Scientists have proven that their “green flashlight” for blood vessels — a method called imaging photoplethysmography (IPPG) — can peer deep into living tissues and assist in complex medical cases, including surgical operations. The method records pulse changes not only in superficial vessels but also in deep cerebral arteries. The results, supported by a grant from the Russian Science Foundation, have been published in the Frontiers in Physiology.
A research team from the Institute of Automation and Control Processes of the Far Eastern Branch of the Russian Academy of Sciences (Vladivostok), together with colleagues from St. Petersburg — the Northwestern District Scientific and Clinical Center of the FMBA of Russia, the Pavlov Institute of Physiology of the Russian Academy of Sciences, and the First Pavlov State Medical University of St. Petersburg — demonstrated this in studies on laboratory rats.
During the experiments, the scientists used the developed method, which synchronizes video recording of the rat’s brain with an electrocardiogram. The animals were alternately administered two drugs with opposite effects: adenosine triphosphate (ATP), which dilates blood vessels, and norepinephrine, which constricts them. It turned out that the recorded pulse signal changed in the opposite direction to changes in systemic arterial blood pressure.
For example, when ATP was administered, blood pressure dropped, but cerebral blood flow sharply increased — this means that the deep arteries relaxed and the protective mechanism of autoregulation kicked in. When norepinephrine was administered, the picture was the mirror opposite: after a shortterm pressure spike, the cerebral vessels constricted and blood flow decreased, even if high blood pressure persisted.
Thus, the authors have for the first time demonstrated that the non-contact method of imaging photoplethysmography can reflect in real time changes in the tone of deep cerebral arteries that do not coincide with changes in systemic hemodynamics.
«The results obtained have practical significance for medicine. ATP and norepinephrine are widely used in intensive care units and cardiology. A detailed understanding of their effect on cerebral arteries will allow doctors to more precisely adjust dosages and minimize risks associated with insufficient or excessive cerebral blood supply», noted Alexey Kamshilin, a grantee of the Russian Science Foundation, one of the study’s authors, Doctor of Physical and Mathematical Sciences, and Chief Researcher at the Institute of Automation and Control Processes of the Far Eastern Branch of the Russian Academy of Sciences.
The Russian Science Foundation clarified that the method is applicable, for example, to burn patients, in neonatal care, and during surgical operations.
