amy rosenthal, nicole typaldos, emily jaeger mentor: dr. frank cp yin
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New Minimally-Invasive Bed-Ridden Patient Weighing SystemAmy Rosenthal, Nicole Typaldos, Emily Jaeger
Mentor: Dr. Frank CP Yin
BackgroundPatient’s weight is critical to care
Uncomfortable for patients to be weighedDifficult and time consuming for nurses to
move patientsNurses often estimate weight to avoid the
hassle May become unsafe to weigh certain patients
Obesity has increased to over 35% of the population1
1. United States. Center for Disease Control and Prevention. Department of Health and Human Services. Prevalence of Obesity in the United States, 2009-2010. By Cynthia L. Ogden, Margaret D. Carroll, Brian K. Kit, and Katherine M. Flegal. Vol. 83. Hyattsville, MD: National Center for Health and Statistics, 2012. CDC. Web. 23 Sept. 2012.
ProblemPatients can be lifted
UncomfortableUnsafe for patient and nurseDifficultComplicated
Scale built into bedNurses forget to tarePoor repeatabilityNurses are expected to do calculation
Bed can be weighedDifficult to move the bedUncomfortable for patient to moveLarge weight of the bed must be subtracted off causing
less accuracy
ScopeDesign a device for weighing bedridden patients within 0.23 kg
(0.5 lbs) and with minimal movement of patient to avoid the discomfort for patients and hassle for nurses.
A single user with no additional training will be able to operate the device and determine the weight of the patient within 5 minutes of seeking the information so weighing can be done efficiently without taking the current 15-20 minute standard.
The device design will not interfere with normal patient care. Adults and obese patients weighing 22.7 kg to 453.6 kg (50 lbs to
1000 lbs) should be able to remain comfortable while weight is monitored.
Some automatic capabilities will be added to ease continual patient weight monitoring including an automatic readout for use in hospitals.
The device will cost a maximum of $10,000.
Current PatentsAttached to the bed
Design raises bed on a leg attached to a force transducer that takes weight1
1. Neuman, Eli. Weighting Device for Bedridden Patients. Tedea-Huntleigh Intl. Ltd., assaignee Patent 5747745. 05 May 1998
Current PatentsMobile scale
Design slides under hospital bed and then weighs both bed and patient and then the bed weight is subtracted1
Design has scale wheeled against patient bed, but still requires moving patient2
Design goes under bed mattress to give reading3
1. Ashpes, Adam T., Rynd, Richard. Mobile Hospital Bed Scale. EZE Weigh, LLC., assignee. Patent 5990423. 23 Nov. 1999
2. Stultz, Frederick L., and Clark, George C. Scale for Weighing Hospital Patients in their Horizontal Position. Acme Sclae Company, assignee. Patent 4006789. 08 Feb 1997
