Bronchoconstriction: The Real Story about Bronchoconstriction

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.

Minute ventilation rates (chronic diseases)

Condition	Minute ventilation	Number of people	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
COPD	14 (±2) l/min	12	Palange et al, 2001
COPD	12 (±2) l/min	10	Sinderby et al, 2001
COPD	14 l/min	3	Stulbarg et al, 2001
Asthma	13 (±2) l/min	16	Chalupa et al, 2004
Asthma	15 l/min	8	Johnson et al, 1995
Asthma	14 (±6) l/min	39	Bowler et al, 1998
Asthma	13 (±4) l/min	17	Kassabian et al, 1982
Asthma	12 l/min	101	McFadden & Lyons, 1968
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 (±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.

Reference pages: Breathing norms and medical facts:
- Breathing norms: Parameters, graph, and description of the normal breathing pattern
- 6 breathing myths: Myths and superstitions about breathing and body oxygenation (prevalence: over 90%)
- Hyperventilation: Definitions of hyperventilation: their advantages and weak points
- Hyperventilation syndrome: Western scientific evidence about prevalence of chronic hyperventilation in patients with chronic conditions (37 medical studies)
- Normal minute ventilation: Small and slow breathing at rest is enjoyed by healthy subjects (14 studies)
- Hyperventilation prevalence: Present in over 90% of normal people (24 medical studies)
- HV and hypoxia: How and why deep breathing reduces oxygenation of cells and tissues of all vital organs
- Body-oxygen test (CP test) : How to measure your own breathing and body oxygenation (two in one) using a simple DIY test
- Body oxygen in healthy: Results for the body-oxygen test for healthy people (27 medical studies)
- Body oxygen in sick : Results for the body-oxygen test for sick people (14 medical studies)
- Buteyko Table of Health Zones: Clinical description and ranges for breathing zones: from the critically ill (severely sick) up to super healthy people with maximum possible body oxygenation
- Morning hyperventilation: Why people feel worse and critically ill people are most likely to die during early morning hours

References: pages about CO2 effect:
- 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: How alveolar CO2 influences oxygen transport
- Oxygen transport: O2 transport is controlled by vasoconstriction-vasodilation and the Bohr effects, both of which rely on CO2
- Free radical generation: Reactive oxygen species are produced within cells due to anaerobic cell respiration caused by cell hypoxia
- Inflammatory response: Chronic inflammation in fueled by the hypoxia-inducible factor 1, while normal breathing reduces and eliminates inflammation
- Nerve stabilization: People remain calm due to calmative or sedative effects of carbon dioxide in neurons or nerve cells
- Muscle relaxation: Relaxation of muscle cells is normal at high CO2, while hypocapnia causes muscular tension, poor posture and, sometimes, aggression and violence
- Bronchodilation: Dilation of airways (bronchi and bronchioles) is caused by carbon dioxide, and their constriction by hypocapnia (low CO2)
- Blood pH: Regulation of blood pH due to breathing and regulation of other bodily fluids
- CO2: lung damage: Elevated carbon dioxide prevents lung injury and promotes healing of lung tissues
- CO2: Topical carbon dioxide can heal skin and tissues
- Synthesis of glutamine in the brain, CO2 fixation, and other chemical reactions
- Deep breathing myth: Ignorant and naive people promote the idea that deep breathing and breathing more air at rest is beneficial for health
- Breathing control: How is our breathing regulated? Why hypocapnia makes breathing uneven, irregular and erratic.

References

Badier M, Beaumont D, Orehek J, Attenuation of hyperventilation-induced bronchospasm by terfenadine: a new antihistamine, J Allergy Clin Immunol. 1988 Feb;81(2):437-40.

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): 809-14.
....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 Dec;67(6):2454-60.
... 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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