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.