Breathing Machine

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Breathing Machine
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Design Requirements

• Provide/Remove 500cc of air
• Rate 15 breaths per minute
• Ability to vary volume of air, and rate

Age (years) Weight (kg) Tidal Volume (cc)
Child 10 33 200 - 270
Teenager 17 55 330 - 440
Adult 73 440 - 580
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Existing Breathing Machines

• The need for artificial breathing mechanism has
  always been around with human history
• 1896 ODwyer used a foot operated pump which
  blew air into patients lungs through a curved
  metal tube

Existing Breathing Machines
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Current Respirators

• Air-Shielded Electric Ventilators
• Mörch Piston Ventilators
• Bennett Respirators

Existing Breathing Machines
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Air-Shielded Electric Ventilators

• Blows atmospheric air into the lung using an
  electric powered blower that compresses and
  expands rubber bellows inside a rigid container
• Uses one-way valve
• Only works for inhalation

Existing Breathing Machines Air-Shielded
Electric Ventilators
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Mörch Piston Ventilators

• Uses a circular plate with a rod connected to a
  piston
• Motor provides force
• Circular plate controls volume
• For either inhalation or exhalation

Existing Breathing Machines Mörch Piston
Ventilators
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Bennett Respirators

• Operates with patients initiation
• Patient breaths in, low pressure causes spring to
  pop, and the valve opens since it is connected to
  the spring diaphragm
• Compressed air comes in until the pressure
  difference between either side of the valve
  becomes small

Existing Breathing Machines Bennett Respirators
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MUSSL Breathing Machine
Inhalation
Exhalation
INNER BEAM
OUTER BEAM
No tilting of the plate
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Machined Components

• Casing
• Cam Supports
• Cams
• Beam and Slider
• Bellows Plate
• Weight Sealing ? Plexiglass

Design Justification Choice of Materials
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How it works

• Fully-Compressed
• (2 inches)
• Fully-Expanded

(12 inches)
Neutral position
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Expansion
Exhaust Air from the lung
Fresh Air
Allowed Flow Direction
Neutral position
Fresh Air trapped
Exhaust Air trapped
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Compression
Trapped Fresh Air flows into the lung
Trapped Exhaust Gas escapes to ambient
Neutral position
Fully-Expanded
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Issues

• Problems 1) Difficulty in synchronizing 2 motors
• 2) Severe sliding of outer beam
  along inner beam
• - leads to bending of the bellows

Bending of the bellows
Plate remains HORIZONTAL
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The Final Design

• 3D-Model

Bellows Guide
1 Motor
Timing Belt and Pulleys
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Breathing Rate Control

• Variation of motor speed
• Method
• Resistive speed control
• PWM speed control

Design Description Breathing Rate Control
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Resistive Speed Control

• R1 motor, R2 resistor
• Resistor reduces voltage delivered to motor
• Simple to implement
• Extreme inefficiency and possible danger

Design Description Breathing Rate Control
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PWM Speed Control

• PWM Pulse Width Modulation
• Splits voltage supply into pulses and controls
  the pulse width, hence the total voltage
• Each pulse carries full voltage torque

Design Description Breathing Rate Control
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PWM Circuit
Design Description Breathing Rate Control
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Performance

• Provide/Remove 500cc of air
• Rate 15 breaths per minute
• Ability to vary volume of air
• Ability to vary breathing rate

Machine Testing
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Integration with Lung Model