The influence of yoga exercises with voluntary pulmonary ventilation changes on intracranial arterial blood flow

Introduction. Yoga breathing exercises that involve voluntary changes in pulmonary ventilation parameters can potentially influence cerebral circulation due to changes in CO2 content in arterial blood. Objective. To assess the effect of yoga breathing exercises with changes in pulmonary ventilation levels on blood flow parameters in the middle cerebral artery (MCA). Methods. The study included 21 participants, with an average age of 39.5±8.7 years, who were capable of performing yoga exercises at respiratory rates (RR) of 3–3.5/min and 1–1.5/min. For 5 minutes, participants underwent three stages: free breathing (stage 1), breathing with RR=3–3.5/min (stage 2), and breathing with RR=1–1.5/min (stage 3). During stages 2 and 3, the «full breathing» technique, which involves maximum deep inhalation and exhalation, was employed. Respiratory rate (RR), tidal volume (TI), minute ventilation (MV), end-tidal CO2 partial pressure (PetCO2), and oxygen fraction in exhaled air (FeO2) were recorded using spiro-gas analysis. Transcranial duplex scanning was used to measure peak systolic blood flow velocity (Vps), end-diastolic blood flow velocity (Vd), time-averaged maximum blood flow velocity (TAMAX), and resistance index (RI) in the right MCA. The velocity variation index (VVI) was calculated for each stage. Results. Compared to stage 1 (free breathing), stage 2 (RR = 3–3.5/min) showed an increase in MV and FeO2, a decrease in PetCO2, and reductions in Vps, Vd, and TAMAX, with an increase in RI. VVI decreased statistically insignificantly. In stage 3 (RR = 1–1.5/min), compared to stage 1, there was an increase in PetCO2, a decrease in MV and FeO2, and increases in Vps, Vd, and TAMAX, with a decrease in RI. VVI increased significantly. Conclusions. Yoga breathing exercises at respiratory rates of 3–3.5/min and 1–1.5/min result in multidirectional shifts in ventilation and gas exchange parameters, leading to changes in arterial cerebral blood flow (a decrease and increase in blood flow velocity with an increase and decrease in MV, respectively). VVI, reflecting fluctuations in blood flow velocity, increases significantly with reduced MV, likely due to the vasodilatory effect of CO2.