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Baby Pulse Monitor

Final Presentation

A Novel Cost-effective Continuous Neonatal Heart Rate Monitor

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Team Introductions

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Importance of Heart Rate Monitoring for Neonates

Neonatal heart rate is significant indication of a newborn’s clinical health.

<100 BPM

100-160BPM

>160 BPM

Hypothermia,

Apnea

Healthy

Infection

Potential Indicators

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Neonatal Temperature Monitor (NTM)

Low-cost continuous temperature monitor for use in low resource settings

developed by Rice 360˚

Neonatal temperature monitoring:

address neonatal hypothermia to

reduce mortality

Device Components:

Reusable Temperature Probe
Reusable belt
Monitor with core temperature display and indicators

Image Source: https://bmjpaedsopen.bmj.com/content/4/1/e000655

Ethan

During our background research phase, we found it valuable to understand other existing technologies that aim to continuously monitor vital signs in low-resource settings. The Neonatal Temperature monitor, developed by Rice 360 is a low-cost reusable device that continuously measures the temperature of newborns to address neonatal hypothermia and lack of access to continuous monitoring in low-resource settings . The device consists of a reusable temperature probe in stainless steel housing with a terminally conductive epoxy thermistor, an adjustable and reusable belt with snaps to hold the probe in contact with skin above liver, and a monitor (based on an Arduino Uno microcontroller) that displayed the baby’s core temperature with indicator lights to alert hypothermia. The materials cost to fabricate an in-house prototype is $80.

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Current Methods of Heart Rate Monitoring

Image Source: https://www.mdpi.com/2227-9032/8/1/43/htm

High-Resource Settings	Low-Resource Settings
Electrocardiograms (ECG/EKG): gold standard for continuous HR monitoring Expensive Reliant on stable electrical supply Interpretation requires highly trained workers	Palpation: assesses pulse at the umbilical, femoral, or brachial arteries Inaccurate Discontinuous Auscultation: stethoscope to listen to heart beats from the chest of an infant Inaccurate Discontinuous Lack of access to stethoscopes

Shivani

In order to fully understand the status quo, we provide a comparison of current methods of heart rate monitoring in high resource versus low resource settings above. In high resource settings, electrocardiograms are used as the gold standard for continuous heart rate monitoring. However, the high cost, reliance on a stable electrical supply, and requirement for skilled interpreters prevents this technology from being widely used and accessible to low resource settings.

Given that there are barriers preventing technologies from high-resource areas from being implemented in low-resource settings, common methods of HR monitoring in low-resource settings include palpation and auscultation. While palpation assesses pulse at the umbilical, femoral, or brachial arteries, auscultation involves the usage of a stethoscope to listen to heart beats from the chest of an infant.

The problem with the status quo is that palpation and auscultation have shown to be inaccurate methods of assessing heart rate and result in a greater number of incorrect assessments of HR for neonates. These methods require immense concentration from the healthcare provider, and can present inaccuracies in situations of excessive noise or distractions. Inaccuracies in HR measurement can result in early or delayed interventions which can result increase neonatal mortality. Additionally, the manual nature of these methods prevents continuous measurement, and lack of access to stethoscopes serves as a barrier for auscultation. Thus, current methods of HR monitoring in low-resource settings place an extremely high burden on understaffed teams and do not yield accurate nor continuous results. This presents a need for a continuous heart rate monitoring technology suitable for the needs of low resource areas.

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Mission Statement

There is a need to integrate a heart rate sensor into the current design of the Neonatal Temperature Monitor (NTM) belt. This requires a low-cost, reusable, and easy-to-interpret device that allows for accurate and continuous temperature and heart rate monitoring.

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Requirements for Solution

Integrated into NTM

Low-cost

Accurate

Continuous

Easy-to-read

Rechargeable

Reusable

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Design Criteria

Criteria	Weighting	Method of Measurement	Target
Accuracy	30%	Accuracy range of HR measurement compared to gold standard	+/- 3 BPM
Cost	25%	Cost of raw materials	< $20
Ease of Use	20%	System Usability Scale	> 68 Average
Physical Compatibility with NTM	15%	5-Point User-Defined Scale	> 3 Average
Sensor Durability	10%	Accuracy after exposure to humidity and disinfectants (in controlled tests)	No changes in accuracy after controlled tests

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Reflective Photoplesmography (PPG)

Photodiode

LED

Emily

Based on the outlined design criteria and advice from our technical mentor, we decided to use reflective photoplesmography or ppg technology to measure heart rate. Reflective PPG measures heart rate by measuring the amount of light reflected back from a tissue, specifically in this case, an artery. When the artery contracts or during systole, more light is absorbed and less light is reflected. When the artery is relaxed or diastolic, less light is absorbed and more light is reflected. These alternating amounts of reflection generate waveforms that can be used to measure the beats per minute. Reflective PPG was selected due to its low-cost potential. The only materials required to perform reflective PPG is an LED and photodiode. Additionally, reflective ppg is used in several current wearable technologies like the apple watches and fitbits.

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Our Solution

Reflective PPG sensor featuring Red LED, BPW34 Photodiode, and an Arduino.
Separated by a barrier, optimizes the limited space on the NTM.
Material Cost: $4.81 (including circuit board, without Arduino), $0.55 (sensor alone)

John

For our solution we made a reflective PPG sensor, using a Red LED, an BPW34 photodiode, and an Arduino. A reflective ppg sensor requires the LED and photodiode to be separated by a barrier to ensure the light travels through the tissue before being measured. To reduce the space being used by the sensor, we are able to make the existing temperature sensor on the NTM belt act as this barrier. As the current NTM temperature sensor is currently located over the liver, we also placed our sensor over the liver. The liver features large amounts of arteries, making an ideal location for a PPG sensor.

