Cerebrovascular dynamics associated with yoga breathing and breath awareness

Aims: Breath frequency can alter cerebral blood flow. The study aimed to determine bilateral middle cerebral arterial hemodynamics in high-frequency yoga breathing (HFYB) and slow frequency alternate nostril yoga breathing (ANYB) using transcranial Doppler sonography. Methods: Healthy male volunteers were assessed in two separate trials before, during, and after HFYB (2.0 Hz for 1 min, n = 16) and ANYB (12 breaths per minute for 5 min, n = 22). HFYB and ANYB were separately compared to breath awareness (BAW) and to control sessions. Statistical Analysis: The data were analyzed using repeated-measures ANOVA with Bonferroni adjusted post hoc tests. Results: During HFYB there was a decrease in end-diastolic velocity (EDV) and mean flow velocity (MFV) (P < 0.01 for left and P < 0.05 for right middle cerebral arteries; MCA) with an increase in pulsatility index (PI) for the right MCA (P < 0.05). During ANYB, there was a bilateral decrease in peak systolic velocity (P < 0.05 for left and P < 0.01 for right MCA), EDV (P < 0.01) and MFV (P < 0.01 for left and P < 0.001 for right MCA) and an increase in PI (P < 0.01). During BAW of the two sessions there was a decrease in lateralized flow and end-diastolic velocities (P < 0.05) and an increase in PI (P < 0.05). Conclusions: Changes in peak flow velocities and pulsatility indices during and after HFYB, ANYB, and BAW suggest decreased cerebrovascular blood flow and increased flow resistance based on different mechanisms.