Comparison of bi-wavelength and tri-wavelength photoplethysmography sensors placed on the forehead

Photoplethysmography is a well-established minimally invasive method for estimating heart rate and blood oxygen saturation in clinical settings. Photoplethysmography, with limitations, can also be extended to estimate respiration rate. Recently many off the shelf photoplethysmography sensors have been released in a form factor suitable for wearable devices. In this study we evaluate two photoplethysmography front ends (inclusive of suitable signal conditioning module and digitizer) from Maxim Integratedâ„¢. The tri-wavelength MAX30101 sensor and bi-wavelength MAX30102 sensor were evaluated on the forehead, in a truly non-obtrusive wearable friendly position. Heart rate, respiration rate and blood oxygen saturation were extracted from both sensors and compared with a FDA/TGA/CE approved photoplethysmography device placed on the finger. All data were captured simultaneously and at rest. The MAX30101 sensor was more accurate in measuring heart rate, blood oxygen saturation and respiration rate compared to the MAX30102. Additionally, we found that the red wavelength was best for measuring heart rate and the green wavelength was best for respiration rate.