Design ConstraintsProposed SolutionsCircuit BoardConsolidated CircuitryProduct Design Specification:EMG Biofeedback DeviceTeam Members:Design Requirements:Physical and Operational CharacteristicsProduction CharacteristicsMiscellaneousEMG Biofeedback DeviceBME 200/300Final Design Report12-10-03Team Members:Tom Chia Jason EthingtonKim TremlTim RandBrent GeigerClient:Arleigh Birchler, MDiv, BSNAdvisor:John Webster, Ph.D.Professor EmeritusDepartment of Biomedical EngineeringUniversity of Wisconsin - Madison1Abstract The following report outlines a design of an electromyogram (EMG) controlled massaging pad intended for use by a child with lissensephaly. The device was designed using criteria and constraints suggested by a client familiar with lissensephaly. The final design consists of an electrode attachment device, an analog circuit to amplify and process the patient’s EMG signal and a massaging pad to provide positive tactile stimulation to the patient. A prototype circuit was built and tested and the design functions properly. The circuit was constructed on a printed circuit board to consolidate the circuitry, however future work is needed to complete the final printed circuit board design. Problem StatementThe purpose of this project is to design a device that will serve as an EMG biofeedback device to activate a vibrating pad. A child with Lissencephaly will use this device to activate the pad by flexing a muscle in his thigh. The vibrations will provide a pleasurable tactile sensation at his command, providing him some control over his life which he currently lacks. An EMG signal of a chosen magnitude will activate the pad andthe pad will deactivate after a chosen time period.MotivationThe child with Lissencephaly currently has no control over his life. This device will give him a way to take some control. By allowing him to activate the pad on his own the child will be given freedom that he currently lacks. Our device will also allow us to observe whether the child is capable of simple operant conditioning; should the child associate flexing his muscle with activating the massage pad it will demonstrate a capacity for cognitive activity. We would observe this association through a deliberate increase in the flexing of the targeted muscle. This could provide a basis for further learning. The device could be 2modified to give more options to the child. For example, a component of the circuit couldbe added so that the child could also turn the device off with a second flex. This process of learning would serve to improve the quality of the patient’s life LissencephalyLissencephaly is a brain disorder exhibited when the brain fails to correctly develop. Lissencephaly is also referred to as smooth grey matter due to the smooth appearance of the brain in patients with this condition (Figure 1). During development, nerve cells are not able to reach the outer cortex of the brain, which in turn prevents cells from making necessary connections. The deficiency in development also accounts for the lack of ridges normally present [1]. Symptoms of Lissencephaly can vary from case tocase. Some of the common problems experienced aredifficulties eating, loss of bodily control, severe mentalretardation, regular seizures and reoccurring pneumonia.The severity of these symptoms varies greatly. Thelifespan of a person with Lissencephaly is projected ataround two years, but since the disorder is quite rare andprovides few recorded cases the lifespan is difficult togauge [1]. 3Figure 1: (above) A normally developed brain.(below) A brain from a patient with Lissencephaly. Notice the smooth appearance of thisbrain[2]Design ProblemThe EMG biofeedback device needs to detect a proper EMG signal and then activate the massage pad for a predetermined amount of time. There are three major components to the EMG biofeedback device; the EMG electrodes, the EMG amplifier circuit and the massage pad. Either needle or surface electrodes can measure EMG signals. We will be using the less invasive surface electrode. Surface electrodes are often composed of a Ag+/AgCl disk and an adhesive attached to the skin [3]. However, the client has specified that the EMG electrodes need to be reusable. Reusable EMG electrodes are already in use with the child for his apnea monitor. The EMG pads need to be easily attached to the child’s body, reusable, and require minimal training for application. A total of three EMG electrodes will need to be attached to the patient’s body. 4Figure 2: Schematic of chair Figure 3: Patient’s actual chairThe EMG circuit needs to detect a proper EMG signal and respond by activating the massage pad. A proper EMG signal is defined as a voluntary muscle contraction. This patient will occasionally have seizures which result in involuntary muscle contractions. Therefore, the device will need to distinguish between voluntary and involuntary muscle contractions. Once a proper EMG signal is detected the massage pad will be activated by a timer for a predetermined amount of time. The final component in the EMG biofeedback device is a massaging pad. The padis the device that will deliver the pleasurable stimulus to the patient. There is a wealth of small vibrating devices available through retail, ranging in function from full back massage devices that fit inside a chair to simple massage pad motors. The massage pad used in our biofeedback device must fit the unique shape and size of the patient’s chair. Figure 2 is a schematic of the chair with its dimensions and figure 3 is an actual picture ofthe chair.More detailed discussion of each component in the EMG biofeedback device is found in the latter parts of this report. Overall, the entire device must be safe and reliable for years of use by the child and his caretakers. The controls on the device also need to beeasy to learn and operate. Finally, throughout the design process the patient’s confidentiality must be maintained. At no time can the patient’s name, personal information, and/or pictures of the patient be released to the public. Design ConstraintsDesigning our device specifically for this patient introduced a number of design constraints. The first constraint was that our device must not interfere with any of the pre-5existing equipment already in use with the patient. This includes his apnea monitor, feeding tube, and oxygen tank. The EMG amplifier designed for this project also needs to be designed for the patient’s
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