Breathing Machine

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 Teenager Adult

Existing Breathing Machines The need for artificial breathing mechanism has always been around with human history 1896: O’Dwyer used a foot operated pump which blew air into patient’s lungs through a curved metal tube Existing Breathing Machines

Current Respirators Air-Shielded Electric Ventilators Mörch Piston Ventilators Bennett Respirators Existing Breathing Machines

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

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

Bennett Respirators Operates with patient’s 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

Inhalation Exhalation No tilting of the plate OUTER BEAM INNER BEAM MUSSL Breathing Machine

Machined Components Casing Cam Supports Cams Beam and Slider Bellows Plate Weight & Sealing  Plexiglass Design Justification: Choice of Materials

How it works … Fully-Compressed (2 inches) Fully-Expanded (12 inches) Neutral position

Expansion Fresh Air Neutral position Fresh Air trapped Exhaust Air from the lung Exhaust Air trapped Allowed Flow Direction

Compression Neutral position Trapped Exhaust Gas escapes to ambient Trapped Fresh Air flows into the lung Fully-Expanded

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

The Final Design 3D-Model Bellows Guide 1 Motor Timing Belt and Pulleys

Breathing Rate Control Variation of motor speed Method 1.Resistive speed control 2.PWM speed control Design Description: Breathing Rate Control

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

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

PWM Circuit Design Description: Breathing Rate Control

Performance  Provide/Remove 500cc of air  Rate ≈ 15 breaths per minute  Ability to vary volume of air  Ability to vary breathing rate Machine Testing

Integration with Lung Model