When wearable tech doesn't need to be worn
A surprisingly old technology with exciting potential in remote monitoring and disease screening
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🤷♂️ Problem
Chronic disease monitoring often requires invasive investigations carried out by healthcare professionals in locations away from the home.
The majority of global deaths each year (71% in 2016) are due to non-communicable diseases. Cardiovascular diseases are the biggest contributor.
💡 Solution
Leverage wearable technology and large datasets to allow some aspects of chronic diseases to be monitored routinely, independently and through non-invasive methods.
Define new digital biomarkers that, when combined with readily available patient insights, can assist with disease screening and early diagnosis.
📖 Terms
Photoplethysmography (PPG) - an optical technique that measures changes in light absorption and can be used to detect blood volume changes. Shine a light through your wrist or finger - anywhere with a decent vascular bed, then quantify the light that is scattered back.
📚 History
German physician Karl Matthes (1905-1962) developed the first device to measure oxygen saturation back in 1935 using red and infrared filters.
This early use-case of what would become PPG was adopted by American Physiologist Glenn Millikan to make an ear oximeter which alerted pilots in World Ward II to low blood oxygen saturations.
It wasn’t until the 1980s however that pulse oximetry started to become routinely used in clinical practice.
💼 Use cases
Established
Pulse oximetry (blood oxygen saturation and pulse rate)
Emerging
👥 Players
Commercial
BioBeat - FDA approved PPG products for realtime, continuous monitoring
Valencell - provides the underlying PPG technology for wearable manufacturers
Lifelight - contactless clinical observations supported by NHS England
Consumer
Oura - wearable ring with recent partnerships in the US sporting world
Fitbit - popular activity trackers
Garmin - activity and fitness tracking
Xiaomi - budget fitness trackers
Apple - seeking firmer clinical credentials for A Fib detection and oxygen saturation measurements
🔮Predictions
Current experimental/research applications for PPG will mature.
PPG based technologies will move from disease monitoring to disease diagnosis. New biomarkers found using PPG technologies will improve diagnostic certainty or at least reduce the need for some invasive tests.
PPG signals will become more resilient to motion artefacts, which currently limits their accuracy during movement or exercise.
PPG technologies will facilitate better ‘self-care’ - helping people monitor and manage their own conditions.
The promise of PPG-based biomarkers will only be realised with quality physiological datasets that will help derive meaning from the signals
Backlash against both consumer and medical manufacturers will arise unless adequate validation is done on wearables worn by those with darker skin.
🌅 Opportunities
Remote PPG (rPPG) aims to take devices off people’s wrists and fingers and remotely record and interpret PPG signals through advanced camera technology.
Speckleplethysmography (SPG) provides benefits over PPG such as increased signal amplitude and less susceptibility to temperature-induced vasocontriction.
Further research into biomarkers like heart rate variability (HRV), that can be measured using PPG but currently remain in the realm of lifestyle/sport fitness applications rather than clinical pathways.
🔗 Links
A digital biomarker of diabetes from smartphone-based vascular signals - Nature paper investigating PPG from a smartphone app as an easily attainable biomarker
The use of photoplethysmography for assessing hypertension - another Nature paper exploring the relationship between PPG signals and blood pressure
Real-time quantifying heart beat rate from facial video recording on a smart phone - paper describing an rPPG technique to acquire heart rate from a smartphone video recording
Thanks for reading, see you next week 👋
Sandy