Effects of Deep Muscle Stimulator on the perception of pain and blood flow in homosapiens.
Dr. Michael Laymon
Touro University of Nevada School of Physical Therapy
Interim Report Status
This is an interim report of pilot study data collected examining the effect of a 4 minute treatment of the Deep Muscle Stimulator (DMS Las Vegas, NV) on superficial and deep blood flow and pain perception of the wrist flexors. The pilot study results support further study of this device in relation to promoting superficial and deep blood flow in surrounding tissues.
As physical therapists, one of our main goals is to increase our patient’s quality of life. This can be accomplished in a variety of ways depending on the patient’s symptoms. All patients have different signs and symptoms that must be addressed to reach their goals. One of the most common complaints is pain. Pain is a subjective assessment that is hard to quantify; we attempt to quantify pain using surveys, scales, and algometry measurements. Modalities is a method clinicians use to decrease pain whether it is electrical stimulation, ice, heat, or massage. These are attempts to reduce pain quickly using different methods (Gate theory). We propose the use of a new machine called the deep muscle stimulator (DMS) may show the ability to decrease pain and increase blood flow in a healthy population.
The deep muscle stimulator (DMS) consists of a hollow titanium head with loosely packed granular materials such as diamonds, rubies, copper, garnet, malachite, and carbon. The head is mounted on a handle containing a rotating electrical motor to provide deep rhythmical pressure and percussion. The device is made from stainless steel or titanium, so it is capable of withstanding heavy use by different medical professionals. There are other vibrations—type devices used to help relieve stress or tight muscles. However, these devices do not oscillate at high enough speeds or deliver adequate force to reach the deeper musculoskeletal tissues. Due to this, there is a need for the deep muscle stimulator which provides mechanical vibrations that can reach the deep muscle tissue. The DMS also suggest that it decreases pain and increasing blood flow which we are testing.
Considering the lack of studies performed on the DMS, we have decided to accumulate evidence of similar types of treatments that have been proven to reduce the perception of pain and increase blood flow. We have focused on studies which look at different types of massage techniques (Greskowiak, et. Al., 2012) and other modalities such as the Hand Grip T-Bar (Kim, et. Al, 2012) that incorporate vibration. There is considerable academic literature regarding the effects of continuous and temporal summation has on decreasing the perception of pain following treatment (Nie, 2005; Menard; Kim, et. Al., 2012).
Most of these studies were done using a survey instrument to determine if the treatment decreased the subjects’ pain. One of the most widely accepted methods to quantify pain is the visual analog scale (VAS) which is a continuous line from 0-10. The patient is given a description of the types of pains ranging from 0-10, and they place a mark on the line when asked about the pain they are experiencing. The VAS was used in many of the studies we found Grezeskowiak et al., Menard, Nie et al., Hollins et al., & Adnadjevic et al. While it has always been a challenge for medical professionals to quantify pain and the VAS has good reliability we decided to use an algometry in our study which also displays good reliability.
A pressure algometry is a new device that places a numerical value on the perception of pain threshold (PPT) indicated by the subject. The machine is a small device with a small circular probe with a flat surface which comes into contact with the patient. Force/pressure then applied by an examiner through the machine into the patient. The numerical value which it is recording is a force, and it is measured in newtons (N). The subject then indicates when they feel pain, and the number is recorded. This is now a widely accepted method to detect the PPT from subjects. There are factors to consider when using an algometry such as gender (Chesterton et al., 2003), Inter-examiner and intra-examiner differences (Antonaci et al., 1998) and the actual type of pain being perceived (Michele, 2011). But there has been studies done taking these variables into account, and we can use these studies when calculating our statistics.
The purpose of this study is to examine the effectiveness of the deep muscle stimulator (DMS) on the perception of pain (PPT) on the wrist flexor muscles. We hypothesized that a 4- minute treatment with the DMS on the forearm flexors would decrease pain as measured by an algometry and increase deep blood flow measured by imaging ultrasound and superficial blood flow measured by red laser. The DMS has claimed to increase circulation, decrease pain, increase blood flow, breakup of scar tissue, increase lymphatic flow, reduce lactic acid build-up, increase flexibility, and quicker rehabilitation times. If we can show that the DMS decreases the patient’s PPT and increases blood flow from a 4-minute treatment, we might be able to start considering it for a treatment use for pain.
I. Vibration and Massage
In order to determine how pain is reduced from vibration and massage we need to look at studies which incorporate this into their procedure. Instrument assisted soft tissue mobilization (IASTM) and therapeutic massage are used as a treatment method to decrease pain. The tool for our prospected study provides a similar application of soft tissue mobilization to therapeutic and deep tissue massage. Wang and Keck, 2004 suggest that massage can be used as an intervention on postoperative pain. With 5 minutes of massage there was no reported decrease of pain, but 20 minutes of massage could produce a significant decrease in pain, intensity, and distress (Wand & Keck, 2004). A similar tool was studied on its ability to decrease chronic low back pain with cross friction massage and showed statistical evidence of decreasing pain (Kim, et. Al. 2012). Deep tissue massage has also been shown to decrease pain in chronic low back pain patients (Grześkowiak, et. Al., 2012). Therapeutic massage has also shown the ability to decrease pain and unpleasantness immediately after treatment (Menard, 2015). These studies show that pain algometry is viable way to test pain in combination with IASTM used to reduce pain. In addition, massage is an inexpensive and low-risk procedure rather than vibratory devices which can increase the price.
