Dyspnea on Exertion (Exertional Dyspnea): Causes and Treatment

What causes exertional dyspnea and its pathophysiology

Man with dyspnea and chest pain Dyspnea on exertion is caused by various factors. However, low body oxygenation is the key parameter that is always present in people with this symptom. Mouth breathing and chest breathing are among the main additional causes of exertional dyspnea since they reduce body and brain oxygenation and create the sensation of air hunger (shortage of air). People with heart disease, cancer, diabetes, asthma, cystic fibrosis, COPD and many other chronic conditions are most likely to experience this debilitating symptom, as many studies found.

What do we know about their body oxygenation and breathing at rest? Why do people with chronic diseases, but not healthy people, experience exertional dyspnea? What are the main problems with oxygen transport in the sick? Consider these evidence.

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
Heart disease	15 (±4) L/min	22	Dimopoulou et al, 2001
Heart disease	16 (±2) L/min	11	Johnson et al, 2000
Heart disease	12 (±3) L/min	132	Fanfulla et al, 1998
Heart disease	15 (±4) L/min	55	Clark et al, 1997
Heart disease	13 (±4) L/min	15	Banning et al, 1995
Heart disease	15 (±4) L/min	88	Clark et al, 1995
Heart disease	14 (±2) L/min	30	Buller et al, 1990
Heart disease	16 (±6) L/min	20	Elborn et al, 1990
Pulm hypertension	12 (±2) L/min	11	D'Alonzo et al, 1987
Cancer	12 (±2) L/min	40	Travers et al, 2008
Diabetes	12-17 L/min	26	Bottini et al, 2003
Diabetes	15 (±2) L/min	45	Tantucci et al, 2001
Diabetes	12 (±2) L/min	8	Mancini et al, 1999
Diabetes	10-20 L/min	28	Tantucci et al, 1997
Diabetes	13 (±2) L/min	20	Tantucci et al, 1996
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
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
Sleep apnea	15 (±3) L/min	20	Radwan et al, 2001
Liver cirrhosis	11-18 L/min	24	Epstein et al, 1998
Hyperthyroidism	15 (±1) L/min	42	Kahaly, 1998
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
Epilepsy	13 L/min	12	Esquivel et al, 1991
CHV	13 (±2) L/min	134	Han et al, 1997
Panic disorder	12 (±5) L/min	12	Pain et al, 1991
Bipolar disorder	11 (±2) L/min	16	MacKinnon et al, 2007
Dystrophia myotonica	16 (±4) L/min	12	Clague et al, 1994

Medical people Chronic hyperventilation (or automatic deep breathing pattern) leads to alveolar hypocapnia (lack of CO2) that causes low oxygen levels in body cells. Therefore, these people should have more problems during physical exertion since any forms of exercise require additional oxygen causing dyspnea on exertion.

Healthy or normal breathing is very small and slow. It is imperceptible or unperceivable (only about 500 ml for tidal volume, and 10-12 breaths/min with 6 L/min for minute ventilation at rest for a 70-kg person). Patients with dyspnea commonly have over 12 L/min (double the norm) for their ventilation rates at rest and over 18 breaths/min for respiratory frequency.

Overbreathing leads to greatly increased work of breathing due to large minute ventilation rates and causes many other adverse effects, apart from exertional dyspnea.

Causes of exertional dyspnea (breathlessness)

Exacerbating causes in the pathophysiology of exertional dyspnea are:
- oral breathing (due to reduction in NO or nitric oxide absorption and alveolar CO2)
- thoracic breathing (due to reduction in the arterial oxygenation causing hypoxemia)
- presence of chronic inflammation and sputum in airways causing further narrowing or obstruction of air movement.

Older man with dyspnea on exertion (breathlessness) due to exercise Physical exertion, due to anaerobic cell respiration at rest and elevated resting blood lactate, worsens gas exchange and causes further overbreathing and additional losses in alveolar CO2. This leads to acute exertional dyspnea. Acute dyspnea leads to even heavier and faster breathing due to a negative feedback in breathing control caused by a prominent O2 drive (hunger for air), instead of normal CO2-based control of respiration. Respiratory receptors located in the brain sense low brain oxygenation creating the sensation of air hunger and trying to increase ventilation.

Treatment of dyspnea on exertion

Significant reduction in exertional dyspnea has been found in numerous clinical trials after the application of various breathing techniques and respiratory devices that gradually change automatic (basal) breathing patterns at rest, reduce the degree of hyperventilation, and increase body oxygen levels. Generally, patients with exertional dyspnea need to achieve more than 20 s for the body oxygen test to prevent dyspnea at rest and on exertion.

Ripamonti C. Management of dyspnea in advanced cancer patients. Support Care Cancer. 1999; 7: p. 233-243.
"Dyspnea has been defined as an “uncomfortable awareness of breathing"

Coyne PJ, Viswanathan R, Smith TJ, Nebulized fentanyl citrate improves patients' perception of breathing, respiratory rate, and oxygen saturation in dyspnea, J Pain Symptom Manage 2002; 23: p. 157–160.
“Dyspnea is exceedingly common. Ruben and Mor found that 70% of 1500 cancer patients suffered dyspnea during their last four weeks of life.”

Reuben DB, Mor V, How much of a problem is dyspnoea in advanced cancer? Palliat Med 1991; 5: 20–26.
“Introduction. Although a number of articles on dyspnoea in terminal cancer have appeared, [1-8] in terms of publications, this symptom remains a poor relation when compared with pain. Anyone, however, who has looked after dying people will be aware that dyspnoea is a common and often distressing symptom, particularly if severe. In such cases patients may feel that they may die from lack of air - even pain does not have this connotation. This is demonstrated in Comroe’s definition of dyspnoea as ’difficult, laboured, uncomfortable breathing; it is an unpleasant type of breathing, though it is not painful in the usual sense of the word. It is subjective, and, like pain, it involves both perception of the sensation by the patient and his reaction to the sensation.”

Dudgeon DJ, Managing dyspnea and cough, Hematol Oncol Clin North Am 2002 Jun; 16(3): p.557-577.
"Dyspnea, like pain, is a subjective experience that incorporates physical elements and affective components. Management of breathlessness in patients with cancer requires expertise that includes an understanding and assessment of the multidimensional components of the symptom, knowledge of the pathophysiologic mechanisms and clinical syndromes that are common in cancer, and familiarity with the indications and limitations of the available therapeutic approaches. Relief of breathlessness should be the goal of treatment at all stages of cancer. Good control of dyspnea will improve the patient's quality of life."

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

Go to Hyperventilation Symptoms

HTML Comment Box is loading comments...