Neuro-cardiovascular correlates of controlled slow yogic breathing: A pilot study

Abstract

Objectives: We assessed the frontal cerebral hemodynamic alterations and neuro-cardiovascular interactions during alternate nostril breathing (ANB), a slow yogic breathing manoeuvre. Materials and Methods: Five healthy male volunteers (age 30 ± 3.8 years) practised ANB for 5 min at five breaths per minute with the timing ratio (seconds) of 4:2:4:2 (inspiration: Pause: Expiration: Pause). We recorded 16 channels of functional near-infrared spectroscopy at the prefrontal cortex (PFC) region of the brain, electrocardiography, beat-to-beat arterial blood pressure (BP), respiratory movements and end-tidal carbon dioxide (ETCO2) for 5 min each: Pre (T0), during (T1) and post-ANB (T2). ETCO2, oxy-haemoglobin (oxy-Hb), deoxy-haemoglobin (deoxy-Hb), total haemoglobin (HbT) concentrations and time domain parameters of heart rate variability (HRV), BP variability (BPV) and baroreflex sensitivity (BRS) were calculated. Results: In comparison to T0, the oxy-Hb and time domain parameters of HRV and BPV at the left lower region of the PFC were significantly increased at T1. Up-BRS-SBP showed a trend of enhancement during the manoeuvre. A significant optically measured HbT concentration with a corresponding decrease in deoxy-Hb was observed at T1. Conclusion: Optically measured Oxy-Hb and HbT increased gradually with the increased practice of ANB, with a simultaneous decrease in deoxy-Hb suggesting a cerebral activation during ANB that may be predominantly in ventromedial PFC. Both baroreflex and mechanical mechanisms appear responsible for the improved neurovascular coupling. Slow yogic breathing may have beneficial effects in disorders that involve cerebral hypoactivation.