PhO 2 Smartphone based Blood Oxygen Level Measurement using Near-IR and RED Wave-guided Light Nam Bui, Anh Nguyen, Phuc Nguyen, Hoang Truong, Ashwin Ashok, Thang Dinh, Robin Deterding, Tam Vu 1/30
Chronic Obstructive Pulmonary Disease (COPD) Leading cause of death in the US, 2016 24 Million Americans have COPD Early detection of COPD is key to successful treatment OFTEN FOUND IN LATE STAGE $34,000 treatment in ICU 2/30
Vital signs screening in COPD Blood pressure Heart rate Oxygen Saturation needs to be measured frequently Oxygen saturation (SpO2) Breathing rate Wheezing sound 3/30
Oxygen Saturation (SpO 2 ) Oxygenated hemoglobin Deoxygenated hemoglobin O 2 O 2 O 2 O 2 Sp02 = No. oxygenated hemoglobin Total No. hemoglobin 100% 4/30
Non-invasive Measurement of Oxygen Saturation IR emitter Red emitter Intensity Intensity t AC IR AC R AC t Sp02 = f AC R AC IR Photon Detector R IR 5/30
Red and IR Wavelength Selection Harmful Low penetration Absorbed by red pigmentation At Red= 660 nm and IR = 960 nm, the difference of light absorption by oxygenated hemoglobin and deoxygenated hemoglobin is largest. 6/30
Dedicated Hardware Solutions Smartphone-based blood oxygen measurement Pros Cons High accuracy Inconvenient Costly
A solution to capture the oxygen level and is High accuracy. Low-cost. Easy to make by patients 8/30
PhO 2 Smartphone based Blood Oxygen Level Measurement 9/30
Hardware Challenges PULSE OXIMETER PHONE BASED PULSE OXIMETER IR emitter Red emitter Light Source 10/30
Challenge. Phone s camera IR filter IR filter Sensor 11/30
Existing Software-based Solutions DISADVANTAGES Inaccurate: Green channel is mostly absorbed by red pigmentation. Coarse-grained: one record per 10 seconds. RGB Color Image Red Light IR Light DigiDoc ihealthcare
Solution. Red and NIR for Oxygen Saturation Measurement NIR NIR NIR has similar characteristics of hemoglobin absorption with the IR lights. is available in most of phone s flashlight and is not filtered by the phone s camera. 14/30
PhO 2 NIR Extraction Technique Absorbed by red pigmentation Absorbe d Green filter Red and Green filter cuttoff NIR 15/30
And 5 More Challenges RGB Intensity Smartphone s camera picks up most of the lights Conversion between RGB and light intensity Pressure Micro movements Finger movement and Contact pressure Flashlight heat can cause skin burn 16/30
3D printed Optical Hardware Add-on 17/30
3D printed Optical Hardware Add-on RGB Intensity Smartphone s camera picks up most of the lights Conversion between RGB and light intensity Pressure Micro movements Finger movement and contact pressure Flashlight can cause skin burn 18/30
Wavelength selection α = arctan(a/b) ε Hb r ε Hb r R Sp02 = ε Hb ir ε HbO2 r + ε HbO2 ir ε Hb ir R b α a X:678 Y: 724 Z:1.002 λ R = 678 nm λ NIR = 724 nm 20/30
Normalized Intensity Normalized Intensity Normalized Intensity Pressure Detection and Recommendation PPG signal in a 7 seconds window Sample PPG signal in a 7 seconds window Sample PPG signal in a 7 seconds window Sample 21/30
Heat Reduction with Distributed Lighting Source H E p = hf Modify 2.55 mm 0.6 mm Bandpass filte E = To maintain the high light intensity 22/30
PhO 2 Algorithms Detecting pressure Collecting raw data 95 % PPG Calculate peak-topeak ratio Identify the peaks and troughs ROI detection and create the PPG signals 23/30
App overview PPG display Image frame 24/30
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In-lab experiments 3 males, 3 females 5 times performs the hyperventilation (a breath holding technique to reduce oxygen). Totally 560 samples. 26/30
SpO2 (%) SpO2 (%) SpO2 (%) DigiDoc PhO2 vs. Existing apps ihealthcare Measurement Indices PhO2 Measurement Indices Time (s) 27/30
Experimental results 3.5% 28/30
In hospital experiment with patient. In clinic experiment 29/30
Fine-grained evaluation of the patient Low Oxygen Level Coughing 30/30
Heat Reduction Evaluation Hand multimeter Thermalcouple Probe 31/30
Temperature (Celsius) Output temperature of different add-on designs 58.9 60 50 38.5 40.3 45 36.8 37.6 40 30 20 10 0 Without Banpass Filter With Bandpass Filter Large Tunnel Small Tunnel Multiple Small Tunnels 32/30
Conclusion Accurately measuring oxygen level using low-cost optical film filters. Detect the appropriate contact pressure between finger and phone camera. 3D-printed add-on to handle the problem of light scattering and finger movement. 34/30
Application for optical light based sensing Urea Lactate Cholesterol Optical light based sensing Water Alcohol Glucose 35/30
PhO 2 Smartphone based Blood Oxygen Level Measurement using Near-IR and RED Wave-guided Light Nam Bui, Anh Nguyen, Phuc Nguyen, Hoang Truong, Ashwin Ashok, Thang Dinh, Robin Deterding, Tam Vu 37/30