Bronchoconstriction: The Real Story about Bronchoconstriction
(definition) is defined as the narrowing of the airways in the lungs (bronchi and
bronchioles). Air flow in air passages can get restricted due to 3 factors:
- a spasmodic state of the smooth muscles in bronchi and bronchioles
- an inflammation of the airways
- excessive production of mucus due to an allergic reaction or irritation caused by mechanical friction of air (due to shear stress), overcooling or drying of airways.
Bronchoconstriction is common in people with respiratory problems, such as asthma, COPD, and cystic fibrosis. Medical sources continue to misinform public about the true causes of bronchoconstriction. Here are the facts.
Ventilation rates (chronic diseases)
| All references or
click below for abstracts
|Normal breathing||6 L/min||-||Medical textbooks|
|Healthy Subjects||6-7 L/min||>400||Results of 14 studies|
|Asthma||13 (~+mn~2) L/min||16||Chalupa et al, 2004|
|Asthma||15 L/min||8||Johnson et al, 1995|
|Asthma||14 (~+mn~6) L/min||39||Bowler et al, 1998|
|Asthma||13 (~+mn~4) L/min||17||Kassabian et al, 1982|
|Asthma||12 L/min||101||McFadden, Lyons, 1968|
|COPD||14 (~+mn~2) L/min||12||Palange et al, 2001|
|COPD||12 (~+mn~2) L/min||10||Sinderby et al, 2001|
|COPD||14 L/min||3||Stulbarg et al, 2001|
|Cystic fibrosis||15 L/min||15||Fauroux et al, 2006|
|Cystic fibrosis||10 L/min||11||Browning et al, 1990|
|Cystic fibrosis*||10 L/min||10||Ward et al, 1999|
|CF and diabetes*||10 L/min||7||Ward et al, 1999|
|Cystic fibrosis||16 L/min||7||Dodd et al, 2006|
|Cystic fibrosis||18 L/min||9||McKone et al, 2005|
|Cystic fibrosis*||13 (~+mn~2) L/min||10||Bell et al, 1996|
|Cystic fibrosis||11-14 L/min||6||Tepper et al, 1983|
As a result of heavy breathing, all these people suffer from alveolar hypocapnia (lack of CO2 in airways).
Cause of bronchoconstriction
It is a known physiological law that all smooth muscles are highly sensitive to CO2 levels. Thus, spasm in the smooth muscles of bronchi and bronchioles is a normal physiological reaction to alveolar hyperventilation (Badier et al, 1998; Clarke et al, 1982; Jamison et al, 1987; O'Cain et al, 1979; Sterling, 1968).
While there are many chemicals that can cause either bronchoconstriction or bronchodilation, CO2 plays the key role due to two factors: its high bronchodilatory potency and additional negative systemic effects caused by alveolar hypocapnia (lack of CO2). What are those?
Chronic hyperventilation (breathing more air than the medical norm) also leads to cell hypoxia, generation of reactive oxygen species (free radicals), and immunosuppression. (This can happen with or without ventilation-perfusion mismatch: blood CO2 levels can be below the norm or too high.)
As a result, overbreathing produces additional effects that worsen conductivity of airways, such as immunosuppression, frequent respiratory infections, excessive production of sputum (mucus) and airway inflammation (see links to studies below).
Furthermore, overbreathing also leads to increased losses of water from the mucosal layers of airways and overcooling of airways due to increased heat losses. These effects also favor frequent respiratory infections.
Symptoms of bronchoconstriction
These effects cause further airway obstruction, difficulty breathing, wheezing, coughing, and dyspnea (shortness of breath) amplifying the effects of bronchospasm.
Causes and mechanism of bronchoconstriction
Consider medical evidence related to breathing parameters at rest in people with bronchoconstriction (see the Table above). We see that these patients breathe at rest (in stable conditions) much more air than the medical norm. Over breathing leads to low CO2 in the airways and causes other effects summarized here.
