Optical Fibre-Based Pulse Oximetry Sensor with Contact Force Detection.

Area of Science:

• Biomedical Engineering
• Optical Sensing
• Wearable Technology

Background:

• Contact pressure significantly impacts blood oxygen saturation (SpO₂) measurements.
• Existing pulse oximetry methods can be affected by pressure artifacts, reducing accuracy.

Purpose of the Study:

• To develop and validate a novel optical sensor probe integrating SpO₂ monitoring with contact pressure sensing.
• To improve the reliability and accuracy of SpO₂ measurements in applications sensitive to pressure variations.

Main Methods:

• The sensor combines plastic optical fibers (POF) for pulse oximetry with a fiber Bragg grating (FBG) for contact pressure measurement.
• A biocompatible epoxy patch houses the optical fibers, reducing motion artifacts and transducing pressure into strain for the FBG.
• FBG sensors, alongside a reference FBG, were used to ensure temperature-independent and reliable pressure readings.

Main Results:

• The combined sensor demonstrated low hysteresis and temperature immunity.
• Measurements on ten volunteers showed that contact forces between 5 to 15 kPa resulted in SpO₂ errors of less than 2%.
• Perfusion and skewness indices were used to assess photoplethysmogram (PPG) quality.

Conclusions:

• The novel combined optical sensor probe significantly improves the reliability of reflectance oximetry.
• This technology holds potential for enhancing wearable devices and optimizing garment integration for accurate SpO₂ monitoring.