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Respiratory control: In normal circumstances, nervous control is unconscious. One does not have to think about when to inhale or exhale. However, by changing the pattern of the breath, one can learn to manoeuvre the autonomic nervous system and higher brain function, or in yogic terms, the ida, pingala and sushumna nadis. In other words, by changing the breath pattern one can induce a chosen state of mind. Even though unhealthy breathing habits are likely to be insidious, it is possible to change them because the respiratory motions are controlled by somatic motor neurons. Therefore, it is possible to think the actions of respiration through and control them wilfully.
The ventilation rate of the lungs is normally set to provide oxygen and remove carbon dioxide in accordance with metabolic needs. A better air flow or ventilation of the lungs can be achieved with a slow breathing rate and large tidal volume or fast rate and small tidal volume. When this is achieved though controlled practice, bringing about deep and slow rhythmic respiratory patterns, and changing the habits of faulty breathing, elimination of waste gases is improved, the heart and circulatory functions are regulated and arrhythmic heart beat is rectified. All these induce a sense of relaxation throughout the body-mind complex.
In the practice of nadi shodhana pranayama, when the length of breath is extended from two or three seconds to seven or eight seconds and the air is held longer in the lungs, there is an increased potential for greater gaseous absorption, separation and elimination in the lungs. In the normal breath we find, say, 3.5 mg absorption of oxygen and an output of 2.6 mg of carbon dioxide. In simple regulated breath control practices this ratio can be improved, so that the output of carbon dioxide level is increased to 4.6 mg, that is, almost double the average norm, depending on the technique employed.
It has been found that if the carbon dioxide level in the blood decreases through improved elimination of carbon dioxide, the normal respiratory rate becomes slower. This
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