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Normal breathing, as we discussed, is strictly nasal (in and out), mainly diaphragmatic (i.e., abdominal), slow (in frequency) and imperceptible.
The physiological norm for minute ventilation at rest is 6 litres per minute for
a 70 kg man (see references for textbooks below: Guyton, 1984; Ganong, 1995;
Straub, 1998; Castro, 2000; etc.). These medical textbooks also provide the following
parameters of normal breathing:
- normal tidal volume (air volume breathed in during a single breath): 500 ml;
- normal breathing frequency: 12 breaths per minute;
- normal inspiration: about 2 seconds;
- normal exhalation is 2-3 seconds.
The following graph represents the normal breathing pattern at rest or the dynamic of the lungs' volume as a function of time:
“If a person breath-holds after a normal exhalation, it takes about 40 seconds before breathing commences” (McArdle et al, 2000). This indicates normal oxygenation of tissues.
The current medical norm for CO2 content in the alveoli of the lungs and the arterial blood is 40 mm Hg CO2. This number was established about a century ago by the famous British physiologists Charles G. Douglas and John S. Haldane from Oxford University. Their results were published in 1909 in the article The regulation of normal breathing by the Journal of Physiology (Douglas & Haldane, 1909).
Normal breathing is regular, invisible (no chest or belly movements), and inaudible (no panting, no wheezing, no sighing, no yawning, no sneezing, no coughing, no deep inhalations or exhalations).
In order to define one’s breathing pattern, measure your body oxygenation or breath holding time after your usual exhalation, but only until the first stress or discomfort.
The person with normal breathing is going to have about 40 s breath holding time (or body oxygenation index). In case of chronic over-breathing, breath holding time becomes shorter indicating reduced body oxygen stores.
Sick people have deep and fast breathing 24/7 and reduced body oxygenation (usually about 10-20 s of oxygen in tissues). In the severely sick and critically ill patients, body oxygenation is below 10 s.
Dr. Buteyko, based on his studies of thousands of healthy and sick people,
suggested different norms for breathing (e.g., Buteyko, 1991):
- normal minute ventilation: 4 l/min;
- normal tidal volume (air volume breathed in during a single breath): 500 ml;
- normal breathing frequency: 8 breaths per minute;
- normal inspiration: about 1.5 seconds;
- normal exhalation: 2 seconds;
- normal automatic pause (or period of no breathing or total relaxation after exhalation): 4
seconds;
- normal breath holding time (after usual exhalation and without stress at the
end of the test): 60 seconds;
- normal CO2 concentrations in the alveoli and arterial blood – 6.5% or about 46
mm Hg.
Buteyko KP, Method of voluntary elimination of deep breathing, Buteyko method [in Russian], in Buteyko method. Its application in medical practice, ed. by K.P. Buteyko, 2-nd ed., 1991, Titul, Odessa, p.148-165.
Douglas CG, Haldane JS, The regulation of normal breathing, Journal of Physiology 1909; 38: p. 420–440.
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).