Russian scientists have experimentally confirmed the possibility of non-contact monitoring of blood flow in the deep arteries of the brain — an area previously considered inaccessible to such methods. This opens up new opportunities for diagnosing and monitoring patients' condition in real time without the use of invasive technologies.
Such Opportunities Remained in Question for a Long Time
Previously, scientists were not sure what exactly the method of visualizing photoplethysmography (VPPG) shows — a technology that uses light to analyze blood flow without contact with the body. It was believed that it only recorded changes in superficial vessels, that is, the movement of blood directly under the skin.
Now this view has changed. The new work is the first to experimentally prove that the method captures pulsation precisely in the deep arteries of the brain, and not only on the surface. The results are published in the journal Frontiers in Physiology.
How the Experiment Was Conducted
The study was conducted by a scientific team from the Institute of Automation and Control Processes of the Far Eastern Branch of the Russian Academy of Sciences, the North-Western District Scientific and Clinical Center of the Federal Medical-Biological Agency of Russia, the I.P. Pavlov Institute of Physiology of the Russian Academy of Sciences, and the First St. Petersburg State Medical University named after I.P. Pavlov.
Experiments were carried out on laboratory animals — rats. Scientists used a developed VPPG system with synchronization of video recording and electrocardiogram.
The animals were alternately injected with two drugs with opposite effects. Adenosine triphosphate dilates blood vessels, while norepinephrine, on the contrary, constricts them.
What the Scientists Saw
The results were indicative. The VPPG pulse signal changed oppositely to changes in systemic arterial pressure.
When ATP was injected, the pressure decreased, but blood flow in the brain increased sharply. This meant that the deep arteries relaxed and the autoregulation mechanism was activated.
When norepinephrine was administered, the opposite picture was observed. After a short-term increase in pressure, the brain vessels narrowed, and blood flow decreased, even if the pressure remained high.
The results have practical significance. ATP and norepinephrine are widely used in intensive care and cardiology. Understanding their effect on brain vessels will allow doctors to more accurately select dosages and reduce the risks associated with insufficient or excessive blood supply.
