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Pranayam and the Mechanism of Respiration

The process of inhaling Pranashakti (Energy associated with Prana) and exhaling it out is called Pranayama. This Pranashakti can be achieved through the control of respiration. There are certain functions of the human body which are both voluntary and involuntary. 

For example the action of the heart, the movements of the stomach and the intestines are involuntarily influenced by emotions and are normally beyond voluntary control. We cannot stop or modify them at will. The excretion of urine and faeces on the other hand is partly voluntary and partly involuntary. 

One gets the urge for passing urine or stool, but we can still control it through willpower. In the same way the act of respiration and the process of thinking and emotion are also both voluntary and involuntary. It is the movement of lungs that produce the breath and it is the Prana that moves the lungs. By diligently practicing the nerves and the muscles that control the process of breathing, it can be controlled at will. So Pranayama means not control of breath but the control of the energy or force that controls the breath.



LUNG VOLUMES AND CAPACITIES

• The tidal volume (TV), about 500 ml, is the amount of air inspired during normal relaxed breathing.

• The inspiratory reserve volume (IRV), about 3,100 ml, is the additional air that can be forcibly inhaled after the inspiration of a normal tidal volume.

• The expiratory reserve volume (ERV), about 1,200 ml, is the additional air that can be forcibly exhaled after the expiration of a normal tidal volume.

• Residual volume (RV), about 1,200 ml, is the volume of air still remaining in the lungs after the expiratory reserve volume is exhaled.

SUMMING SPECIFIC LUNG VOLUMES AND THE LUNG CAPACITIES:

• The total lung capacity (TLC), about 6,000 ml, is the maximum amount of air that can fill the lungs (TLC = TV + IRV + ERV + RV).

• The vital capacity (VC), about 4,800 ml, is the total amount or air that can be expired after fully inhaling (VC = TV + IRV + ERV = approximately 80% TLC).

• The inspiratory capacity (IC), about 3,600 ml, is the maximum amount of air that can be inspired (IC = TV + IRV).

• The functional residual capacity (FRC), about 2,400 ml, is the amount of air remaining in the lungs after a normal expiration (FRC = RV + ERV).

• Some of the air in the lungs does not participate in gas exchange (150ml). Such air is located in the anatomical dead space within bronchi and bronchioles—that is, outside the alveoli.

• The instrument that is used to measure the volume of air inspired and expired by the lungs is called spirometer.

MUSCLES INVOLVED IN BREATHING

The main muscle of respiration is the diaphragm. Other muscles that aid in respiration include the external intercostals, scalenes, sternomastoids, abdominal muscles and internal intercostals.

Diaphragm
In quiet, gentle inhalation, the diaphragm contracts, lowering air pressure inside the lungs and drawing air in. When exhaling quietly, the diaphragm relaxes and the pressure reverses, expelling air.

External Intercostals
The external intercostals are in between the ribs. During active inhalation, they expand the rib cage laterally, anteriorly and posteriorly.

Scalenes/Sternomastoids
These are the shrugging muscles. They serve to lift the sternum and the upper ribs during active inhalation.

Abdominal Wall
In active exhalation, the muscles of the abdominal wall--rectus abdominis, internal and external obliques and transverse abdominis--contract, raising abdominal pressure. This, in turn, raises the diaphragm, raising pressure in the lungs and expelling air.

Internal Intercostals
The internal intercostals are deep to the external intercostals. Like their counterparts, they draw the ribs in, expelling air during active exhalation.

VERTICAL BREATHING (DIAPHRAGM BREATHING)

The vertical breathing is called diaphragmatic breathing and is considered a more efficient way to inhale air. It is also called Yogic breathing. Yogic breathing is more a vertical breathing than horizontal breathing. By this vertical breathing all the alveoli (the functional units of lungs) of both the lungs open out evenly. Due to the even expansion of all the alveoli, a vast expanse of alveolar membrane is available for exchange of gases. There are totally about 700 million alveoli in the two lungs of an adult human being. This effect is more obvious in the apical, central and basal alveoli. This surface is about 50 square meters in extent, which is 20 times the entire body surface. The larger the surface available for the process of diffusion, the better would be the process of breathing.

HORIZONTAL BREATHING

In horizontal breathing, the alveoli toward the periphery expand more than optimum, while the centrally placed alveoli do not open out properly. This affords a lesser and uneven surface for diffusion of gases. If some alveoli remain unopened, they get stuck. There is a collection of secretion in them and they are prone to disease formation. Moreover, if the peripheral alveoli open wider than is preferable, they lose their elasticity. 

The interalveolar walls (The wall, which unites as well as separates two contiguous pulmonary alveoli) may be broken, damaging the capillaries and leading to diseases like emphysema or pulmonale. (Capillaries are the smallest of blood vessels. They serve to distribute oxygenated blood from arteries to the tissues of the body and then feed deoxygenated blood from the tissues back into the veins).

PRANAYAMAS

Anulom-viloma (alternate nostrils), Ujjayi, Sheetali and Sheetkari Pranayamas promote vertical breathing. In all these Pranayamas we have seen that inspiration is done slowly and deeply as much as possible. When we take the breath in, the lungs are expanded considerably and walls of the alveoli are stretched maximum. Therefore the alveoli in the upper pulmonary part are filled with air completely.

This has a beneficial effect on the gaseous exchange which then works efficiently throughout the day. When we breathe out slowly through one nostril only (as in Ujjayi or Anulom-viloma) or through both the nostrils by contracting the glottis partially at the same time (another variety of Ujjayi) the exhalatory force is reduced and the air is allowed to escape slowly. This helps in prolonging the exhalation and to reduce the force of the outgoing air.

To feel the pressure of the inspired air in the lungs and to experience the stillness of the mind during retention or emptiness of the lungs while exhaling, one should do Pranayamas with concentration and awareness. In short, during the practice of Pranayama one tackles all the respiratory reflexes on account of our volitional control on the respiration.


Courtesy: Dr. Rita Khanna

Aum Shanti