Automated Blood Pressure Cuff

The objective of this instructable is to create an automated blood pressure cuff using an Arduino Uno and simple electronic parts. This device will allow one to measure their mean arterial pressure (MAP) in about one minute. Previous Arduino coding and circuit design experience is not necessarily required, as this tutorial will provide a detailed step-by-step walkthrough.

Gathering the Materials

For this project you will need the following:

- Arduino Uno (1)

- Arduino USB Cable (1)

- Arduino Software Downloaded onto Computer (1)

- Pressure Transducer (Honeywell ASDX 015PDAA5) (1)

- A 3-5V DC Motor (3V DC KOGE Mini Pump KPM14A) (1)

- Dump Valve (3V DC Air Release Valve KOGE) (1)

- 2N3094 transistor (1)

- Two 100 Ohm Resistors (or one 200 Ohm Resistor)

- Wire

- Generic Manual Blood pressure cuff (1)

- 3-way Valve (1)

- 4-way Valve (1)

- Extra Tubing

- Bread Board (1)

- Multimeter (to troubleshoot) (1)

Extra:

- Soldering Iron (1)

- Solder

- Simple PC Board (1)

Constructing the Circuit

See attached image for detailed circuit diagram. Note: attaching to these specific Arduino pins will allow you to implement our code (provided in last step).

Arduino Code

The Arduino code was written to integrate the pressure transducer and microcontroller to allow functionality of the device. The first step is to ensure that the dump valve remains closed while the pump inflates the BP cuff. Next, the BP is inflated to a pressure of 200mmHg to begin the test. Before the software commands for deflation of the BP cuff, the exact initial pressure is recorded (~200mmHg). The BP cuff is then deflated in intervals of approximately 5mmHg - 10mmHg, and the pressure is recorded at each interval. Once the program deflates the BP cuff to about 60mmHg, enough data points have been recorded for the software to determine the mean arterial pressure. The calculated MAP is displayed in the serial monitor upon completion of the program. Additionally, the BP cuff is deflated all the way automatically at the end of the test.

Implementing Breadboard Practice Run

Please note that the provided picture is not a complete circuit. Always make sure you check your circuit before moving onto a PC Board. The transistor functions as a switch to allow the appropriate amount of current to flow into the motor during inflation of the BP cuff.

Soldering to PC Board

Seeing the Results!

When performing the final run it is important to put the cuff high around your bicep, and to have no motion during the stepwise drop of pressure (this is when values are being saved). The less movement during the test, the more accurate the calculation will be.

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