Scale to Measure Nighttime Weight Change Joe Ferris – BWIG Kyle Herzog – Team Leader Ben Engel – Communicator Eric Printz – BSAC Client: Timothy Juergens, M.D. Advisor: Professor Wally F. Block, PhD

Presentation Overview Problem Statement Problem Statement Background Information Background Information Client Requirements Client Requirements Design Alternatives Design Alternatives Design Matrix Design Matrix Future Work Future Work

Problem Statement Device to measure weight changes while asleep Device to measure weight changes while asleep Weight fluctuates throughout the night (700 g) Weight fluctuates throughout the night (700 g) Sleep stage changes and amount of sleep may affect these changes Sleep stage changes and amount of sleep may affect these changes Pattern of weight loss may have an effect on obesity Pattern of weight loss may have an effect on obesity Very minute changes Very minute changes

Background Information Recent study proved long term connection between weight gain in patients and weight change over course of night (2) Recent study proved long term connection between weight gain in patients and weight change over course of night (2) Yale School of Medicine study has showed a connection between insomnia and obesity (1) Yale School of Medicine study has showed a connection between insomnia and obesity (1) Client hypothesis: Weight loss rate varies with sleep stage Client hypothesis: Weight loss rate varies with sleep stage (1) Horvath, Cell Metabolism. April 2005 (1) Horvath, Cell Metabolism. April 2005 (2) Tanaka, Experimental Biology and Medicine (2) Tanaka, Experimental Biology and Medicine

Client Requirements Accurate to 0.05 lbs Accurate to 0.05 lbs No discomfort to patient No discomfort to patient Quick (1-2 hours) transfer time between beds Quick (1-2 hours) transfer time between beds Capable of handling 300 lb patient Capable of handling 300 lb patient Price range of $300 - $500 Price range of $300 - $500 Provide digital readout of data to computer software, preferably Microsoft Excel Provide digital readout of data to computer software, preferably Microsoft Excel

Load Cell Design Resistance proportional to the force subjected to the load cell Resistance proportional to the force subjected to the load cell Using an amplifier and A/D converter the load cell connects to a computer’s serial port Using an amplifier and A/D converter the load cell connects to a computer’s serial port

Load Cell Design Advantages Advantages No discomfort to patient No discomfort to patient Accurate (0.02% of the full load) Accurate (0.02% of the full load) Disadvantages Disadvantages Expensive ($350 for a load cell) Expensive ($350 for a load cell) Portability Portability

Weighing Pad Design A weighing pad is a thin scale with a large surface area A weighing pad is a thin scale with a large surface area Weighing pad placed under the mattress Weighing pad placed under the mattress Wires rerouted from the LCD screen on the weighing pad to a computer parallel port Wires rerouted from the LCD screen on the weighing pad to a computer parallel port Data received through parallel port would be recorded and interpreted using computer software Data received through parallel port would be recorded and interpreted using computer software

Weighing Pad Design Advantages Advantages Easy to move from bed to bed Easy to move from bed to bed Placement under mattress reduces load Placement under mattress reduces load Designed for very large loads Designed for very large loads Disadvantages Disadvantages Not accurate enough Not accurate enough Pad smaller than mattress Pad smaller than mattress Patient discomfort Patient discomfort

Tension Meter Design Digitally measures tension in cable Digitally measures tension in cable Cables attached to platform raised off another platform Cables attached to platform raised off another platform Four tension meters in unison interfaced to computer Four tension meters in unison interfaced to computer Data from meter interpreted by software Data from meter interpreted by software

Tension Meter Advantages Advantages Large maximum load Large maximum load Automatic calibration Automatic calibration No extra discomfort to patient No extra discomfort to patient Disadvantages Disadvantages Cost Cost Bulkiness may affect portability Bulkiness may affect portability

Design Matrix Load CellBed PadTension Meter Cost Portability 351 Accuracy 513 Complexity 351 Patient Comfort 515 Total

Future Work Build amplifier circuit Build amplifier circuit Load cell ~> Amplifier ~> ADC ~> Computer Load cell ~> Amplifier ~> ADC ~> Computer Calibrate and test single load cell Calibrate and test single load cell Purchase four load cells with adequate accuracy Purchase four load cells with adequate accuracy Combine four load cell readings to create a single accurate weight reading Combine four load cell readings to create a single accurate weight reading

Questions?