Opto-physiological monitoring (OPM) research has been ongoing for over two decades. It has been well developed as a new scientific theory that goes beyond existing Lambert-Beer law driven photoplethysmography (PPG). OPM comprehensively models light interacting with all tissue components, including blood, skin, muscle, bone, ligaments, etc.

PPG-based devices have dominated human vital signs monitoring and assessment, such as heart rate and blood oxygen levels, for over 40 years, yet concerns about their reliability remain. This was most recently reinforced during the COVID-19 pandemic when pulse oximetry devices received unprecedented attention for their essential role in COVID-19 patient management. Clinicians, researchers, and patients were alarmed by the many reports and studies reconfirming the technology’s inaccuracy in patients with darkly pigmented skin. As a result, the FDA issued an advisory note warning of the limitations and “risks of inaccuracy” of pulse oximeters. Significant work is ongoing by pulse oximeter manufacturers to overcome pulse oximeter’s unreliability.

The global pulse oximetry market was valued at UD$ 2.87 bn in 2023. This market is just a fraction of the total market for clinical grade wearable sensors, which is expected to hit around US$170 bn by 2030.

OPM research platform overcomes the limitations associated with PPG technology (including smart watches, etc.) by addressing three major challenges that undermine present pulse oximetry and related technologies, including:

1. Skin tone with dark pigmentation
2. Low blood perfusion
3. Motion artifacts

OPM system combines optical and electrical measurements with real-time dynamic adapted filtration algorithms to provide a robust solution that is insensitive to physical motion. The platform compares favourably with commercial devices. The multi-wavelength illumination offers additional functionality, such as the ability to measure peripheral capillary oxygen saturation (SpO2), heart rate (HR) and respiration rate (RR) etc.

Besides its obvious application in the field of personal healthcare, where OPM provide a cost-effective solution to obtain comprehensive vital signs recordings, OPM also has direct applications in sport physiological monitoring and assessment during physical activity.

The platform uses the OPM technology platform provided by Carelight Ltd, and the facilities available in the Wolfson School of Mechanical, Electrical and Manufacturing Engineering, including the Photonics Engineering and Health Technology Lab with access to static bikes and treadmill machines, a workstation for AI-driven signal processing, Mobile APP with smartphone, and smartwatch devices.

This platform has delivered preliminary yet promised outcomes compared with the commercial standard PPG sensors. More importantly, a robust and cost-effective physiological monitoring system has been established to reliably measure physiological parameters and vital signs regardless of the user’s physical movements. 

OPM has created a new avenue to generate a more complete and robust engineering solution for monitoring vital signs and other biomarkers, enabling high definition signal capture in real time and anytime.

Dr Laura Barrett, Exercise Physiological Monitoring and Assessment in School of Sport, Exercise and Health Sciences, Loughborough University, UK.

Dr Mahsa Derakhshani, Real time and Machine Learning Opto-physiological signal Processing, School of Mechanical, Electrical and Manufacturing Engineering, Loughborough University, UK.

Prof Steve Greenwald, Real time Cardiovascular Assessment, Blizard Institute, Queen Mary, University of London, UK

Collaboration for OPM Research and development is highly welcome via the Photonics Engineering Research Group (Sijung Hu) or Carelight Limited (Martin French).