Exercise-Induced Asthma: Definition, Causes and Treatment

Man with exercise induced asthma

Exercise-Induced Asthma: Definition

Exercise-induced asthma is defined as a type of asthma attack that is triggered by physical activity. During such asthma exacerbation, airways are constricted, and there is limited flow of air to the lungs with all 3 classical signs of asthma: bronchoconstriciton, inflammation of airways, and excessive production of mucus. As a result of these factors, gas exchange between outer air and the alveoli in the lungs is limited. The person feels air hunger (of self-suffocation) and is often in a state of panic or anxiety during or immediately after running, swimming, cycling, and other forms of physical exercise.

Causes and mechanism of exercise induced asthma

Causes of exercise-induced asthma

There are 4 significant changes in the respiratory system that take place due to exercise in comparison with quiet breathing at rest. These changes are shown on the chart.

Note that normal breathing at rest is very small and slow: only 6 L/min per min at rest with 10-12 breaths per min for the respiratory frequency. During physical exercise, most normal people can breathe more than 100 L/min. This causes increased mechanical stress (shear stress) on airways due to movements of large volumes of air.

However, the key triggering factors of exercise-induced asthma relate to losses in alveolar CO2 (CO2 content in the airways). Since CO2 is a powerful relaxant of smooth muscles, mouth breathing during exercise leads to alveolar hypocapnia (CO2 deficiency) causing bronchoconstriction (see the links below for medical research in this area). Indeed, those medical studies that compared effects of mouth and nose breathing found that nose breathing during exercise provides definite benefits for people with asthma during exercise with less or no bronchospasm involved (Shturman-Ellstein, 1978; Mangla & Menon, 1981).

Man runing on a beach Nose breathing produces the following effects on the respiratory system during exercise:
- higher levels of CO2 in the airways causing bronchodilation and reduced heart rate
- warming of air in the sinuses and prevention of overcooling of airways
- humidification of the incoming air flow in the sinuses and prevention of drying of airways
- greatly reduced friction in airways due to hypercapnic bronchodilation and reduced minute ventilation
- increased levels of nasal nitric oxide absorbed in the lungs and blood
- greater increase in body oxygen levels after exercise (this can be checked next morning using the body oxygen test)
- greater training effect (larger increase in VO2max), faster adaptation to higher intensity of training, and faster recovery from injuries.

The only disadvantage of nose breathing is that relatively unfit people are usually not able to exercise rigorously due to their low body oxygen content at rest caused by heavy or deep breathing. This relates to many asthmatics. Let us consider how. While normal breathing at rest is only 6 L/min for a 70-kg man, asthmatics breathe about 12-15 L/min.

Chronic hyperventilation explains expected effects of asthma (low body oxygen levels 24/7, the hypersensitive immune system, bronchospasm, and chronic inflammation of airways).

Medical doctors smiling According to the clinical experience of more than 180 Russian medical doctors teaching the Buteyko breathing technique, physical exercise with nose breathing is the most natural and most effective method to increase body oxygenation and eliminate hyperventilation naturally for those people who have less than 10 seconds for the body oxygen test. However, these MDs also found that most sick people should start with low intensity exercise (e.g., walking or fast walking) with nose breathing only. These patients need to increase their body oxygen levels up to 20 seconds or more in order to exercise rigorously with nose breathing only. In most cases, this may take up to 2-3 weeks.

Therefore, nose breathing during exercise is an excellent method and therapy to eliminate asthma, reduce medication, prevent exercise induced asthma, achieve greater improvements in sports performance, and increase body oxygen levels.

Warning. In conditions of cold weather, even nasal breathing does not prevent penetration of cold air into bronchi and bronchioles. This creates mild inflammation and worsens symptoms of asthma. This problems can be solved by reduced intensity of exercise (with reduced ventilation during exercise) and using a scarf, dust musk or other solutions that will provide warmer air for inhalations. Therefore, each asthmatic needs to find their personal level of intensity and thermo protection to prevent any additional inflammation. due to exercise.

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
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

Shturman-Ellstein R, Zeballos RJ, Buckley JM, Souhrada JF, The beneficial effect of nasal breathing on exercise-induced bronchoconstriction, American Review of Respiratory Diseases 1978 Jul; 118(1): 65-73.
In the first step of a study of the relation of nasal and oral breathing during moderate treadmill exercise to the onset of bronchoconstriction in young patients with perennial bronchial asthma, it was observed that most subjects spontaneously breathed with their mouths open when instructed to breathe "naturally." Subsequently, when they were required to breathe only through the nose during the exercise, an almost complete inhibition of the postexercise bronchoconstrictive airway response was demonstrated. When instructed to breathe only through the mouth during exercise, an increased bronchoconstrictive airway response occurred, as measured by spirometry, flow-volume relationships, and body plethysmography...

Mangla PK, Menon MP, Effect of nasal and oral breathing on exercise-induced asthma, Clinical Allergy. 1981 Sep; 11(5): 433-9.
The effect of nasal as well as oral breathing during level-ground running for 6 min on the post exercise bronchial response was studied in fifteen people (five asthmatics with exercise liability, five asthmatics with no such liability and five normals). Each patient did the exercise twice; once with the nose clipped and once with the mouth closed. FEV1 was measured before exercise, immediately after exercise and at 5, 10, 15, 20 and 30 min thereafter. A fall in FEV1 of 20% or more from the basal level was taken as evidence of bronchoconstriction. When the patients were required to breath only through the nose during the exercise, the post-exercise bronchoconstrictive response was markedly reduced as compared with the response obtained by oral breathing during exercise, indicating a beneficial effect of nasal breathing. Nasal breathing was beneficial as compared with oral breathing in normals as well...

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