Blood oxygen sensors in watches work by shining light into your skin and measuring how much light is absorbed by your blood. This allows the watch to estimate the percentage of oxygen in your blood.
The Science Behind It
Oxygen sensors on watches rely on a principle called pulse oximetry. Here's a breakdown:
- Light Emission: The watch emits red and infrared light.
- Absorption Differences: Haemoglobin, the protein in red blood cells that carries oxygen, absorbs different amounts of red and infrared light depending on how much oxygen it's carrying. Oxygen-rich haemoglobin (oxyhemoglobin) absorbs more infrared light and allows more red light to pass through. Deoxygenated haemoglobin absorbs more red light and allows more infrared light to pass through.
- Detection and Calculation: A sensor in the watch detects the amount of red and infrared light that passes through your blood vessels. By comparing the absorption rates of these two types of light, the watch calculates the percentage of oxygen saturation in your blood (SpO2).
- Display: The watch then displays this percentage as a numerical reading.
Accuracy Considerations
While convenient, it's important to understand that the accuracy of blood oxygen sensors on watches can be affected by several factors:
- Skin Tone: Some studies suggest potential inaccuracies in individuals with darker skin tones.
- Movement: Excessive movement during the reading can interfere with the sensor's ability to accurately measure light absorption.
- Fit: The watch needs to fit snugly against your skin to ensure proper contact and prevent ambient light from interfering with the readings.
- Perfusion: Poor blood flow to the wrist area can affect accuracy.
- Medical Conditions: Certain medical conditions can influence blood oxygen levels and sensor readings.
- Ambient Light: External light sources can sometimes interfere with the readings.
Intended Use
It's crucial to remember that smartwatches with blood oxygen sensors are typically designed for general wellness monitoring and not as medical devices. Always consult with a healthcare professional for accurate diagnoses and treatment plans related to oxygen levels or any health concerns.
