Team Poor Circuit-lation Members

Serena Tang

Fourth year bioengineering major.

Alice Tor

Fourth year biosystems major.

Sana Khan

Fourth year bioengineering major.

Continual and mobile heart rate monitoring is an incredibly powerful source of biometric data that can reveal a myriad of subject-specific health conditions and pathophysiologies. Examples include tachycardia, which may be symptomatic of more serious cardiac events, like stroke or cardiac arrest [1]. A more serious example of a cardiac event that can be detected via heart rate monitoring is heart failure, where early detection is especially important due to the immediate effects of hypoxia [2]. Additionally, monitoring heart rate during less stressful events, such as exercise, can improve long-term heart health and prevent cardiac damage [3]. However, modern solutions tend to be either too expensive or uncomfortable and immobile, making this technology inaccessible to many and poorly suited to everyday life. Furthermore, the populations that stand to benefit most from continual heart rate monitoring are often underserved and more prone to factors that cause health disease, and lack systemic access to quality healthcare [4]. Rising national poverty rates also contribute to the increasing wealth gap, further highlighting the necessity for accessible medical devices and technologies [5].

Themes: School of Medicine

Current Solutions

Currently, there are two major categories for existing solutions: smartwatches and medical heart rate monitors. Certain smartwatches, like the Apple Watch, work by conducting EKGs which have users complete the circuit by putting their finger somewhere on the watch. Other smartwatch systems can monitor the heart rate by using pulse oximetry, which shines LEDs and IR LEDs on to the user’s wrist to determine the heart rate. While these solutions are extremely mobile, comfortable for long time use, and feature many additional features, such devices are commonly very expensive. While the price may be considered low to some, many who struggle to afford groceries, medication, and/or will not be able to afford such a device. Even if such a device was suggested by their medical care physician, insurance companies are not guaranteed to reimburse the full cost of the device.

On the other hand, medical heart rate monitors, such as a 6 lead EKG or fingertip pulse oximeter, are much less expensive, they are often extremely bulky and not mobile. Additionally, many people may struggle with learning how to use such a device, such as older folks, who are a major subgroup who will benefit from such a device. Furthermore, many times, these devices are single use, which can cause ethical, environmental concerns for many.

Proposed Solutions

As our arterial blood vessels pump oxygenated blood around the body in synchrony with out cardiac heart beats, the volumetric changes in blood flow can be seen in the chnage in absorbed light by blood vessels. We plan to harness this change in absorbed light using photoplethysmography (PPG). A PPG uses a light source and a photodectors to detect the change in light absorption to track volumetric changes in blood flow. The AC component of this biosignal reflects the pulse activity while the DC component reflects blood protein concentrations, blood oxygenation level, and other biometric information.

In our project, we plan to create a mobile, low cost, heart rate monitor that allows users to wear the monitor around their wrist for longs periods of time whie displaying their heart rate. In order to accomplish this, we can to use a reflective-mode PPG which allows us to collect the heart rate from a single plane of skin. As a PPG is small and low-cost, this will allow us to create a very low cost heart rate monitor compared to already existing solutions.

As a proposed solution will have to be a suitable replacement for smartwatches and medical heart rate monitors, solutions must be mobile and comfortable for long time wear as well as be highly accurate. Therefore, a long time wear test to test it comfortability will need to be conducted to understand if it is suitable for long time wear; if users feel uncomfortable wearing the device for long periods of time or develop a skin condition, such as a rash, the device may not be suitable for long term, mobile use. Additionally, the device must provide an accurate heart beat; such measurements may be directly compared to current commercially available devices or by manually determining our heart rate.

Project photos

Above is a photo the Arduino interface which shows a PPG signal. From this signal, we will be able to extract a heart rate and display it on an OLED screen.

Above is a preliminary version of our PPG case without any straps.

Above are photos of our working PPG cricuit on a breadboard with a heartrate being displayed when a finger is on the phototransistor.

Above is a photo of our PPG circuit inside its case. The OLED screen is also shown under the top of the case.

Schematics

Photoplethysmography (PPG) Arduino nano shield schematic.

Drawings

PCB case inspired by Hello Kitty; case does not show watch straps. While the outer cover shows Hello Kitty, the cover can be opened to show the OLED screen, which displays the heart rate. The Arduino Nano and its components are housed inside the case and the opening on the bottom allows for the phototransistor to be in contact with the wrist.

Project Video

Final Presentation Slide Deck

Poster

Resources used in problem definition

Heart Health Information

[1]Tachycardia - Symptoms and causes. (2022, January 8). Mayo Clinic. https://www.mayoclinic.org/diseases-conditions/tachycardia/symptoms-causes/syc-20355127

[2]Heart failure - Symptoms and causes. (2021, December 10). Mayo Clinic. https://www.mayoclinic.org/diseases-conditions/heart-failure/symptoms-causes/syc-20373142

[3] Mutter, E. L., & Abella, B. S. (2016). Duration of Cardiac Arrest Resuscitation: Deciding When to “Call the Code.” Circulation, 133(14), 1338–1340. https://doi.org/10.1161/circulationaha.116.021798

Accessibility Stats

[4] Heart Disease: It Can Happen at Any Age | cdc.gov. (2021, January 26). Centers for Disease Control and Prevention. https://www.cdc.gov/heartdisease/any_age.htm

[5] US Census Bureau. (2021, October 18). Income and Poverty in the United States: 2020. Census.Gov. https://www.census.gov/library/publications/2021/demo/p60-273.html

Resources used in creating our solution

Oxygen Saturation in Blood

[6] Nitzan, Meir & Taitelbaum, Haim. (2008). The measurement of oxygen saturation in arterial and venous blood. Instrumentation & Measurement Magazine, IEEE. 11. 9 - 15. 10.1109/MIM.2008.4534373

[8] Dzedzickis, Andrius & Kaklauskas, Arturas & Bučinskas, Vytautas. (2020). Human Emotion Recognition: Review of Sensors and Methods. Sensors. 20. 592. 10.3390/s20030592.

Sensing Heart Rate

[9] Allen, J. (2007). Photoplethysmography and its application in clinical physiological measurement. Physiological Measurement, 28(3), R1–R39. https://doi.org/10.1088/0967-3334/28/3/r01

[10] Apple. (2021, December 13). Monitor your heart rate with Apple Watch. Apple Support. https://support.apple.com/en-us/HT204666

[11] https://www.mouser.com/datasheet/2/427/VISH_S_A0003153719_1-2568779.pdf

[12] MedHealth.Tech. (n.d.). Photoplethysmography - How the Apple Watch measures your heart rate for the Non-Technical. MedHealth.Tech - Medical Health Technology. https://www.medhealth.tech/2017/05/photoplethysmography-how-apple-watch.html

[13] Baker, Stephanie & Xiang, Wei & Atkinson, Ian. (2017). Internet of Things for Smart Healthcare: Technologies, Challenges, and Opportunities. IEEE Access. PP. 1-1. 10.1109/ACCESS.2017.2775180.