Redesigning the Current Electronic Stethoscope Design - Research Paper Example

Electronic Stethoscope al Affiliation Main Objective The project aims at redesigning the current electronic stethoscope design to fit into the growing technological advancement in terms of size and efficiency. Objectives · including an electronic wireless system for sound transmission · Adding a second microphone to the current electronic stethoscope · Adding a headphone option on the stethoscope. Redesigning of the stethoscope’s case to suit the redesigned device Reducing the power consumption rates of the device The objectives are to be implemented based on the client’s requirements since he has adequate experience with the traditional stethoscope. Introduction Abstract A stethoscope is medical equipment used for testing the heartbeats and the lung sound. The equipment is mainly mechanical in nature and the current electronic devices are not used due to the large size and sound variation. This projects aims at redesigning the electronic stethoscope by reducing its size and improving its sound system. The stethoscope has been in use for the last 200 years, but very few changes have been made on the traditional stethoscope. The traditional stethoscope is the stethoscope that relies on the original stethoscope design, which is common in medical practice today. There are several attempts to develop effective high tech stethoscope given the advancement in medical technology. The stethoscope remains one of the least advanced equipment in the doctor’s chambers. This is because some of the developed stethoscopes are expensive or face regular breakdowns hence ineffective. To enhance technological innovation on this instrument medical instruments the electrical and electronic engineers have chipped in to innovate a modern electronic stethoscope to replace the traditional diaphragm type stethoscope. This project was developed on clients request for a complete redesign on the current electronic stethoscope. The clients request that the design should comprise a receiver box, speakers, wireless microphones and a headphone jack. The microphone signals are sent via a quad amplifier. The amplifier filters the signal and implements and initial gain (A) of 3. The mixer receives the two signals which enable the user to choose the microphone of preference for the respective sound quality adjustments. The signal is then passed to another switch providing interactive user ability mode of output between the headphone and speaker. The complete stethoscope is then printed on the board to suit the needs of different users. Problem Statement The current electronic stethoscopes are generally designed for a one time user and are uncomfortable for doctors if used for periods of time. Stethoscopes are the main medical equipment for Anesthesiologists since they have to analyze breath and heart sounds when handling anesthesia cases. The electronic stethoscope makes use of a microphone and speaker system, but it is extremely large for practical uses resulting from large power system. This brings an implication of the need to innovate an appropriate power system. The stethoscope must be redesigned to allow for dual microphone capabilities. Stethoscope Background. The stethoscope is a french physician innovation ‘Rene Theophile’ in 1886 as he was doing an examination on an obese patient. The first stethoscope model was just a wooden tube. The model has evolved over the years into the current stethoscope after undergoing a series of modifications such as an addition of earpiece, and development of the combined chest and diaphragm bell. Currently, the most common stethoscope is the Littman Stethoscopes designed and patented by Doctor David Littman. These stethoscopes are lighter and consist of a single tube that serves to improve the acoustic technology. This project expounds on the design of the current stethoscope comprising of a chest piece which is made up of a shallow piece with the shape of the bell, and a stiff diaphragm. These two pieces are then connected to the earpieces by use of a flexible tube. The bell and the diaphragm are meant to pick low and high frequency sounds respectively. These pieces amplify body vibrations when the chest piece is placed on the patients’ skin. These vibrations are transferred to the listener’s ears through the connecting tube. Generally, minimal changes have been made on the stethoscope’s design since its invention. This is accredited to its perfect functionality. The current stethoscope model faces few problems which should be adjusted efficiently. The user cannot adjust the volume of the stethoscope and depends mainly on the effectiveness of the acoustic sound. This implies sound amplification factor is highly omitted in the model. The earpieces of the stethoscope are uncomfortable to the user. These setbacks have been solved by use of modern technology through the introduction of advanced electronic stethoscope. Current Methods The current stethoscopes are mainly electronic in nature. The current electronic stethoscope was developed in 1961 by Amplivox cooperation. The stethoscope was mainly meant for academic purposes due to its large size. The doctors returned to the use of the original stethoscope since the electronic one did not produce the sound required for examination. It produced varying sounds and it size was ambiguous. Several companies have managed to make several improvements on the stethoscopes sound systems like the transducers, gain amplifiers and the filters. The use of the electronic stethoscope is not common among the medical practitioners as a result of sound interference from the electronic components. The devices are quite sensitive to the surrounding noise which overpowers that of the lungs and heart. The traditional stethoscopes are effective in medical practice but quite ineffective in training since they are limited to one listener. Their sound system is also limited since it cannot be amplified. The electronic stethoscopes are effective in teaching environments but are limited by the high cost. The current stethoscopes have a single microphone and require various adjustments for multiple uses. The stethoscope’s receiver is made up of sensors which receive the body vibrations and covert those vibrations to electrical signals. The electrical signals are converted to sound signals through amplification and filtration processes. The