Best Cough Suppressants: CO2 and NO

Woman coughing In order to find the best cough suppressors, we need to find the cause of coughing. Coughing results in very large minute ventilation rates. While normal breathing at rest requires only 6 liters of air per minute (healthy subjects), coughing increases ventilation at least up to 3-4 times. As a result, people breathe up to 15-20 liters per minute or more. Later, after bouts of coughing are subsided, the person continues to breathe much more than the medical norm (chronic hyperventilation) due to reset of the respiratory center to lower CO2.

Low CO2 levels in the airways (alveolar hypocapnia) irritate urge-to-cough nerve receptors located in the tracheobronchial tree and larynx (see the links below) causing chronic problems with coughing.

It is known that coughing in very common in people with, for example, asthma, bronchitis, COPD, and cystic fibrosis. Do they have heavy breathing at rest?

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

What are the effects of hyperventilation? It leads to low CO2 levels in the lungs that reduces oxygen levels in body cells. Tissue hypoxia increases inflammation, and suppresses the immune system (see the links below). Thus, hypocapnia (reduction in carbon dioxide levels in the lungs) is a suppressant of the immune system.

Effects of over breathing on brain oxygen levels Note that some people can experience arterial hypercapnia (increased CO2) due to low CO2 in the lungs since carbon dioxide has a profound positive effect on lung tissue. It dilates bronchi and bronchioles immediately improving the ventilation-perfusion ratio.

Those who have normal lungs suffer from arterial hypocapnia (low CO2 in the blood), and that reduces blood and oxygen supply to all vital organs (see the picture on the right).

CO2: natural cough suppressant

Carbon dioxide is the best natural cough suppressant since it is the most needed chemical to reduce inflammation, improve immunity and increase body oxygen levels. Furthermore, medical research suggests that alveolar hypocapnia (low CO2 in airways) is the key cause of chronic cough (see quotes from medical studies below).

Carbon dioxide molecule image Reduced levels of CO2 overexcite all nerve cells in the nervous system causing their irritability (see medical references below). Urge-to-cough nerve receptors are also irritated due to low CO2 and, if conditions are suitable (inflammation or airways, breathing cold air through the mouth, respiratory infections, allergy triggers, extra mucus, and so forth) this leads to ... chronic coughing. This is because urge-to-cough nerve receptors are located in the tracheobronchial tree and larynx and are highly sensitive to slight changes in CO2 (as small as 1-2 mm Hg).

In addition, hyperventilation and coughing through the mouth mechanically irritates airways, overcools and dries them, and reduces oxygenation of brain and body cells. All these effects worsen coughing attacks and destroy heath.

Therefore, CO2 is natural cough suppressant that directly pacifies urge-to-cough receptors. Apart from this nerve-calming effect, higher CO2 levels in airways increase oxygen levels in body cells, improve immunity, prevent chronic inflammation, dilate blood vessels, and cause many other natural and beneficial effects (see links to medical studies below).

Nitric oxide: another potent natural cough suppressant

Doctor with a hushing sign Nitric oxide is produced in various parts of the body, and the sinuses are one of the primary sites. Nasal nitric oxide is crucial to fight pathogens in the lungs due to its powerful effects on bacteria, viruses and fungi. It is also a potent natural vasodilator. (Nitroglycerine, a popular drug for heart attacks, works due to its conversion into nitric oxide.) Nitric oxide is synthesized from arginine (amino acid) that humans get with food. Mouth breathing (e.g., during sleep) and coughing through the mouth blow away nasal nitric oxide causing more severe problems with coughing.

Best home remedies to stop coughing

Furthermore, if you suffer from coughing, you can practically prove that CO2 is the best cough suppressant. There are easy breathing exercises used by about 200 Soviet and Russian medical doctors. These exercises can suppress or stop coughing faster than cough suppressing medications: Persistent Cough Home Remedies: 3 Easy, Proven Breathing Exercises and How to Stop Cough at Night (another natural home solution).

Here is a video clip from YouTube: Cough Medicine, Syrups, and Best Cough Suppressants: CO2 and NO.

References (CO2: natural or body-made sedative and tranquilizer of nerve cells)

Balestrino M, Somjen GG, Concentration of carbon dioxide, interstitial pH and synaptic transmission in hippocampal formation of the rat, J Physiol 1988, 396: p. 247-266. - “... The brain, by regulating breathing, controls its own excitability...”

Brown EB, Physiological effects of hyperventilation, Physiol Reviews 1953 Oct, 33 (4): p. 445-471. - “Studies designed to determine the effects produced by hyperventilation on nerve and muscle have been consistent in their finding on increased irritability”

Davis H, Pascual W, Rice LH (1928), Quantitative studies of the nerve impulse. Amer. J. Physiol. 86, 706-724.

Huttunen J, Tolvanen H, Heinonen E, Voipio J, Wikstrom H, Ilmoniemi RJ, Hari R, Kaila K, Effects of voluntary hyperventilation on cortical sensory responses. Electroencephalographic and magnetoencephalographic studies, Exp Brain Res 1999, 125(3): p. 248-254. - Hyperventilation ... "leads to spontaneous and asynchronous firing of cortical neurons".

Krnjevic K, Randic M and Siesjo B, Cortical CO₂ tension and neuronal excitability, J of Physiol 1965, 176: p. 105-122. - In section "Changes in membrane resting potentials": "Hypercapnia was associated with an increase in resting potential and the period of falling Pco2, with depolarization..." "Cortical cells are remarkably sensitive to variations in PCo2; even changes of the order of 1-2 mm Hg may be sufficient to produce a clear alteration in their excitability. On the whole, the main effect of hypercapnia is depressant...." "There is general agreement that an increase in Pco2, tends to reduce the excitability of vertebrate nerve fibres (Davis, Pascual & Rice, 1928; Necheles & Gerard, 1930; Lorente de No, 1947) probably by raising the membrane potential (Lorente de No, 1947; Shanes, 1948)."

Lorente DE (1947), A study of nerve physiology. Stud. Rockefeller Inst. med. Res. 131, pp. 148-193.

Necheles H & Gererd RW (1930), The effect of carbon dioxide on nerve, Amer. J. Physiol. 93, 318-336.\

Shanes AM (1948), Metabolic changes of the resting potential in relation to the action of carbon dioxide, Amer. J. Physiol. 153, 93-108.

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?

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

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