How does the PPG work ?

Summary

The video script discusses the PPG (photoplethysmography) technology used in a Kickstarter campaign's wearable device. PPG measures vital signs by shining light into the skin and detecting the reflected light, which varies with blood volume changes in arteries. The oscillating PPG signal, reflecting the heart's pumping activity, is translated by an app into health data like heart rate, HRV, and blood pressure, offering a non-invasive way to monitor health.

Takeaways

• 🌐 PPG stands for photoplethysmography, a non-invasive electronic technology used to assess vital signs by shining light into the skin.
• 💡 The technology uses an LED to emit light, which interacts with the skin, particularly the arteries carrying blood.
• 🔍 The arteries' diameter changes dynamically with each heartbeat, causing the light to be reflected back differently.
• 📶 A photodetector captures the reflected light and converts it into an electrical signal, known as the PPG signal.
• 📈 The PPG signal is an AC oscillating frequency that corresponds to the heart's diastolic and systolic phases.
• 🚀 The frequency of the PPG signal (f_PPG) is directly related to the heart rate, expressed in beats per minute (BPM).
• 📱 The PPG signal is processed by an application on a smartphone, which translates it into heart rate, heart rate variability (HRV), and other vital signs.
• 🔄 The technology aims to address reliability issues of PPG signals by using a constellation of sensors around the brain.
• 🛠️ The device, such as a ring, measures the oscillating diameter of the artery, which is affected by the heart's pumping activity.
• 📊 The application on the phone can extract various vital signs, including blood pressure, from the PPG signal.

Q & A

What does PPG stand for and what is its primary function?

PPG stands for photoplethysmography, which is a non-invasive optical-based technology used to assess various vital signs by shining light into the skin.

How does the PPG technology work with the LED and photodetector?

The PPG technology uses an LED to shine light into the skin, which interacts with the blood in the arteries. The photodetector then captures the reflected light and converts it into an electrical signal known as the PPG signal.

What is the significance of the oscillating diameter of the artery in PPG?

The oscillating diameter of the artery is crucial in PPG technology as it represents the dynamic changes in the artery's size due to the heart's pumping action, which is essential for measuring vital signs.

How does the PPG signal relate to the cardiac cycle?

The PPG signal is an AC oscillating frequency that corresponds to the cardiac cycle, with its maximum value relating to the diastolic phase (minimum artery thickness) and its minimum value to the systolic phase (maximum pressure wave from the heart).

What is the role of the photodetector in the PPG technology?

The photodetector in PPG technology captures the light that has interacted with the skin and blood, reflecting back the photons, and converts them into an electrical PPG signal.

How is the PPG signal processed and what information can be extracted from it?

The PPG signal is processed by an application on a smartphone, which translates the signal into heart rate data, heart rate variability (HRV), and other vital signs such as oxygen saturation and breathing rate.

What is the relationship between the PPG frequency and heart rate?

The PPG frequency, denoted as fPPG, is directly related to the heart rate. For example, a frequency of 1 Hz corresponds to 60 BPM (beats per minute), which is the physiological cardiac frequency.

How does the Kickstarter campaign relate to the PPG technology discussed in the script?

The Kickstarter campaign is likely promoting a device or technology that utilizes PPG technology. The script addresses questions and concerns about the reliability and functionality of this PPG-based technology.

What is the purpose of the constellation of sensors mentioned in the script?

The constellation of sensors is designed to enhance the reliability and accuracy of the PPG technology by providing a comprehensive set of data from different points around the brain or body.

How does the technology embedded in the 'air string' address the issues related to PPG signal reliability?

The technology in the 'air string' likely incorporates multiple sensors and advanced algorithms to improve the reliability of the PPG signal by mitigating issues such as signal noise and ensuring accurate vital sign measurements.

What is the significance of the thickness changes in the artery (t-min and t-max) in PPG measurements?

The thickness changes in the artery, from t-min (minimum thickness) to t-max (maximum thickness), are significant as they reflect the cardiac cycle's impact on blood flow, which is essential for accurate PPG measurements.

