Measuring a change in distance using proximity sensors

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Dear Sparkfun community,

I am currently undertaking a project where I am trying to derive the respiratory rate of a subject. One of the ways to do this is by monitoring the expansion and contraction of the chest during breathing. I’m thinking of approaching this by using a sensor to monitor the changes in distance of the chest wall. What I’m unsure about is the sensor to use.

I’ve come across a number of proximity sensors on Sparkfun and elsewhere but am unsure of their capability. Could anyone advise me on which might be best to use out sensors listed below:

  • Infrared Proximity Sensor

    Ultrasonic Range Finder

    Laser-Based Optical Ranging Sensor

    • What concerns me is their sensitivity. During respiration the chest wall expands by roughly 2cm-4cm. Would the listed sensors be capable of picking up changes of this size?

    Thanks in advance!