Taking it for granted that breathing means living, and viceversa, one may still wonder why life is so dependent on breathing, and why it comes to an end when breathing becomes impossible. All of us know that we cannot live without air. But very few of us are in a position to say why this is so. It would be very helpful to be aware of the processes involved In breathing in order to understand how pranayama can be used for the prevention and cure of disorders.
To begin with we must differentiate between breathing and respiration. In common usage these two terms are often used as synonyms. But actually respiration is a wider term. Breathing is a physical or mechanical act performed with the help of specialized organs, in which air, or more specifically, oxygen from the air enters the body, and then the air together with the impurities from the body such. as Carbon dioxide and water vapour, is drawn out of the body. Respiration, as a wider term, includes this act as well as the further process of carrying the absorbed oxygen to every part of the body and distributing it throughout the body. In case of man and higher animals we may say that they breathe as well as respire. But in case of plants, lower forms of life, and microorganisms, there is only respiration and no breathing, because there are no organs for breathing. A new-born baby starts breathing just after birth when the lungs are filled with air for the first time. Before birth, in the womb of its mother it does not breathe, but respiration still exists, and oxygen is supplied to each cell of its growing body inside the womb.
Now let us see why oxygen is indispensable for life. Every living tissue and cell requires a constant supply of energy to live. To be alive means to undergo certain bio chemical processes. These processes which are the essence of life cannot go on without energy. This energy is stored in the molecules of certain substances such as glucose, fructose, fatty acids, and amino acids. These molecules are the end products of the process of digestion of food materials which we eat. The energy stored in these molecules can be released from them only through a chemical interaction called oxidation of the energy containing compounds, which cannot take place without oxygen. In the absence of oxygen the process of release of energy comes to a halt, which means the death of that tissue. Oxygen is already present in the atmosphere on earth. At sea level there is about 20% oxygen in the air. This oxygen cannot be utilized by the cells and tissues of our body directly from the atmosphere. It has to be carried to each cell and tissue. This important job of carrying oxygen to each minute part of the body is done for us by the blood. This is called internal respiration. The task of bringing oxygen in contact with the blood is called external respiration. It is the same thin" as breathing. Thus breathing may be called the outer expression of the process of internal respiration. Thus if breathing stops, then each cell and tissue of the body which requires oxygen continuously for keeping on the process of oxidation in order to release energy stored in the end products of carbohydrates, fats, and proteins, would be starved of oxygen. Lack of oxygen means no further oxidation, which means no supply of energy for the big-chemical process of living, and that inevitably results in the death of that cell or tissue. That is why life is solely dependent on breathing. This was perhaps the reason why our ancestors used the word prana both for the air we breathe and for the essence of life, namely, the soul. But even if it is true that breathing is so vital for life, one may still wonder whether there is any advantage in controlling the breath. That is our next question.