Engineering World Health: Aspirator Lucas Vitzthum, Team Leader Nick Harrison, Communications Tyler Lark, BSAC Fan Wu, BWIG BME 201 Department of Biomedical Engineering University of Wisconsin-Madison March 11, 2007 Client John Webster, Ph.D, Professor Department of Biomedical Engineering Advisor Paul Thompson, Ph.D Boumatic Inc.2Abstract Medical aspirators are suction devices used to remove mucous and other bodily fluids from a patient. Many developing world hospitals do not possess aspirators because they can not afford or repair the current devices on the market. The goal of this design is to create a less expensive, locally repairable, and less power dependant alternative to current medical aspirators, that can be used by developing world hospitals.3Table of Contents Page Abstract 2 Table of Contents 3 Problem Statement 4 Background Information 4-5 Current Devices 5-6 Design Constraints 6-7 Design 1: Water Hour Glass 7-9 Design 2: Mechanical Foot Pump 9-11 Design 3: Electric Vacuum Pump 11-13 Design Matrix 13-15 Future Work 15-16 References 16-17 Appendix A: PDS 18-194Problem Statement Engineering World Health (EWH), a non-profit organization through Duke University, has asked for help in designing an inexpensive medical aspirator that can be built and repaired from locally available parts and expertise for developing world hospitals. Furthermore, the device must be able to function semi-autonomously of electricity since a constant electric power supply will not always be available. Developing hospitals will likely be able to afford only one aspirator, so the design must function under the broadest range of applications possible. Further research into current medical aspirators gave a basis to create further design constraints including pressure ranges and flow rates. Ultimately, EWH requires an aspirator design that can be built completely from locally available resources that will meet all the relevant criteria for functioning in a developing world hospital. Background Information Aspirating equipment can be found in almost any hospital, ambulance, or dental clinic in the United States. A medical aspirator is simply a suction device used to remove mucous, blood, or other bodily fluids from a patient (Figure 1). The apparatus will generally include disposable suction tips and a removable collection receptacle. This device is a necessary tool in dental practice, liposuction and most surgical procedures. Depending on their exact function, aspirators are generally powered by 120V AC outlets, batteries, or a combination of the two. The size and portability of the device Figure 1: Tip of surgical aspirator. Source: http://www.valleylabeducation.org/esself/Pages/esself23.html5are also determined by its application. Sizes can range from 11.4 lb, battery powered hand held devices to 70 lb stationary surgical units (Allied Healthcare Products, Inc 2005). Aspirators currently on the market are designed for use in modern, state of the art medical environments. Differences in modern and developing hospitals render these models ineffective for use in third world countries. Third world hospital conditions are radically different from their modern American counterparts. Electricity is spotty at best for developing world hospitals and therefore equipment cannot depend on a constant supply of AC electric power. Trained medical professionals are in short supply, requiring devices to have the simplest user interface possible. Limited space is another concern, as most rooms are overcrowded with patients, staff, and equipment. (Hill D 2005) Current Devices There are many medical aspirators on the market today with a wide variety of functions. In the $500-600 price range, Gomco® provides a line of portable aspirators (Models G180, 405 & 300) that use diaphragm compressors to create vacuum ranges from 0-600 mmHg and flow rates of 30 liters per minute (lpm). Dimensioned at 12x9x12 in., these devices weigh around 14.5 lbs. Specialized stationary aspirators are available for uterine, thoracic drainage, endocervical and dental operations. Most are powered via 120V AC current and range in weight from 50-70 lbs. Thoracic and thermotic drainage pumps operate under low pressure and low flow conditions (0-50 cm H20, 2-3 lpm) to regulate drainage levels in post-operative care. Endocervical aspiration alternatively6requires high pressure ranges (600 mmHg) and high flow rates (20-30 lpm) for brief intermittent use. (Allied Healthcare Products, Inc 2005) All of these designs, however, are inaccessible to a developing world hospital for several reasons. The most obvious limitation of these devices is their price; even the cheapest models exceed EWH’s projected 100 dollar budget. In addition, the specialization of current devices provides another budgeting concern. Most aspirators on the market are designed for a very specific function. A hospital that can only afford a single aspirator would need the broadest range of applications possible. Finally, these devices cannot be repaired with locally available parts and expertise. Advanced circuitry and specially manufactured parts render these devices irreparable in developing world hospitals. Design Constraints Engineering World Health provided only a couple of constraints to follow and left the rest of the design quite open-ended, creating the need to establish additional guidelines. The biggest focus of the aspirator design is that it needs to be constructed entirely from locally available materials in third world countries. These materials can include anything already on hand in the hospitals, as well as anything that can be obtained from the surrounding environment, such as car batteries, simple motors, and tubing. The design must include autoclavable suction tips for easy sterilization. The final goal of the semester is to produce a working prototype for fewer than 100 dollars, as specified by EWH. Since the apparatus will be used in a hospital setting, the final7product must be safe for sterile use in the operating room. The final device should not rely solely on electrical power, due to its inconsistent availability in third world countries In addition to these constraints, new ones were created relating to the vacuum pressure range
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