Introduction
Breathlessness, also called shortness of breath, is a common symptom of various disorders. It is also referred to as dyspnea. Breathlessness on exertion is also known as dyspnea on exertion or exertional dyspnea. It is a normal symptom of physical exertion, but it can be pathological. It can be the manifestation of respiratory, cardiac, neuromuscular, psychogenic, or systemic illness or a combination of these conditions.
What Is Breathlessness on Exertion?
Breathlessness on exertion is the sensation of breathing difficulty experienced during physical activities. It is experienced during exercises, and it improves with rest. Physical exertion refers to the exercises that increase the oxygen demand above the body’s ability to compensate. Breathlessness is experienced when the boy lacks oxygen delivery. Exertional dyspnea can be due to interactions with receptors in the central nervous system, and peripheral chemoreceptors, and mechanoreceptors present in the chest wall and the respiratory tract.
What Are the Causes of Breathlessness on Exertion?
Breathlessness on exertion is not a disease but a symptom of various diseases. It is usually caused by respiratory system and cardiac system disorders. It can also be caused by other systemic illnesses or a combination of these conditions.
Respiratory causes for breathlessness on exertion include asthma, acute exacerbation of chronic obstructive pulmonary disorder (COPD), asthma, pneumonia, pulmonary embolism, lung cancer, interstitial lung disease, aspiration, or pneumothorax.
Cardiovascular causes of exertional dyspnea include congestive heart failure, pulmonary edema, acute coronary syndrome, pericardial tamponade, pulmonary hypertension, cardiac arrhythmia, cardiac ischemia, intracardiac shunting, and a valvular heart defect. Of all the cardiac disorders, congestive heart failure is the major cause of dyspnea on exertion.
Other systemic illnesses that cause breathlessness on exertion are anemia, acute renal failure, metabolic acidosis, epiglottitis, angioedema, sepsis, anaphylaxis, liver cirrhosis, and thyrotoxicosis.
Neurological conditions like spinal cord injury, phrenic nerve injury, Guillain-Barre syndrome, muscular dystrophy, multiple sclerosis, and amyotrophic lateral sclerosis can also cause exertional dyspnea. Inflammatory disease like sarcoidosis also presents with shortness of breath.
What Are the Effects of Breathlessness on Exertion?
Breathlessness on exertion is felt during physical activities. It is experienced as the sensation of running out of air and not being able to breathe. It causes symptoms like suffocation, labored breathing, tightness in the chest, palpitations, rapid and shallow breathing, wheezing, and coughing.
Severe cases of exertional dyspnea present with signs and symptoms like hypoxemia, hypotension, tracheal deviation, unstable dysrhythmia, altered mental status, stridor, cyanosis, intercostal indrawing, tripod positioning, use of accessory muscles for breathing, and absent breath sounds.
How Does Breathlessness on Exertion Occur?
Various physiological pathways can lead to breathlessness, including pathways via mechanoreceptors, lung receptors, and ASIC (acid-sensing ion channels) chemoreceptors. The afferent signals, efferent signals, and central information processing contribute to breathlessness. The ventral processing component in the brain compares the afferent and efferent signals. Breathlessness occurs when there is a mismatch between the afferent and efferent signals. It occurs when the afferent signal (need for ventilation) is not met by the efferent signal (physical breathing).
Afferent signals are sensory signals that travel toward the brain. Afferent neurons arise from the carotid bodies, medulla, lungs, and chest wall. Afferent neurons are critical in breathlessness. Chemoreceptors that are present in the carotid bodies and medulla deliver information regarding the blood gas levels of oxygen, carbon dioxide, and hydrogen. The juxtacapillary receptors in the lungs are sensitive to pulmonary interstitial edema, and stretch receptors signal the presence of bronchoconstriction. Muscle spindles in the chest wall signal the stretch and tension of the respiratory muscles. Hence, poor ventilation results in hypercapnia, left heart failure leading to impaired gas exchange, asthma that causes bronchoconstriction, and muscle fatigue that results in ineffective respiratory muscle action. All these factors contribute to dyspnea and dyspnea on exertion.
Efferent signals are motor neuron signals that travel to the respiratory muscles. The diaphragm is an important respiratory muscle. Other muscles of respiration include the external and internal intercostal muscles, abdominal muscles, and accessory respiratory muscles.
The brain compares the afferent information regarding ventilation with the current level of respiration determined by the efferent signals. Dyspnea occurs if the level of respiration is insufficient for the body’s status. Dyspnea can also be psychological in some cases, where the individuals are aware of their breathing but do not experience the distress of dyspnea.
What Are the Complications of Breathlessness on Exertion?
Breathlessness on exertion can progress and cause complications like a respiratory failure with hypoxia or hypercapnia. It further progresses to cause complications like respiratory or cardiac arrest or both.
How Is Breathlessness on Exertion Diagnosed?
The diagnosis is based on the evaluation of the airway, breathing, circulation, medical history, and examination. Various scales are used to quantify the degree of breathlessness. The MRC (medical research council) scale grades dyspnea based on the circumstances and severity of dyspnea.
- Blood Tests - Blood tests like D-dimer are performed to rule out pulmonary embolism, as it causes shortness of breath. Low levels of brain natriuretic peptides are used to rule out congestive heart failure, as a higher level indicates congestive heart failure.
- Radiographic Imaging - Chest X-ray is performed to rule out pneumothorax, pulmonary edema, or pneumonia. A spiral computed tomography scan with intravenous radiocontrast is performed to evaluate pulmonary embolism.
How Is Breathlessness on Exertion Treated?
Breathlessness during physical activity is normal, but if it occurs due to pathological causes, the treatment is based on the cause of breathlessness during exertion.
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Oxygen therapy is given to patients with hypoxia.
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Interventions with physiotherapy are useful for patients with dyspnea on exertion due to neurological or neuromuscular abnormalities.
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Medications like opioids, benzodiazepines, and steroids reduce exertional dyspnea due to cancerous or noncancerous causes.
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Nonpharmacological techniques like physical and mental relaxation techniques, energy conservation techniques, pacing techniques, and breathing exercises are also employed in managing breathlessness.
Conclusion
Breathlessness during exertion is a normal condition. It can be pathological due to underlying causes such as respiratory diseases, cardiac diseases, neuromuscular, psychogenic, or systemic illness or a combination of these conditions. It is important to consult the physician on experiencing breathing difficulties. Early diagnosis and management play a vital role in treating exertional dyspnea and its underlying cause.
