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Archive for October 6th, 2009

Innovation Lessons From the History of Pulse Oximetry (or, How One Person’s Noise is Another’s Symphony)

Posted by Plish on October 6, 2009


pulseox michaelplishka2009If anyone has ever been in an emergency room, hospital or had a medical procedure done, you no doubt have had a pulse oximeter placed on your finger (or perhaps earlobe).  The device functions by shining certain wavelengths of  light at your skin and reading the amount of light that comes back or through the tissue.

It’s a really cool device and quite simple in its operation – you could build one yourself if you wanted to.  Yet, what is today a standard in medical monitoring, was once an annoying artifact.

In the early 1970’s, Japanese BioEngineer Takuo Aoyagi was studying ways of measuring cardiac output.  At the time, the established method involved injecting dye into the blood, diverting this dyed blood from an artery through an external tube and then shining light through the tube and measuring the light that’s transmitted. 

Although it was effective it was also pretty invasive.  So, building upon this technique, researchers tried using the same technology on a person’s earlobe – shine a light through the earlobe and measure the transmitted light.  While this was a step in the right direction, the readings were spoiled by the pulsatile nature of the signal.

Enter Aoyagi-San who developed a technique to filter out the pulsatile effect.  Great, right?


Even after this adjustment it was difficult to obtain consistent values – something was creating noise in the system.  Mr. Aoyagi correctly postulated the fluctuation was due to changing amounts of oxygen bound to hemoglobin in the blood.   Rather than simply filter out the noise to obtain clean signals he focused his efforts on capturing the ‘noise’ of the fluctuations in a repeatable manner.  

The non-invasive pulse oximeter was born.

What’s the takeaway?

When designing new products we have a tendency to focus on achieving certain goals while working around, ignoring or minimizing the noise.  Instead, we should make friends with the noise and find out what it has to say to us.  We then have to have enough fortitude to pursue the elusive at the expense of what was originally the goal! 

Everyone hears the noise; only the innovative hear the symphony…

Click here to read the full story of pulse oximetry.

Posted in Case Studies, Design, Disruptive Innovation, Great Creative Minds, innovation, invention, patents, problem solving | Tagged: , , , , | 2 Comments »

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