Normal Breathing Pattern (Normal Respiration Cycle)
textbooks suggest the following parameters of the
normal breathing pattern (normal respiration) at rest for healthy subjects:
- inhalation is 1.5-2 s
- exhalation is 1.5-2 s
- automatic pause of almost no breathing is 2 s
- tidal volume (the depth of inhalation) is 500-600 ml
- breathing frequency (or Rf - respiratory frequency or respiratory rate) is 10-12 breaths/min.
The international physiological norm for the breathing rate at rest is 6 L/min (for a 70-kg man). Normal stress-free breath holding time after usual exhalation (that correlates with body-oxygen content) is 40 s. References for medical textbooks that provide these values are below.
Normal respiration cycle chart
This chart shows 4 breathing cycles of the normal
respiration pattern for normal subjects:
(the upward lines), exhalation (the downward lines) and
(the almost horizontal lines)
accompanied by relaxation of all breathing muscles.
Features of the normal breathing pattern
Apart from numbers, there are many important qualities of normal respiratory pattern. Their breathing is slow, regular, nasal only, diaphragmatic, invisible 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 normal body oxygen level is about 40 s for the medical norm and 60 s for the Buteyko norm.
Most of the job of inhalation (up to 80-90%) is done by the diaphragm, the main breathing muscle. Exhalation is passive and is accompanied by the relaxation of all breathing muscles. These parameters of the normal respiration cycle were established about 100 years ago. Published medical articles found that in the 1920-1930's, normal subjects were breathing even less air at rest than the medical norm (6 L of air per minute).
Most modern people breathe more than the norm
Do you know that over 90% of modern "normal subjects" breathe at rest much more air than the medical norms? One page of this site has a historical chart based on 24 medical publications. It shows changes in respiratory patterns during nearly 100 years. The link to this page is provided right below here as your bonus content.
Medical textbooks references
Ganong W, Review of medical physiology; 15-th ed., 1995, Prentice Hall Int., London.
Guyton A, Physiology of the human body; 6-th ed., 1984, Suanders College Publ., Philadelphia.
McArdle W, Katch F, Katch V, Essentials of exercise physiology (Second edition); Lippincott, Williams and Wilkins, London 2000.
Straub N, Section V, The Respiratory System, in Physiology, editors. R Berne & M Levy, 4-th edition, Mosby, St. Louis, 1998.
Summary of values useful in pulmonary physiology: man. In the Section: Respiration and Circulation, ed. by P Altman & D Dittmer, 1971, Bethesda, Maryland (Federation of American Societies for Experimental Biology).
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