Bronchospasm can also happen due to an allergic reaction caused by the release of histamine. This allergic reaction leads to edema and inflammation of airways, as often happens in people with asthma, bronchitis, emphysema, and other COPD-related conditions. However, chronic hyperventilation causes immune dysfunction, and, therefore, it also promotes the appearance of allergies.
Since cell hypoxia promotes chronic inflammation, people with these health conditions (asthma, bronchitis, and so on), as well as people with cystic fibrosis, tuberculosis, sarcoidosis, bronchiectasis, bronchiolitis, and many other lung diseases, experience chronic spasm in the smooth muscles of airways or bronchospasm, combined with other negative effects caused by hypocapnia.
This YouTube video explains the cause of bronchoconstriction.
Note about coughing. Coughing through the mouth multiplies all these negative effects of hyperventilation several fold. There are effective breathing techniques how to suppress coughing.
Treatment of bronchoconstriction
Over 170 Russian medical doctors found an effective way to deal with bronchoconstriction. This medical therapy is based on restoration of normal alveolar CO2 levels. The Buteyko method is approved by the Russian Ministry of Health and has been applied on more than 200,000 people with health problems that involve bronchoconstriction (such as asthma, bronchitis, COPD, cystic fibrosis and many others). According to these Russian doctors, patients need to slow down their heavy breathing and achieve more than 20 s for the body-oxygen test to prevent symptoms of bronchospasm at rest. Nose breathing during exercise often reduces or prevents exercise-induced asthma.
Breathing exercises with breathing devices (such as the Frolov breathing device, DIY breathing device, and Samozdrav) are very effective ways to increase body oxygen levels. Oxygen Remedy online breathing classes is probably the easiest way to learn and the most effective therapy for bronchoconstriction. Lifestyle changes are also necessary to prevent overbreathing due to sleep (supine sleep and mouth breathing), meals (overeating), exercise, and other factors.
Badier M, Beaumont D, Orehek J, Attenuation of hyperventilation-induced
bronchospasm by terfenadine: a new antihistamine, J Allergy Clin Immunol.
Clarke PS, Jarrett RG, Hall GJ, The protective effect of ipratropium bromide aerosol against bronchospasm induced by hyperventilation and the inhalation of allergen, methacholine and histamine, Ann Allergy. 1982 Mar;48(3):180-3.
Jamison JP, Glover PJ, Wallace WF, Comparison of the effects of inhaled
ipratropium bromide and salbutamol on the bronchoconstrictor response to
hypocapnic hyperventilation in normal subjects, Thorax. 1987 Oct; 42(10):
....This suggests that bronchoconstriction in response to hypocapnic hyperventilation in normal subjects is not mediated via a cholinergic reflex.
O'Cain CF, Hensley MJ, McFadden ER Jr, Ingram RH Jr, Pattern and mechanism of airway response to hypocapnia in normal subjects, J Appl Physiol. 1979 Jul;47(1):8-12.
We examined the bronchoconstriction produced by airway hypocapnia in normal subjects... Pretreatment with a beta-sympathomimetic agent blocked the response, whereas atropine pretreatment did not, suggesting that hypocapnia affects airway smooth muscle directly, not via cholinergic efferents.
Reynolds AM, McEvoy RD, Tachykinins mediate hypocapnia-induced
bronchoconstriction in guinea pigs, J Appl Physiol. 1989
... We conclude that, in the guinea pig lung, HIBC [hypocapnia-induced bronchoconstriction] is mediated by TKs [tachykinins] that are released after the activation of bronchial axonal reflexes.
Sterling GM, The mechanism of bronchoconstriction due to hypocapnia in man, Clinical Science 1968 Apr; 34(2): p. 277-285.
Straub NC, Section V, The Respiratory System, in Physiology, edited by. Berne RM & Levy MN, 4th edition, Mosby, St. Louis, 1998.
* Upper illustration by Victor Lunn-Rockliffe
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