Outlines

00:00

📡 Understanding PPG Technology

The script introduces Photoplethysmography (PPG) technology, which is used to measure vital signs by shining light into the skin and detecting the light that is reflected back. It explains the process of how an LED shines light into the skin, particularly the finger for a ring device, and how the light interacts with the arteries carrying blood. The diameter of the artery changes dynamically with each heartbeat, creating an oscillating response. A photodetector captures this oscillation and converts it into an electrical signal, which is the PPG signal. This signal is then processed by an application on a phone to provide data such as heart rate, which is essentially the frequency of the PPG signal. The technology behind the ear string is highlighted as a constellation of sensors that can address issues related to the reliability of the PPG signal.

05:01

🌡️ Extracting Vitals from PPG

This paragraph elaborates on the capabilities of PPG technology to extract various vital signs from the PPG signal. It mentions that the PPG signal can be translated into heart rate, blood pressure, breathing rate, and the percentage of oxygen in the blood. The script emphasizes that these vitals are directly extractable from the PPG signal, showcasing the technology's potential for health monitoring and tracking.

Keywords

💡PPG (Photoplethysmography)

PPG stands for Photoplethysmography, a non-invasive optical technique used to measure blood flow and vital signs by shining light on the skin. In the video, it's explained that PPG is fundamental to the technology behind the ring device, as it helps assess heart rate, oxygen saturation, and other vital signs by detecting changes in light reflected from the blood vessels in the skin.

💡Optoelectronic Components

Optoelectronic components are devices that either emit or detect light. In the video, the LED and the photodetector are highlighted as key optoelectronic components in the PPG system. The LED shines light on the skin, and the photodetector captures the reflected light, which changes based on the blood flow through the arteries.

💡Heart Rate

Heart rate refers to the number of heartbeats per minute (BPM). The video explains how the PPG signal is processed by the ring device to calculate heart rate. As blood pulses through the arteries with each heartbeat, the reflected light detected by the photodetector oscillates, allowing the system to measure heart rate.

💡Arteries

Arteries are blood vessels that carry oxygenated blood from the heart to the rest of the body. In the video, the diameter of arteries is described as changing in response to the heart’s pumping action, which affects how much light is absorbed and reflected, thus forming the core of the PPG signal.

💡Photons

Photons are the elementary particles that carry light. In the context of the video, photons from the LED interact with the skin and blood vessels. These interactions, as the heart pumps blood, lead to variations in the reflected photons, which are then detected to generate a PPG signal.

💡AC Response

An AC response refers to an alternating current signal, which in this context describes how the thickness of the arteries changes rhythmically with each heartbeat. The video mentions that this oscillating change in artery size is what leads to the fluctuations in the PPG signal, which is used to assess various vital signs.

💡Diastolic Phase

The diastolic phase is the part of the heart cycle when the heart relaxes and refills with blood. In the video, it is explained that this phase corresponds to the minimum thickness of the arteries, and it is identified in the PPG signal as the lowest point, providing insights into cardiovascular health.

💡Systolic Phase

The systolic phase is the part of the heart cycle when the heart contracts and pumps blood. The video explains that during this phase, the arteries reach their maximum thickness as blood pressure rises, which is reflected in the PPG signal as the highest peak.

💡Heart Rate Variability (HRV)

Heart rate variability (HRV) refers to the variation in time between consecutive heartbeats. In the video, HRV is mentioned as one of the metrics calculated from the PPG signal. It provides important insights into the body’s stress levels and overall cardiovascular health.

💡Blood Oxygen Saturation (SpO2)

Blood oxygen saturation (SpO2) measures the percentage of oxygen-saturated hemoglobin in the blood. The video mentions SpO2 as one of the vital signs that can be measured using PPG technology, providing information about how efficiently oxygen is being transported throughout the body.

Highlights

Introduction to PPG technology and its application in Kickstarter campaign.

PPG stands for photoplethysmography, a non-invasive electronic-based technology for assessing vital signs.

PPG technology works by shining light into the skin and measuring the reflected light.

The interaction of light with the skin's arteries is crucial for PPG signal generation.

