal therapeutic ultrasound with gel only as the medium C Aquaflex gel pad O Achieve vigorous heating for increasing joint ROM through effective stretching Thermal ultrasound is a deep -heating modality that can be used for therapeutic purposes including pain control, reducing chronic edema, reducing muscle spasms, releasing trigger points, stretching collagenous tissue and increasing joint range of motion (Rubley & Touton, 2009; Bishop, Draper, Knight, Feland, & Eggett, 2004 ). In order for any therapeutic effects to be achieved however, effective heating of the target tissue must take place. Therefore, it is important to investigate and compare the methods of applying ultrasound through gel alone or with an aquaflex gel pad b ecause if using a gel pad as a medium does not have the potential to produce the same vigorous heating as ultrasonic gel alone it is highly inappropriate to continue using this method in the clinical setting. According to Rubley and Touton (2009), previou sly, studies on thermal ultrasound have generally focused on the deep -heating aspect independently of method; but as the study of therapeutic modalities continue s to progress, it is necessary to presently focus on what specific aspects influence the effect iveness of deep -tissue heating received from therapeutic thermal ultrasound. Before the outcomes of using gel alone compared to using an aquaflex gel pad as a medium can be understood, it is relative to discuss the other main variables that have influence as well which are frequency, intensity, and treatment duration. These factors can predict the level OPTIMIZING THERMAL ULTRASOUND 3 of heating the target tissue attains. 1 C is mild, 2 -3C is moderate and >4 C is vigorous heating (Rubley & Touton, 2009). After establishing the optimal pa rameters for applying therapeutic ultrasound, the question, “Is using an aquaflex gel pad as a medium equally effective as gel alone for achieving increased tissue temperature?” can be answered. Bishop et al. (2004) report s that gel pads transmit 27% more ultrasound energy, which theoretically should lead to a greater increase in tissue temperature. They used 18 college students from 19 -27 years old to test this theory. The 13 women and 5 men had no edema or injury present at their lateral posterior ankle for the previous 6 months; the frequency was 3 MHz with a 1.0 W/cm 2 intensity and a treatment duration of 10 minutes while moving the head at a speed of 4cm/s . Rubley and Touton (2009) also reported multiple studies set up with the same parameters for test ing vigorous heating. This is most likely due to the known ultrasound chart that calculates the application of the heat, establishing these parameters as optimal for effectively achieving vigorous hea ting of the tissue surrounding the ankle . In the study performed by Bishop et al. (2004) the tissue temperature was measured every 30 seconds directly through a catheter inserted halfway between the lateral malleolus and the Achilles tendon while the patient laid prone. They chose to use a 3 MHz frequency beca use the aquaflex gel pad has optimal transmission at < 2.5 cm, which corres ponds with superficial tissue. Thus using an aquaflex gel pad with a 1 MHz frequency is inappropriate and ineffective. It can be inferred t hey chose to use a 1.0 W/cm 2 frequency in order to have the ability to perform a 10 minute treatment without ov erheating the tissue. In fact, Rubley and Touton (2009) report patients commonly reported discomfort at 41 C, likely due to the fact the general baseline for tissue temperature is accepte d at 36 C thus making the discomfort usually seen once heating passes the vigorous level of 4 C. The effective radiating area (ERA) was 4 cm 2, therefore the OPTIMIZING THERMAL ULTRASOUND 4 treatment area could cover a maximum of twice the ERA or 8 cm 2. Bishop et al. (2004) recommend usin g a 3:1 beam nonuniformity ratio and a metronome to pace movement at 4 cm/s. It is important to note studying vigorous heating for achieving increased tissue temperature was chosen because that is where the stretching window of 3 minutes for collagenous ti ssue leading to an increase in joint range of motion (ROM) can be observed optimally. Rubley and Touton (2009) point out that different methods can influence heating effects differently. In the study performed by Bishop et al. (2004) using ultrasonic gel alone produced the greatest increase in tissue temperature, however there was not a significance difference between the increased tissue temperature observed from using gel alone or using an aquaflex gel pad with a layer of gel on the top and the bottom of the pad as a medium. Although there was a significant difference for increasing tissue temperature when using a gel pad with a layer of gel on the top only and placing the gel pad itself directly on the skin; 8 out of the 18 patients also reported discomf ort with the later medium (Bishop et al., 2004) possibly resulting from air pockets which can produce spikes in intensity from the energy not be completely absorbed. Ultimately, the outcome saw using aquaflex gel pads as a medium for applying thermal ultr asound was equally effective as using gel alone only if there was ultrasound gel coating the top and bottom side s to the pad. Both methods yielded > 4 C increased tissue temperature which achieves vigorous heating (Bishop et al., 2004). Rubley and Touton ( 2009) suggest to observe optimal therapeutic effects of thermal ultrasound, it is in the best interest of the clinician to be familiar with not only the me thods of application and appropriate parameters, but the ultrasound unit as well. In conclusion , to maximize treatment effectiveness it is important to know the ERA of the unit and to not treat an area greater than twice that size. Correctly calculate what frequency OPTIMIZING THERMAL ULTRASOUND 5 and intensity are being used , specific for the target tissue, in order to stop treatment prior to or once an increase of 4 C is achieved for vigorous heating; also be familiar with the stretching window of 3 minutes post -treatment for use with increasing joint ROM. The speed of the head should be no more than 4 cm/s. According to Rubley and To uton (2009) high water content will also contribute to maximizing energy transmission and will minimize the absorption. This is important because this is likely the reason coating an aquaflex gel pad on both sides with ultrasound gel provides the same effe ctiveness for increasing tissue temperature as gel alone ; when the skin is in contact with the ge l it sets up the optimal therapeutic window referred to in the Arndt -Schultz Principle and Law of Grotthus -Daper which overall state the energy cannot be too g reat for the tissue otherwise it will be destructive but also, if the energy is absorbed too soon the treatment is inadequate and no therapeutic effects will be seen. It is the clinician’s choice to use an aquaflex gel pad or gel alone, although using an a quaflex gel pad alone may not be t he best method of application. W hen used in combination with ultrasonic gel on the top and bottom sides, both methods are equally effective for increasing tissue temperature. References OPTIMIZING THERMAL ULTRASOUND 6 Bishop, S., Draper, D. O., Knight, K. L., Feland, B., & Eggett, D. (2004). Human tissue – temperature rise during ultrasound treatments with the a quaflex gel pad. Journal of Athletic Training, 39(2), 126 -131. Rubley, M. D., & Touton, T. M. (2009). Thermal u ltrasound: It’s more than power and time. Athletic Training Today, 14(1), 5-8.