The research team from Russia proposed a new contactless method for measuring blood flow in the upper limbs. The method is based on a video recording of the skin surface under green light measuring the absorption of red blood cells.

Este helps to see how effective circulatory system and the blood flow regulation are. The experimental results showed that the method is not inferior in accuracy to the traditional one. However, it is easier to use, cheaper and fits more patients. The work was published in  Biomedical Optics Express.

Measuring blood flow in the limbs is an important diagnostic indicator. By studying how effectively the heart supplies blood to the limbs, we can see if the cardiovascular system works well and if the blood flow is regulated effectively.

Today, scientists usually use contact (or potentiometric) methods of occlusive plethysmography to measure blood flow in the limbs. Such an approach is based on recording changes in the volume or diameter of to limb due to its filling with blood during venous occlusion.

The blood flow

A way of affecting the blood flow, occlusion happens when venous outflow is stopped by applying a slight pressure on the arm without interrupting the arteries. As a result, it is possible to determine the blood flow equal to the increase in the volume of the limb due to the blood flow from the heart.

However, contact measurement systems are difficult to configure and use. In addition, such methods are expensive and require adaptation for each new patient. To overcome the limitations of standard methods, scientists from ITMO University and Almazov National Medical Research Center developed a contactless system for measuring blood flow in the upper limbs.

Item is based on photoplethysmography. This technique is capable of tracking changes in the blood supply of the skin using a video recording of the absorption of green light. When green light hits red blood cell, the reflected wave changes its polarization.

The camera registers only this modified signal and tracks when it gets most intense. The reason for the increase in light absorption during venous occlusion can be explained by the increase in the number of red blood cells, most likely due to the expansion of the small veins of the upper layer of the skin.

To assess the accuracy of measurements using the new system, scientists conducted a series of experiments and compared the values? obtained by traditional and new methods. Experimental measurements were performed on healthy volunteers.

The signal was recorded for several cycles of venous occlusion. The results of the cold stress effect on the vessels obtained by a new method almost completely coincided with the results of traditional measurements.