Arterial diameter changes dynamically with each heartbeat, affecting the PPG signal.

The PPG signal is an AC oscillating frequency that corresponds to the heart's systolic and diastolic phases.

The photodetector captures reflected light and converts it into an electrical PPG signal.

The PPG signal's frequency is directly related to the heart rate.

The application on the phone processes the PPG signal into heart rate and other vital signs.

The constellation of sensors in the ear string helps address reliability issues of the PPG signal.

The technology embedded in the ear string can extract various vitals, including blood pressure.

The ear string's design allows for a more reliable PPG signal due to its positioning.

The oscillating diameter of the artery is key to understanding the PPG signal's formation.

The PPG signal's maximum corresponds to the diastolic phase, and minimum to the systolic phase.

The frequency of the PPG signal can be translated into heart rate variability (HRV) data.

The technology can also measure the ability of the pick to pick SP2 in percentage of oxygen breathing rate.

The campaign aims to demonstrate how the PPG technology can be improved with multiple sensors.

Nino's demonstration will show how the PPG works and how issues can be addressed with the ear string technology.

Transcripts

hi there since we launched the campaign

on Kickstarter we have received a lot of

questions around the PPG technology how

it works the issues related to the

reliability of the PPG signal and how

our technology and especially our

constellation of sensors all around the

brain can help solving all of these

issues so today Nino is going to show us

a description of how the PPG works and

how we can address those different

issues using the technology that we

embedded in the air string let's go

let's see together how the PPG work how

the technology which is behind the ear

string works first of all PPG stands for

photoplatismography which is a not to

electronic based technology and Men of

assessing several vital signs but but

just shining life in the skin so let's

see together how this works first of all

we start with the not electronic

components so an LED which is Shining

Light suppose this light is great

so the light so the photons which are

actually the particles which are

carrying the light will be

interacting with the skin in this case

the finger since we're talking about the

ring device

the skin so the finger consists of a lot

of things including fat muscles but

particularly the arteries that are

actually carrying the blood which is

pushed by the heart throughout the whole

body what happens is that in Phase with

the heart pumping with the cardiac

activity the diameter of this artery

here changes dynamically adapts over the

time so suppose that we call this

thickness here so this section this

diameter of the artery which we call it

t-min which is minimum thickness

that one big pressure wave comes from

the heart what happens is that it will

see a blast of blood that will be

actually propagating through the artery

and then eventually the size the

thickness of this artery will be

changing will be moving from timing to

what we call T-Max so if we display this

over the time this means the following

so we can actually have pmax here team

in here and this which is maximum

thickness minimum thickness this is

actually a Time

in face with the heart pumping basically

this thickness this diameter will be

following an AC response not sledding

response

so now let's see how this oscillating

response moves and builds up basically

the people you think that's thanks to a

second optoelectronic component which is

called the photo detector which is a not

Electronic Component that is basically

receiving the light so these photons

that have interacted with the finger

including this oscillating diameter and

the bars of blood and are basically

reflected back

so the photo detector is basically

capturing these photons and converting

them into an electrical signal which is

exactly the PPG signal that is processed

by the application which is running on

your phone so it would be a signal that

will be basically an AC oscillating

frequency whose

maximum year corresponds to what is

called the diastolic phase of the arc

which is corresponding to the minimum

thickness of the arteries

minimum corresponds to the systolic

phase of the heart which is basically

corresponding to the to the largest

pressure wave coming from the heart

this signal which is called the PPG has

a given frequency that let's call it f

PPG which is nothing

more than just a heart rate suppose that

this frequency is one Hertz

okay this corresponds to what is called

60 BPM 60 bits per minute which is the

physiological cardiac frequency of every

individual but how do we get there we

get there thanks to the algo so you have

actually your you basically

download the data from The Ring to your

phone via the application that's called

suppose this is actually the phone

the phone the applications will be

basically doing this will be translating

the signal into what into hard trade

data 60 bits per minutes into HRV data

suppose 60 milliseconds for the ability

of this pick to pick

SP2

in percentage of oxygen breathing rate

and all the vitals including blood

pressure which are directly extractable

out of the PPG