Normal Breathing Pattern (Normal Respiration)

Clouds and forest Modern physiology 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 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 Chart

Normal Breathing (Respiration) Pattern Chart in Time

This chart shows 4 breathing cycles of the normal respiration pattern for normal subjects:

inhalation (the upward lines), exhalation (the downward lines) and automatic pause

(the almost horizontal lines) accompanied by relaxation of all breathing muscles.

Features of the normal breathing pattern

Woman meditating Apart from numbers, there are many important qualities of normal respiration. If you have healthy friends or relatives, you can easily observe that 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 accompanied by relaxation of all breathing muscles. These parameters of normal breathing 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). You can find these 1920-1930's studies in the Hyperventilation: Present in Over 90% of Normal People with 24 medical publications. Some old medical textbooks suggested 4 L/min as normal for healthy people.

Note that minute ventilation of modern healthy people is still nearly normal (about 6-7 L of air in one minute) as this Table Normal Minute Ventilation (14 Studies) in Healthy Subjects indicates.

Reference Web Pages: Breathing norms, Medical Graphs and Tables about Breathing Rates (Minute Ventilation) and Body Oxygen in Healthy, Normal and Sick People
Breathing norms Parameters, graph, and description of the normal breathing pattern
6 breathing myths 6 myths about breathing and body oxygenation (prevalence: over 90%)
Hyperventilation Definitions of hyperventilation: their advantages and weak points
Hyperventilation Syndrome in the Sick. Table 1. Western scientific evidence about prevalence of CHV (chronic hyperventilation) in patients with various chronic conditions (34 medical studies)
Normal Minute Ventilation in Healthy Subjects: Easy and Light Breathing (14 Studies)
Hyperventilation Prevalence Present in Over 90% of Normal People (24 medical publications)
HV and hypoxia How and why deep breathing reduces oxygenation of cells and tissues of all vital organs
Body oxygen test How to measure your own breathing and body oxygenation (a simple DIY test)
Body oxygen in healthy Table 4. CP (body oxygen level) in healthy people (27 medical studies)
Body oxygen in sick Table 5. CP (body oxygen level) in sick people (14 medical studies)
Buteyko Table of Health Zones with clinical description of most common zones
Morning HV Morning hyperventilation effect or how and why critically ill people are most likely to die during early morning hours

References: CO2 Effects Web Pages
Vasodilation: CO2 expands arteries and arterioles facilitating perfusion (or blood supply) to all vital organs
The Bohr effect How and why oxygen is released by red blood cells in tissues
Cell Oxygen Levels and oxygen transport are controlled by alveolar CO2 and breathing
Oxygen Transport depends on breathing and these two effects (Vasoconstriction-Vasodilation and the Bohr effect) are parts of two diagrams that summarize influences of hypocapnia (low CO2 content in the blood and cells) on circulation and O2 delivery
Free Radical Generation takes place due to anaerobic cell respiration caused by cell hypoxia. Hence, antioxidant defenses of the human body are also regulated by CO2 and breathing
Inflammatory Response is controlled by breathing since hypoxia leads to or intensifies chronic inflammation through over-expression of the hypoxia-inducible factor 1, while normal breathing reduces these processes
Nerve stabilization takes place due to calmative or sedative effects of carbon dioxide in neurons or nerve cells
Muscle relaxation or relaxation of muscle cells is normal at high CO2, while hypocapnia causes muscular tension, poor posture and, sometimes, aggression and violence
Brochodilation - dilation of airways (bronchi and bronchioles) by carbon dioxide, and their constriction due to hypocapnia
CO2: Best Natural Cough Suppressant and "home remedy" since it calms urge-to-cough nerve receptors located in the tracheobronchial tree and larynx
Blood pH regulation and regulation of other bodily fluids
CO2: Lung Damage Healer: Elevated carbon dioxide prevents injury and promotes healing of lung tissues
CO2: Skin and Tissue Healer
Synthesis of Glutamine in the Brain, CO2 fixation, and other chemical reactions
CO2 myth "CO2 is a toxic waste gas" myth
Breathing control How is our breathing regulated? Why hypocapnia makes breathing uneven and erratic?

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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