Normal Breathing Pattern and Body Oxygenation
”The perfect man breathes as if he is not breathing” Lao Tze (604 - c.521 BC), Chinese Philosopher
If you have healthy friends or relatives, you can easily observe that their breathing is regular, nasal only, diaphragmatic, invisible or shallow (no chest or belly movements), and inaudible (no panting, no wheezing, no sighing, no yawning, no sneezing, no coughing, no deep inhalations or exhalations). They take small inhalations and then relax for the exhalation. The exhalation is followed by an automatic pause (or period of no breathing) of about 2 s. The usual CP (Control Pause) or body oxygenation index of healthy people is about 40 s for the medical norm and 60 s for the Buteyko norm.
The durations of inhalations and exhalations, breathing rate, amount of air inhaled per breath and other parameters are individual. Many healthy people can have the following parameters of the breathing cycle: inhalation (about 1.5-2 s); exhalation (1.5-2 s); automatic pause of almost no breathing (2 s); the depth of inhalation is about 500-600 ml; and breathing frequency (or Rf - respiratory frequency) is about 10-12 breaths/min. The international physiological norm for the breathing rate is 6 l/min (for a 70-kg man). References for medical textbooks that provide these values are below.
This picture shows 4 breathing cycles of normal breathing: inhalation (the upward lines), exhalation (the downward lines) and automatic pause (the almost horizontal lines) accompanied by relaxation of all breathing muscles.
As mentioned above, the person with such breathing is going to have about 40 s CP. This indicates good oxygenation of tissues and cells due to normal oxygen transport. Most of the job of inhalation (up to 80-90%) is done by the diaphragm, the main breathing muscle. Exhalation is passive and accompanied by relaxation of all breathing muscles.
Medical textbooks references
Ganong WF, Review of medical physiology, 15-th ed., 1995, Prentice Hall Int., London.
Guyton AC, Physiology of the human body, 6-th ed., 1984, Suanders College Publ., Philadelphia.
McArdle W.D., Katch F.I., Katch V.L., Essentials of exercise physiology (2-nd edition); Lippincott, Williams and Wilkins, London 2000.
Straub NC, Section V, The Respiratory System, in Physiology, eds. RM Berne & MN Levy, 4-th edition, Mosby, St. Louis, 1998.
Summary of values useful in pulmonary physiology: man. Section:
Respiration and Circulation, ed. by P.L. Altman & D.S. Dittmer, 1971,
Bethesda, Maryland (Federation of American Societies for Experimental
Biology).