ESE 350

Cuff Pressure Digital Monitor and Controller

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Introduction

The goal of this project is to provide medical professionals with a way to digitally monitor the pressure of the cuff in an endotracheal tube. Additionally it adjusts the pressure to keep it within a specified range to maintain patient safety.

More photos and details can be found on our blog

Baseline Goals

  • Digital Cuff Pressure Monitoring to provide feedback to medical professionals

  • Sound Warnings to alert medical professionals of out-of-range pressure readings

  • Automatic Inflation / Adjustment to accurately inflate the tube to correct pressure, and stabilize the system

Stretch Goal

  • Automatic determination of ideal pressure to account for different tracheal diameters across patients and breathing cycles

Basic structure

We decided early on that the best way to adjust the pressure would be to mechanically replicate the way that doctors adjusts the pressure, i.e. a syringe pump. This would adjust the pressure through a length of tubing that was also connected to a pressure sensor. Additionally we would display the values on an LCD and allow buttons for user input of the pressure range. The key here was to accurately adjust the syringe pump according to the pressure sensor. Additionally we wanted to stay as compact as possible, though we found the limiting factor was the size of the syringe, i.e. the amount of air we could insert, i.e. the range of pressures we wanted to able to adjust within.

Actuation

We started with using a servo and a laser cut printed rack and pinion to move the syringe. Quickly we realized this would be hard to integrate, and also would not allow for precise control of the syringe. A better choice was a stepper motor. We used a threaded rod and some more custom cut pieces to hold the syringe onto the threaded rod. This allowed us to accurately step the the motor and syringe together.

Tubing

To both adjust the pressure and measure the pressure we fashioned essentially a y-splitter from some plastic tubing and medical syringes. We used the syringe to keep a universal access port to plug into endotracheal tubes exposed to the doctors and split this into a tube attached to our sensor, and a another universal port that we attached to our syringe. The connections needed to be very airtight in order to prevent air leaks, as the sensor would show a pressure drop very quickly with air leaking from it's section of the tubing, even if only minimal air leaked from the cuff. We accomplished this with super glue around all our connections.

UI

We chose to keep a simple interface with users interacting via physical buttons because of the use in medical/surgical settings. We used an LCD to display the current cuff pressure. We also had a buzzer that would inform the user any time the pressure got out the specified range and could not be corrected (i.e. it was very out of range).

Final integration

After moving from a rough duct-taped syringe pump to a well put together system and from a messy breadboard to a neat soldered proto-board we put it all in a laser cut box and had a working product!

Built With

  • cpp
  • mbed
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