Cardiovascular and respiratory effect of yogic slow breathing in the yoga beginner: what is the best approach?

Slow breathing increases cardiac-vagal baroreflex sensitivity (BRS), improves oxygen saturation, lowers blood pressure, and reduces anxiety. Within the yoga tradition slow breathing is often paired with a contraction of the glottis muscles. This resistance breath "ujjayi" is performed at various rates and ratios of inspiration/expiration. To test whether ujjayi had additional positive effects to slow breathing, we compared BRS and ventilatory control under different breathing patterns (equal/unequal inspiration/expiration at 6 breath/min, with/without ujjayi), in 17 yoga-naive young healthy participants. BRS increased with slow breathing techniques with or without expiratory ujjayi (P < 0.05 or higher) except with inspiratory + expiratory ujjayi. The maximal increase in BRS and decrease in blood pressure were found in slow breathing with equal inspiration and expiration. This corresponded with a significant improvement in oxygen saturation without increase in heart rate and ventilation. Ujjayi showed similar increase in oxygen saturation but slightly lesser improvement in baroreflex sensitivity with no change in blood pressure. The slow breathing with equal inspiration and expiration seems the best technique for improving baroreflex sensitivity in yoga-naive subjects. The effects of ujjayi seems dependent on increased intrathoracic pressure that requires greater effort than normal slow breathing.

Arterial baroreflex modulation influences postural sway.

OBJECTIVE: Although considered mainly a random function, postural sway is influenced by physiological factors such as respiration. A direct effect of the autonomic nervous system (ANS) on posture has never been demonstrated. To test this hypothesis, we used a pure motion-independent autonomic stimulus (neck suction) to modulate the carotid baroreceptors on a broad frequency range, distinct from that of respiration. METHODS: Thirteen healthy subjects (age 26 ± 5 years) were studied upright, eyes closed, and on a force platform during controlled breathing (15 breath/min, 0.25 Hz), with and without stimulation of arterial baroreceptors by sinusoidal neck suction (0 to -30 mmHg pressure) at different frequencies (0.05, 0.10, 0.125, 0.15, 0.175, 0.20, 0.30 Hz), for eight periods lasting 2 min each. The increase in sway, R-R interval and blood pressure induced at each stimulation frequency was measured by spectral analysis. RESULTS: With neck suction, we observed a significant (p < 0.05) increase in oscillations synchronous in the R-R interval (from 0.10 to 0.20 Hz), systolic and diastolic blood pressure (from 0.05 to 0.15 Hz) and sway (from 0.10 to 0.30 Hz in both the antero-posterior and medio-lateral planes). Changes were greater in the left than in the right foot. CONCLUSION: Our study shows that postural sway is modulated by the ANS and is influenced by phasic stimulation of the arterial (carotid) baroreceptors. Our findings have potentially important clinical implications in the development of treatment strategies for pathological conditions in which alterations in posture and autonomic function coexist and could be mutually influenced.