The total cost of the prototype is $4.81. However, this includes materials that may not be included in the final design, such as the breadboard. The sensor alone only costs $0.55, well below our $20 requirement from our design criteria.

We 3D printed the housing for the sensor which which provides a rigid body that blocks out the ambient light and provide durability that allows our device to be used in different environments.

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Results - Accuracy Testing

Limitations:

Results are inconsistent and may be affected by noise and movement.

Conclusion: Accuracy does meet design criteria most of the time, however, is not consistent.

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Results - Durability Testing

Limitations:

Lack of belt for consistent pressure.
The discrepancy in results between tests could be due to movement.
Inconsistency with Lifebox.

Conclusion: Humidity does not affect accuracy, but accuracy fails to meet design criteria.

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Prototype Limitations

Accuracy:

Inconsistent results.
Vulnerable to movement and noise.

Housing:

Photodiode and LED don't fit securely into housing.
Method of attachment reported as uncomfortable.

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Future Improvement/Direction

Improvements on accuracy

Reducing movement
Filtering out consistent noise

Integration into NTM

Transition from breadboard to customized breadboard for NTM
Physical compatibility testing

Ease of use testing

Sara

Our first priority for improvement is to improve accuracy. One way we would approach this is on the hardware side, such as modifying the physical monitor to fit better on the skin. Another is looking at the software side, seeing if we can find a better algorithm to filter out more noise. Another priority is to perform ease of use testing. Due to time constraints, we did not get to testing for this, but feedback from it will allow us to make modifications that make putting on and measuring with the device more user friendly. Once these are addressed, our end goal is to integrate the heart rate monitor into the NTM. This will require physical integration into the belt as well as integration of electronics, so we can move away from our sprawling breadboard-Arduino setup into a compact design. This will require meeting with our clinical mentors to determine how best to make a user-friendly design.

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Conclusion

Our goal was to develop an accurate and cost-effective method for continuously monitoring heart rate in neonates.
We designed a cheap heart rate monitor with an +/- 2 BPM accuracy using PPG technology that will eventually be integrated into the NTM belt.
Our current device is mostly accurate, and is not affected by humidity, but can be inconsistent.
Future goals are to improve accuracy, perform additional testing, and eventually combine our device with the NTM.

Our heart rate monitor, when added to the NTM, will provide an additional tool for nurses in low resource settings to ensure survival of neonates.

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References

John Hopkins. (n.d.). EKG. The Johns Hopkins Patient Guide to Diabetes . Retrieved February 6, 2021, from https://hopkinsdiabetesinfo.org/glossary/ekg/

Johnson, P. A., & Schmölzer, G. M. (2020). Heart Rate Assessment during Neonatal Resuscitation. Healthcare (Basel, Switzerland), 8(1), 43. https://doi.org/10.3390/healthcare8010043

Kananura, R.M., Kiwanuka, S.N., Ekirapa-Kiracho, E. et al. (2017). Persisting demand and supply gap for maternal and newborn care in eastern Uganda: a mixed-method cross-sectional study. Reprod Health 14, 136 . https://doi.org/10.1186/s12978-017-0402-6

Liu, S.-H., Cheng, D.-C., & Lin, C.-M. (2013). Arrhythmia Identification with Two-Lead Electrocardiograms Using Artificial Neural Networks and Support Vector Machines for a Portable ECG Monitor System. Sensors (Basel, Switzerland), 13 (1), 813–828. https://doi.org/10.3390/s130100813

Marzorati, D., Bovio, D., Salito, C., Mainardi, L., & Cerveri, P. (2020). Chest Wearable Apparatus for Cuffless Continuous Blood Pressure Measurements Based on PPG and PCG Signals. IEEE Access , 8 , 55424–55437. https://doi.org/10.1109/ACCESS.2020.2981300

Tamura, T., Maeda, Y., Sekine, M., & Yoshida, M. (2014). Wearable Photoplethysmographic Sensors—Past and Present. Electronics , 3 (2), 282–302. https://doi.org/10.3390/electronics3020282

Patterson JK, Girnary S, North K, et al. Innovations in Cardiorespiratory Monitoring to Improve Resuscitation With Helping Babies Breathe. Pediatrics . 2020;146(Suppl 2):S155-S164. doi:10.1542/peds.2020-016915H

Laerdal Global Health. NeoBeat Newborn Heart Rate Meter . https://laerdalglobalhealth.com/products/neobeat-newborn-heart-rate-meter/. Accessed February 6, 2021.

Sosa Saenz SE, Hardy MK, Heenan M, et al. Evaluation of a continuous neonatal temperature monitor for low-resource settings: a device feasibility pilot study. BMJ Paediatrics Open 2020;4:e000655. doi:10.1136/bmjpo-2020-000655

Kumar N, Akangire G, Sullivan B, Fairchild K, Sampath V. Continuous vital sign analysis for predicting and preventing neonatal diseases in the twenty-first century: big data to the forefront. Pediatr Res . 2020;87(2):210-220. doi:10.1038/s41390-019-0527-0

Moorman JR, Carlo WA, Kattwinkel J, et al. Mortality reduction by heart rate characteristic monitoring in very low birth weight neonates: a randomized trial. J Pediatr . 2011;159(6):900-6.e1. doi:10.1016/j.jpeds.2011.06.044

Johnson PA, Schmölzer GM. Heart Rate Assessment during Neonatal Resuscitation. Healthcare (Basel). 2020;8(1):43. Published 2020 Feb 23. doi:10.3390/healthcare8010043