Blood Volume Pulse (PPG)

A photoplethysmography (PPG) transmits an infrared light through the tissue and measures the absorption of this light by the blood flowing through the vessels. It can be used to sense the rate of blood flow as controlled by the heart beats, also called Blood Volume Pulse (BVP). This is a non-invasive method and can be measured anywhere on the body where a superficial pulse is available. The most common places to measure pulse are the fingers and the earlobes. Every time the heart beats, the PPG detects a peak in this absorption, which is shown as a peak in the pulse. The interval, or distance, between the peaks (the Interbeat Interval (IBI)) defines the heart rate (HR). The amplitude or the height of the pulse defines the measure of relative blood flow: when blood vessels expand (vasodilation), relatively more blood flows through the vessels and the higher the peak in the signal.

During each heartbeat, the heart contracts and blood flows as a pulse through the arteries and blood vessels. The Blood Volume Pulse sensor shows this pulse as a result of this. Blood Volume Pulse (BVP) is a non-invasive method and can be measured anywhere on the body where a superficial pulse is available. The most common places to measure BVP are the fingers and the earlobes.  The latter can e.g. be done by using the BVP Head Sensor.

The BVP sensor transmits an infrared light through the tissue and measures the absorption of this light by the blood flowing through the vessels. Every time the heart beats, the sensor detects a peak in this absorption, which is shown as a peak in the BVP signal (pulse). The interval, or distance, between the peaks (the Interbeat Interval (IBI)) defines the heart rate (HR) (See the figure, A). The amplitude or the height of the pulse defines the measure of relative blood flow: when blood vessels expand (vasodilation), relatively more blood flows through the vessels and the higher the peak in the BVP signal.

Equipment for measuring BVP