Dr. Susan Eagle of Vanderbilt Medical Center's Division of Cardiothoracic Anesthesiology challenged us to develop a technique for measuring lactic acid concentration in a patient in real-time without drawing blood. As undergraduates in Vanderbilt's Biomedical Engineering program we resolved to apply concepts we had learned in class as well as the intensive work ethic developed during our time at the university in order to take on this far-reaching, critical issue.
What It Does
This prototype serves as a proof of concept for a device which uses phototransistors to detect wavelengths of light in the Infrared Spectrum and outputs usable data.
How We Built It
After spending the first 9 hours of the Hackathon conducting research and putting together a theoretical design, we directed our energy towards proving a foundational principle of our design: detection of light in IR wavelengths can be accomplished inexpensively in in real-time. We started with a sketch on a whiteboard which quickly allowed us to identify the components we needed: an arduino microcontroller, LED, IR light source, and a photoresistor. With the help of Major League Hacking we were able to obtain all the parts we needed, and, after some critical IT support from MLH coordinator Shy, get the arduiono connected to a laptop. After overcoming an initial learning curve and some functionality issues in our LED we hit the ground running and wrote a simple, but highly sensitive program for detecting low-energy light (i.e. infrared light). Once we had everything up and running it was time to put our device to the test. Our code was designed to turn on an LED when the photoresistor detected near darkness; therefore, the LED would only turn off if the photoresistor experienced a blast of light energy. Sitting in darkness we ran the code and aimed our IR source, a Samsung Galaxy S6, at the photoresistor. We activated the beam and sent several pulses of invisible light at the device, and, to our excitement and relief, the LED blinked off and on in sequence! We conducted dozens of additional trials controlling for other sources of light until we were certain that stimulation from the IR source alone was causing activity in the photoresistor. Once this was proven, all that was left was to build the housing for the device, and begin dreaming up the next iteration of LARS.
Challenges We Ran Into
One of the greatest challenges we encountered was identifying the ideal wavelengths of light absorbed by lactic acid. Although this is an incredibly common and well studied chemical in medicine, the literature of UV-vis spectroscopy of lactic acid is limited. These ideal wavelengths (i.e. the "LARS wavelengths") were actually discovered by a team in Spain conducting spectroscopic analyses on compounds found in wine; luckily for us, lactic acid is one of those compounds so we were able to obtain two unique peak absorption wavelengths in the IR spectrum. The entire project hinged upon the discovery of these wavelengths.
Other problems from faulty connections and broken diodes, to coding errors and upload issues presented significant and frustrating time delays, but were thankfully corrected with more than a little help from our gracious VandyHacks hosts.
Although there are existing products which make use of light spectroscopy to obtain lactic acid concentration, none of these devices do so directly. All current devices obtain measurements for other molecules in the body such as hemoglobin and then rely on an algorithm to ascertain and estimate lactic acid concentration. We have identified a technique which allows for direct measurement of lactic concentration without drawing blood and without presenting large cost or time barriers.
What We Learned
Research is everything. This entire project was made possible through the identification of the LARS wavelengths, an endeavor which was only accomplished after 9 hours of pouring over scientific journals and databases.
What's Next for L.A.R.S. - Lactic Acid Real-Time Spectroscopy
The next iteration of LARS will take the form of a wearable wristlet implenting a Adafruit Trinket - Mini Microcontroller along with LARS wavelength infrared strip LEDs, and indium-gallium-arsenide photodiodes in order to collect a lactic acid absorption spectrum directly from the blood vessels in the wrist.