Another technique that is suggested to reduce pain tolerance is vibration. Hollins, Roy, and Crane, 2003, used a model 4810 Breul and Kjaer minishaker (vibrations of 60 and 230 Hz) to get a desired sensation level. They suggest that vibratory signals interfere with nociception in a graded way and also that this the technique was not a result of merely shifts or interaction (Hollins, Roy, & Crane, 2003). Since the deep muscle stimulator uses these same principles we can say that our study will produce similar decreased pain thresholds. Another study done by, Beinert, Preiss, Huber, and Taube, 2015, suggests that vibration significantly increases pressure pain threshold. Using a handheld vibration device at 100 Hz at the painful site, the authors found that the vibrations exhibit a strong role of afferent inputs (Beinert et al., 2015). In this study each patient received 45 seconds of vibrations with a 15 second break and completed this cycle for 5 minutes. For our study we will try and incorporate these parameters into our design.
Additionally, Kuwahara & Ogawa, 2016, suggests that in order to explain the decreased nociceptive signal we have to consider the Gate Control Theory of Pain.
II. Gate Control Theory of Pain
In order to appreciate how vibration and massage decrease the pain threshold we have to refer to the Gait Control Theory of Pain. There are cells in the substantia gelatinosa that project toward the brain and the T-cells in the dorsal horn. There are large (A-fibers) and small (C- fibers) that when stimulated have either, inhibitory or excitatory affect in the transmission of pain (Katz & Rosenbloom, 2015). The gating mechanism is affected by the activity in these large and small fibers, with the inhibitory transmission (closing the gate) and excitatory transmission (opening the gate) (Katz, et. Al., 2015). Spinal transmission cells activate an action system in the brain allowing the perception of pain to be reduced (Katz, et. Al., 2015). This theory has major clinical implications such as explaining phantom limb pain, reactions to pain, and gives rise to approaches to manage pain (Katz, et. Al., 2015).
III. Pressure Algometry
A hand held device with a 1⁄2 cm round surface area is placed in the area being tested and a pressure measurement is taken which gives how much pressure will produce pain. As patients receive mechanical vibrations and a decrease in nociceptive signal is produced and an algometry may be used to measure the perceived pain. Adnadjevic & Graven-Nielsen, 2014 suggests that pressure pain thresholds can be measured through a biaxial algometry. In addition, they also suggested that linear vibrational stimulation effect on pressure pain perception verified that the vibratory stimulation produced a decrease pain threshold (Adnadjevic & Graven-Nielsen, 2014). Additionally, pressure algometry has shown statistical validity when used as a diagnostic tool to quantify pressure pain thresholds making it the best candidate (Michele, 2011). Pressure algometry has also shown to have good inter- rater and intra-rater reliability which will allow more than one researcher to use the algometry if necessary (Grześkowiak, et. Al., 2012). One finding that should be reviewed with the results are gender differences among algometry results due to a study by Chesterton et al., 2002, finding that the average pressure pain tolerance was higher in males compare to females.
Methods & Procedure
This study included 10 healthy subjects (5 females and 5 males) with no complaints of pain in the upper extremities. Subjects with a history of fractures, surgeries, metal plates, or any recent trauma to the forearm, elbow or upper arm region will be excluded. All participants who are on cardiac medications will be excluded from the study. These medications include diuretics, blood thinners and anti-coagulants. Written informed consent were obtained from each participant prior to inclusion in the study.
The subjects were seated in a chair with their supinated arm rested on a table and elevated at 60-80 degrees of shoulder flexion and 0 degrees elbow flexion for 15 minutes to acclimate to room temperature. The pressure pain threshold (PPT) with the algometer was assessed on the flexors of the forearm. Blood flow was measured by Biopac red laser Doppler for superficial blood flow at the middle finger and deep blood flow via Imaging Ultrasound of the radial artery prior to the application of the Deep muscle stimulator (DMS), two PPT measures were performed approximately 30 seconds apart. Subjects were instructed to say “stop” when a discernible pain is felt, and the experimenter then retracted the algometer and recorded the value of pressure. The DMS was administered in a 6” circular area with the center being where the original PPT was taken. The DMS was rotated clockwise for 2 minutes and counterclockwise for 2 minutes. This treatment was given for 4 minutes then the subject rested for 30 seconds. After the rest repeat blood flow and algometer measurements were taken at the same site. Each session took approximately 30 minutes.
Ten healthy subjects free from upper extremity orthopedic, metabolic, or neurological conditions were recruited. Five male and five female between the ages of 24-29 participated in the pilot study.
Table 1. General characteristic of subjects (n=10)
Abbreviation: SD, standard deviation
Repeated measures T Test was performed with the level of significance set at p≤0.05.
There was statistically significant improvement in pressure pain tolerance, superficial blood flow, and deep blood flow. There was a 25% increase in deep pressure tolerance for pain (31.2 N to 50.7N), a 13% increase in superficial blood flow (146.4 Flux to 165.8 Flux), and greater than two times increase in deep arterial blood flow (127% increase – 5.6 ml/min to 12.7 ml/min).
This pilot data supports an increase in superficial and deep blood flow distal to the area of 4 minute application of the Deep Muscle Stimulator. Pain tolerance to pressure was also significantly improved at the site of application. Improvement in the superficial blood flow indicates that there is not capillary bed congestion of blood flow secondary to application of the devise. Likewise, deep flow increases support a generalized improvement in perfusion throughout the limb distal to the site of application. Application of this modality may have beneficial effects on improving healing of skin and connective tissue injuries distal to the application area. This data also confirms an analgesic effect to the tissues the device is applied.
This study demonstrates the effectiveness of the Deep Muscle Stimulator to decrease pain sensitivity and increased superficial and deep blood flow following a 4 minute application.
Proposed Progression of Project
The project will be expanded to include a larger subject population and expanded demographics. If further analysis demonstrates the same results, the next step is to examine how long the increased circulation and analgesic effects last following application. Then examining the effects with certain health populations such as those with diabetes, circulatory disorders, skin ulcers, etc.
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