electronic stethoscope is an electronic device used for medical applications hence the project is completely electronic in nature. The stethoscope uses sensors/ transducers, amplifiers, filters, speakers, microphones and headphones which are designed using the basics of electronic and electrical engineering. The process of reducing power consumption of the current electronic stethoscope involves a critical electrical analysis. Design Implementation The design of an efficient portable electronic stethoscope was complimented within a period of one month. This was done based on the prototype designed on the same project. The stethoscope design was broken up into three parts which include: the stethoscope Head made up of the receiver system, the microphone coupling system made up of capacitors and finally the sound output system comprised of the amplifiers, filters, speakers and headphones. The design implementation process was based on the current stethoscope models with the inclusion of the new improvements on the design. Figure 1: General block setup for current design showing three major design components: initial sound pick-up, conversion of acoustic sound to electrical signal, and amplification, filtration, and audio sound of the signal Image Courtesy of: Spring 2011 Stethoscope Team Figure 2: Current electronic stethoscope circuit diagram with microphone input located on the left and audio outputs on the right Image Courtesy of: Spring 2011 Stethoscope Team Activities Schedule The implementation process was broken down in as scheduled in the table below. Table: Implementation Mini-Schedule Week Activity 1 Designing of the receiver components 2 Designing of sound conversion system 3 Designing the output system 4 Designing the case (cover) of the stethoscope Figure3: Schematic diagram of the Redesigned Stethoscope. Microphone The microphone used for the implementation of the project was the MicroElectrical-Mechanical microphone. The microphone is small enough to accommodate the need of a portable electronic stethoscope. The microphone is also electrically driven solving the power issue. The microphone was mounted on a 15mm2 circuit board. The microphone is composed of an amplifier and an impedance converter. These components enable the microphone to transmit digital sound signal recorded from the microphone’s head. The head of the microphone faces via an opening on the circuit boards bottom, and the body is on the top. These devices are common in mobile devices and headsets of the Bluetooth as a result of the small size. The following aspects were of consideration during the design of the microphone: Cost, feasibility, compatibility in the medical practice, size and efficiency. In general MEMs was used in the project since it was the most viable microphone after considering all aspects of an effective design. Wireless Transmission The wireless system is meant to transfer audio signals from the receiver system to the output systems. The wireless device used is the TI’s Pure Path wireless system. The system passes an uncompressed audio digital signal through a link with very high radio frequencies. The system was mainly designed for transmission of sounds implying that the quality of its output is quite high. The system is also available in development kits, which make its easy implement. The kit has rechargeable batteries with a battery lifetime of twenty hours. Amplifiers The main purpose of the amplifier is to increase the gain of the sound output from the receiver. The stethoscope uses two amplifiers for the speaker and the headphone. Class AB amplifiers were used for the implementation of the project hence improving feasibility of the project. The system however requires a heat sink since the amplifiers decapitates heat as a result of the low peak efficiencies (78.5%). This is an implication for the need of a large receiver box which accommodates the large number of heat sinks. The result for using class AB amplifier is that it retains the analog nature of the circuit which simplifies the design. The design aspects considered when selecting the amplifier were: Cost, feasibility, compatibility in the medical practice, size and efficiency. In general Class A-B amplifier was used in the project since it was the most viable microphone after considering all aspects of an effective design. Conclusion The implementation of the design was successful since most the requirements from the client were achieved. The design was also cost effective and more feasible when compared with the original electronic stethoscope. The stethoscope functioned as anticipated during the redesigning process. Power consumption and the size of the design were minimized efficiently to meet the client’s specifications. References Birrenkott, D., Wendorff, B., Ness, J., & Durante, C. (2011). Heart and Breath Sounds Amplifier. Madison: University of Wisconsin-Madison Department of Biomedical Engineering. Grenier, M.-C., Gagnon, K., Genest Jr., J., Durand, J., Durand, L.-G. (1998). Clinical Comparison of Acoustic and Electronic Stethoscopes and Design of a New Electronic Stethoscope. The American Journal of Cardiology, pp. 653-656. Griffiths, D. J. (2008, September 26). Development of Ionic Polymer Metallic Composites as Sensors. Retrieved (26th March 2014) from: http://scholar.lib.vt.edu/theses/available/etd-11122008-093649/unrestricted/David_J_Griffiths_MSME_Thesis.pdf Lambe, M. (2009, October 27). How Does the Stethoscope work. Retrieved (26th March 2014) from: http://whyzz.com/how-does-a-stethoscope-work Leyden, J. (2001, May/June). The Chance Invention that Changed Medicine. Saturday Evening Post, pp. 46-73. Standris Medical Supply, Inc. (2011). History of Stethoscopes. Retrieved October 23, 2011, from Standris Medical Supply, Inc.: http://www.standris.com/education_history.cfm Appendix Appendix A Table 1: Work Schedule Activities Feb1 Feb2 Feb3 Feb4 Feb6 Feb7 Feb8 Feb9 Feb10 Feb 11 Feb b12 Feb 13 Feb13 Feb14 Feb 15 Designing and implementation of input system Designing and Implementation of Conversion System Designing and Implementation of the Output System Construction of the Case Assembly of the Components Appendix B: Gain Equation Figure3: Gain amplification the circuit diagram Appendix C: Sallen-Key Low pass filter equation and circuit Figure4: Sallen-Key Low Pass Filter Appendix D: Final Design Circuit Diagram Figure 5: Final Design Circuit Read More