What is Photo­plethysmo­graphy (PPG)?

Vital values can be measured in different ways. In the hospital, nurses normally do this at the bedside three times a day. In the home situation, patients can take a measurement themselves a few times a day with all sorts of separate devices. The results you get are so-called 'spot measurements': snapshots of the vital values. These can then be sent to a platform via a mobile app.

viQtor does this differently. The vital values are measured continuously on the upper arm, simple and very accurate. This measurement is done with the sensor technology of viQtor via photoplethysmography, abbreviated PPG. This technique has been used for decades to measure changes in blood circulation. PPG is a non-invasive technique; that is, no instruments are inserted into the body. You don't notice or feel anything.

How does PPG work?

PPG measures the changes in blood volume in the veins. We use different types of light for this: red, green and infrared LED light. The light from these LEDs is sent through the skin. The tissues and blood absorb part of the light and reflect another part back to the light-detection sensors on the skin. The light received by the sensors is converted into an electrical signal. This is then filtered and amplified.

The amount of blood flowing through the veins and capillaries varies with your heart rate. With each heartbeat, blood is pushed through the blood vessels. If there is more blood in the vessels, more light is absorbed. The light sensors then receive less light.

What can we measure?

Based on this variation in blood volume, viQtor can determine the heart rate or heart rate (HR). Because PPG does not measure the electrical activity of the heart (like an ECG) but changes in blood volume, the signal you get looks different: the graph has a waveform. With PPG we can also measure other vital values, such as the oxygen content of the blood, the respiratory rate and the blood pressure.

The average of the measurements is calculated using smart algorithms. Every five minutes this is forwarded to our platform in the cloud. The measurements are analyzed on this platform and then stored securely and pseudonymised. The platform is linked to an online dashboard and an app. Healthcare professionals and informal carers can consult the information there.