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jPulseOx Design Specifications

Draft design specification v1.0 - updated 30/11/05

Overview

The jPulseOx will be a standalone, handheld, battery-powered pulse oximeter for use in operating theatres and other hospital areas in developing countries. Its primary function will be to monitor an anaesthetised patient’s oxygen saturation and heart rate and so assist in the safe provision of anaesthesia by suitably trained medical personal.

It is expected that the jPulseOx may also be used in:

  • Recovery/Post-anaesthesia care units (PACU)
  • Intensive care and high dependency units
  • Emergency departments

 

As a secondary function, the same design will be capable of operating as a pulse oximeter simulator for use in training situations in Western countries. The device will be software factory-locked to simulator function only, preventing use of the clinical monitoring functions of the jPulseOx in countries where economic and legal requirements make it unpractical for a non-for-profit project to meet regulatory requirements for therapeutic devices. The jSimPulseOx will be sold to hospitals and training institutes in Western countries to help finance provision of free pulse oximeters to developing country hospitals.

The jfish project will maintain itself as a not for profit organisation. Any incoming moneys are expressly for use in achieving the projects primary goal.

Device design Goals

  • Device
    • Small, stand-alone, handheld device.
    • Primarily battery powered, but readily adpats to alternative sources.
    • Separate and detachable oximeter finger probe.
  • Function
    • Measures and indicates oxygen saturation - 0-100%
      • Accuracy 75-100% +/- 3% (digital & audible)
    • Measures and indicates heart rate - 0-300 bpm
      • Accuracy +/- 3% (digital & audible)
    • Measures and indicates tissue perfusion - (LED bar graph)
    • Factory-set simulation mode
      • Provides for instructor controlled oxygen saturation and heart rate display for student simulation.
  • Cost
    • Component cost under or as close to US$30 as possible in 200-unit quantities.
    • Construction cost (components/labour) under or as close to US$50.
  • All resultant intellectual property to be released under appropriate project jfish licenses.

Design Priortities

  1. Open and free design, schematics, construction details and usage instructions.
  2. Clinically accurate and safe.
  3. Low construction cost.
  4. Simple to use; language agnostic.
  5. Low power consumption.
  6. Accessible design; use of readily available components.
  7. Firmware readily user upgradeable.
  8. Design provision for future networking with similar devices
  9. Data capture and interrogation.

Technical Specifications

  • Form
    • Standalone, handheld device.
    • Pocketable size - reference design size 83x54x31 mm, but larger considered if required.
    • Pulse oximeter probe not physically integrated with the device, but connected by a detachable lead.

 

  • Function
    • Measures and displays oxygen saturation in range SpO2 0-100% (Accuracy 75-100% +/- 3%).
    • Accurately measures and displays heart rate (Accuracy 0-300 bpm +/- 3%).
    • Displays beat-to-beat perfusion via LED bar graph.
    • User selectable error-ranges for HR and SpO2, readings outside range result in alarm.
      • Alarm can be silenced for 120s.
      • Alarm volume adjustable from 1 to 5 (1 step incremennts).
    • Low battery alarm indicates when less than 30 minutes continuous operation possible.
    • User selectable continuous operation or spot check (10s).

  • User interface
    • Must be intuitive, and as language-agnostic as possible.
    • Graphic LCD defaults to show:
      • Saturation
      • Heart rate
      • Perfusion waveform
    • User can select other displays:
      • Navigate through basic menu system
      • Set alarm limits
      • View history
      • Set default display - font sizes; information displayed.
      • Set tone volume
      • Run basic diagnostics
    • Modulated beat-to-beat audio tone, indicating saturation.
    • Joystick interface to select options and navigate menu.
  • Requirements
    • Battery powered - capable of operating from no more than 4.5 V (3x 1.5 V cells). Ideally would be operatable from 2.5-3 V (2x 1.5V or 1.25V cells), making it easy to adapt to solar power or solar charging.
    • Primarily controlled by an Atmel AVR microcontroller. Effort should be made to perform as much processing as possible in software via the AVR, avoiding unneccessary components.
      • ADC should be a feature of the selected AVR.
      • Which AVR microcontroller? ATMega16, ATMega32, ATMega64, ATMega128. The ATMega64 appears to be the best balance between features, memory & price (~AUS$12 each).
        • Require 10 bit ADC & ability to drive graphic LCD.
    • Firmware written in C for the AVR.
    • Graphical LCD display allows easy customising of displayed information. 128×64
    • Design should require only standard, commonly available components.
    • Exposed serial IO port for later integration with other devices.
  • Battery
    • powered by 2x AA or AAA batteries
    • battery life 100 h (alkaline AA 2x 1.5V)
    • Low battery indicates 30 minutes of battery time remaining
  • Modes of operation
    1. Continuous
    2. Single check for 8 seconds
    3. Simulation
  • User interface
    1. Input
      • On/Off slide switch
      • Silence 120 sec / sound off
      • Alarm set
    2. Output
      • SpO2 - 3 digit 7 segment LED display
      • HR - 3 digit 7 segment LED display
      • Perfusion - LED bar graph
  • Functionality
    • Oxygen saturation - 0-100%
      • Accuracy 75-100% +/- 3%
    • Heart rate - 0-300 bpm
      • Accuracy +/- 3%
    • Perfusion - LED bar graph
  • Costs
    1. 2x 3 segment display - $5
    2. Atmel Microcontroller - $10
    3. Sensors - ~US$15

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