3. Hasty, Byron E. and Carbona, John A. Portable Scale. CH Administration Inc., assginee. Patent 5393935. 28 Feb. 1995.
Current PatentsVeterinary scales
Design pulls cables taught when table is in lowest position, letting force transducer measure weight1
Design has a platform suspended at four corners with tensile load cells that give signal proportional to force2
1.Rosenberg, Philip M., and Rosenberg, Alexander J. Veterinary Examination Table. Animal Veterinary Products, Inc.,
assignee. Patent RE32052. 24 Dec. 1985. 2. Schneider, H. Allen. Animal Scale. Weigh Right Electronic Systems, Inc., assignee. Patent
4286679. 01 Sept. 1981
Stryker Hospital BedsBariatric Hospital Beds
Model: Bari 10A In bed scale standard with 453.6 kg (1000lb) range
Critical Care BedsModels: InTouch, Epic II
Integrated scale only comes standard in InTouch model Maximum weight capacity of only 228 kg (500lb)
Med/Surge BedsModels: S3, GoBed II
Integrated one-touch scale optional in both models Ability to weigh patient in any position
Stryker. http://www.stryker.com/en-us/products/PatientHandlingEMSandEvacuationEquipment/Beds/index.htm
Hill-Rom Hospital BedsBariatric Beds
TriFlex II-Optional In-bed scale Maximum capacity 453.6 kg (1000 lb) capacity
Excel Care ES – In-bed scale standard Accuracy of 1% of patient weight when sleep deck in
supine position Maximum capacity of 453.6 kg (1000 lb) capacity
TotalCare Bariatric Plus – Integrated scale standard Accuracy of 1% of patient weight up to 181.4 kg (400
lb) Functional up to 227 kg (500 lb)
Hill-Rom. http://www2.hill-rom.com/usa/index.asp
Hill-Rom Hospital BedsNon-Bariatric Beds
VersaCare – In-bed scale standard Accuracy of 1% of patient’s weight, even with head
elevatedCareAssist ES – optional integrated scale
Accuracy within 1 kg (2.2 lb) or 1.1% of patient’s weight, whichever is greater
Repeatability is within 2% of patient’s weight Functional up to 227 kg (500 lb)
Hill-Rom. http://www2.hill-rom.com/usa/index.asp
Hoyer Lift ScalesVariety of models with capacities ranging
around 500 to 700 lbsNeed to buy the lift and the scale separatelyLift slings can be either a chair or a stretcher
liftCommonly usedPortable
Design Specifications: ForceRange: 22.68 kg 453.59 kg (50 lbs to 1000
lbs)Sensitivity: 0.23 kg (0.5 lbs)Repeatability: Variance of less than 0.25 kgForce transducers linear over 44 N to 5000 N
Design Specification: SafetyShockproofWaterproofCan be sterilizedCurrent leakage of less that 100 microamp
Design Specifications: DeviceSize: fit within normal bed dimensions (91 x 213 cm)Portable: May be carried by a single nurse, less than 35lbsDigital readout of weightOption to remove or add the object’s weight (i.e. to
account for removal or addition blankets)Interface with computer or standalone deviceDisplay output in units of kg or lbsEfficient: less than 5 minutes to operate and single output
for easy readingMade for adults and obese patientsPower source: 120 V AC or convert to DCTemperature range: Perform in 10°C to 37°C (50°F to 100°F)
Design SpecificationsMinimal movement of patientNo change to patient’s comfort
Load Cell EquationsConverts force into an electrical signal.
Force deforms a strain gauge which measures the strain as an electrical signal, as a strain causes a change in the electrical resistance
Strain gauge in form of Wheatstone bridge
€
Rx =R2
R1
⋅ R3
Load Cell Equation Electrical signal output must be amplified by
instrumentation amplifier
€
VoutV2 −V1
= 1+2R1
Rgain
⎛
⎝ ⎜ ⎜
⎞
⎠ ⎟ ⎟R3
Rgain
Mass EquationWeight = mass x acceleration due to gravityg = 9.81 m/s2 = acceleration due to gravity
€
750N
9.81ms2
= 76.4kg
Freitag, Elke, et al. "Determination of body weight and height for critically ill patients admitted to the intensive care unit: A quality improvement project." Australian Critical Care 23 (2010): 197-207.
Current Nurse Calculations for Weight by Bed
Team OrganizationAmy Nicole Emily
First Presentation Second Presentation Third Presentation
Computer Programming
Hospital Contact Client Contact
Designs Electrical Component Mechanical Aspect
1 2 3 4 5 6 7 8 9 10 11 12 13 14Initial Process
Background Research
Literature Patents
Social Impact
Interviews Problem Definition
Project Scope
Specifications
Metrics Concept Generation
Brainstorming
Comination Table
Design Alternatives
Project Choice
Design Requirements
DesignSafe
Project Development
Draft Due Timeline to
work on project
Course Assignments 1st 2nd 3rd 4th 5th 6th 7th 8th 9th 10th 11th
12th
13th 14th 15th
Preliminary Report
Preliminary Presentation
Progress Report Progress
Presentation Final Report
Final Presentation Design Webpage
Poster Presentation Final Due Date
Initial Draft
Timeline to work on project
Due Dates
Questions?