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The fainting and light-headedness arise for two reasons: firstly, pressure on the blood vessels in the neck causes fluctuations in the pressure within the cranial cavity, and secondly, the carotid sinuses, vital to maintaining autonomic control of the body's circulation, are continuously compressed, changing the tone of the autonomic nervous system and inducing a swooning sensation. The practice of kumbhaka further reduces the oxygen supply to the brain, especially if held for a long time.
SURYA BHEDA PRANAYAMA
Surya Bheda Pranayama (vitality stimulating breath)
Assume a comfortable meditation asana with the head and spine straight. Place the hands on the knees in either chin or jnana mudra. Close the eyes and relax the whole body. When the body is comfortable, still and relaxed, watch the breath for a few minutes until it spontaneously becomes slow and deep. Adopt nasagra mudra (see nadi shodhana pranayama). Close the left nostril with the ring finger and inhale slowly and deeply through the right nostril. At the end of inhalation close both nostrils, retain the breath and perform jalandhara and moola bandhas. Maintain for just a few seconds when first practising this pranayama. Release moola bandha and then jalandhara bandha. When the head is upright once more, exhale slowly through the right nostril by keeping the left nostril closed with the ring finger.
This is one round. Awareness: On the breath and mechanics of the practice.
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