Hacking an Automatic Blood Pressure Cuff: DIY Ventilator

Emergency ventilator CAD model, using an automatic blood pressure monitor/cuff to squeeze an Ambu-bag.

Update Log

This project is actively in development, and this post will be updated regularly.

The Team & Challenge

From left to right: Millen Anand (ma3617@columbia.edu), Ginny Jeong (hj2502@columbia.edu), Nathalie Limandibratha (nbl2116@columbia.edu), Connor Evans (cde2119@columbia.edu).

Design Objectives

  1. Zero Manufacturing: Simpler; increases modularity; cheapest and fastest; no need for technician or engineer; globally adaptable
  2. Utilize Existing Hospital Equipment: Medical-grade, reliable; Hospitals have many automatic Blood Pressure (BP) monitors (source: Johns Hopkins, Mount Sinai)
  3. Meet Need for Large Quantity: Ventilator need increasing exponentially in the US, Commercial ventilator production too slow

Building Off a Proved Design

Manual Blood Pressure Cuff Ventilator (Dan Bruder)

Our Design: Automatic Blood Pressure Monitor Ventilator

Automatic Blood Pressure Cuff Ventilator, shown without wiring and electronic components.

Advantages of Automatic BP Monitor

  1. Prevalent in hospitals: utilizing medical-grade equipment; Hospitals have many automatic BP cuffs (Johns Hopkins, Mount Sinai)
  2. Repurposable: Cheaper/easier than fabricating actuation mechanism; Perfect compressive function; monitors already have pump, solenoid valve, tubing
  3. Adjustable / Flexible: Any automatic BP device brand or model works; Easily accommodate different BVM sizes; Easy override if automatic ventilation fails — unstrap for manual ventilations
  4. In-line pressure measurement: Enables accurate pressure measurement by use of cuff pressure; Sanitary as air volume of BVM and BP cuff don’t interact

Device Functionality & Airflow

Components native to most blood pressure monitors include pumps, solenoid valves, and tubing.

Electronics Subassembly

Simple hobby electronics enable powerful control and adjustment capabilities for HCPs.

Basic Specifications

  1. Min/Max Pump Rate: 0–34 pumps/min, adjustable with potentiometer
  2. Amplitude Range: 0–6 in (verify with testing), adjustable with potentiometer
  3. Sensed Conditions: Ambu-bag pressure, cuff pressure
  4. Safety Measures: Ambu-bag pressure drop alarm, cuff disconnect alarm

Full Parts List & Construction Info

At only $118.44 additional cost per ventilator to hospitals, the design enables large-scale ventilator production.

Caveats & Disclaimers

There are several issues yet to be tested and ironed out. These will be updated as assumptions are tested.

  1. Pump inflation effectiveness: Achievable breath rate with built-in pump will need to be verified to ensure full breath rate range is possible.
  2. Adjusting for different BP monitors: Current design is based on Omron BP monitor. Different monitors have varying air pump components, which may affect voltage settings. Most automatic BP monitors operate very similarly, but will require testing and calibration of different monitors to verify.
  3. Determining voltage settings: Voltage is critical to determine compression rates and amplitude. Will be determined through experimentation.
  4. Drop in pressure in Ambu bag: Most accurate pressure sensor is in the BP monitor and not in the Ambu bag. A pressure sensor (force sensitive resistor) between the Ambu bag and plywood base will be tested to determine effectiveness.

References & Acknowledgements

Design Proof of Concept: Dan Bruder



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