Scale to Measure Nighttime Weight Change Kyle Herzog – Team Leader Joe Ferris – BWIG Ben Engel – Communications Eric Printz – BSAC Advisor: Wally F. Block, Professor of Biomedical Engineering Client: Timothy Juergens, M.D., Geriatric psychiatrist/sleep specialist December 10, 20062Table of Contents TABLE OF CONTENTS ..................................................................................................... 2 ABSTRACT........................................................................................................................... 3 MOTIVATION ..................................................................................................................... 4 PROBLEM STATEMENT................................................................................................... 4 CLIENT REQUIREMENTS................................................................................................ 4 BACKGROUND INFORMATION .................................................................................... 5 Correlation between Obesity and Weight Gain Before Bed…………………….…….…………5 Correlation between Obesity and Insomnia………………………………………………………..7 DESIGN ALTERNATIVES.................................................................................................7 Load Cell ................................................................................................................................ 7 Pad Design............................................................................................................................. 10 Tension Meter........................................................................................................................ 11 DESIGN EVALUATIONS................................................................................................. 13 FINAL DESIGN COMPONENTS……………………………………………………….15 Analog/Digital Converter…………………………………………………………………………..15 Amplifier………………………………………………………………………………………………16 Load Cell………………………………………………………………………………………….…..17 Test Stand…………………………………………………………………………………………….18 Data Interpretation………………………………………………………………………………….19 COST ANALYSIS…………………………………………………………………………20 FUTURE WORK................................................................................................................. 21 ETHICAL CONSIDERATIONS…………………………………………………………22 REFERENCES.................................................................................................................... 24 APPENDIX........................................................................................................................... 253Abstract It has been proposed to design a weighing device that can measure weight change of a patient in a hospital bed over the course of a night. A patient’s weight can fluctuate as much as 700 g in one night. Studies recently performed at Yale and the University of Japan have shown a direct connection between sleep and long term weight change. Our client believes that there is a connection between the pattern of this weight change and sleep stage changes. Due to the minute weight changes, the device would have to read at an accuracy of about 0.05 lbs, but the more accurate the device the more useful it will be. The weight of the patient should be recorded every ten to fifteen minutes throughout the night. The device would likely have to support a hospital bed supported by four legs. The device should be capable of being moved between beds with minimal difficulty and without any complex recalibration required. We considered three separate design alternatives: a weighing pad to be placed under the mattress, a load cell placed under each leg of the bed, and a tension meter design. After analyzing each option we decided to proceed with our load cell design. Our prototype consists of a load cell that sends its signal through an amplifier and then to an analog digital converter. This signal is then read by a computer and the weight readings are exported to an excel file using a program that we specially wrote.4Problem Statement For most people, weight fluctuates throughout the day and night. As a result one can lose as much as 700 grams over the course of the night, even if they do not eat or go to the bathroom. Much of this is related to metabolism, as well as water loss. We would like to be able to measure this weight change accurately on people who are in hospital beds. This will require that our device record the patient’s weight every fifteen minutes. The device would likely have to support a hospital bed, which sits on four legs, and read at an accuracy between 0.02- 0.05 lbs. Ideally the device could be moved to a different bed without too much difficulty (one to two hours time) and without complex recalibration. Motivation Tracking weight change over the course of a night may be important from a research perspective. There are a number of potential variables that may affect this weight change, such as medications and sleep stage changes. Another potential use would be to track and eventually predict those at higher risk of developing obesity, correlate with body fat measurements, activity, and assess for metabolic changes when we do things to improve or correct sleep problems. There is popular concern in recent sleep literature regarding various sleep stages, insomnia, and their impact on obesity. Client Requirements One of the device’s important client requirements is that it output weight readings to a computer at chosen time intervals. The user should be able to choose the frequency of readings and have the data values imported to a program that is as universal as possible, such as Microsoft5Excel. This will allow for easy analysis and manipulation of the data. The more accurate the scale, the more useful the readings will be. An accuracy of 0.02 to 0.05 lbs is desired, but a slightly less precise scale would still be very
View Full Document
Unlocking...