Dyspnea on exertion

Introduction Labor-induced dyspnea: Beginning with shortness of breath after intense activity or physical labor, such as an upset when going on a building, going uphill, or going straight on the ground. As the degree of congestion of the lungs increases, it can gradually develop into lighter activities or physical labor, and even when resting, breathing difficulties occur. Dyspnea is the earliest and most common symptom of left heart failure, including labor dyspnea, sitting breathing and paroxysmal nocturnal dyspnea.

Cause

The first thing that occurs with cardiogenic dyspnea is exertional dyspnea. Acute or chronic pulmonary blood stasis and decreased lung capacity also cause labor dyspnea.

Cardiac dyspnea is mainly caused by left heart and/or right heart failure. The mechanism of the two is different. The dyspnea caused by left heart failure is more serious.

The main cause of dyspnea in left heart failure is pulmonary congestion and decreased alveolar elasticity. The mechanism is:

1 pulmonary congestion, so that the gas diffusion function is reduced.

2 The alveolar tension is increased, the stretch receptor is stimulated, and the respiratory center is excited by the vagus nerve.

3 Alveolar elasticity decreases, its expansion and contraction ability is reduced, and lung capacity is reduced.

4 Reflex sensitivity of the pulmonary circulation to the respiratory center.

The dyspnea caused by left heart failure is characterized by the appearance or aggravation during activities, the reduction or relief at rest, the increase in supine position, and the reduction in sitting position. As the activity increases, the body's oxygen consumption increases; when sitting, the lower body returns to reduce the amount of blood and reduce the degree of pulmonary congestion; while sitting, the position of the sputum is reduced, the diaphragm activity is increased, and the vital capacity can be increased by 10% to 30%. Patients with more severe conditions are often forced to take a semi-sitting position or sitting orthopenea.

In acute left heart failure, paroxysmal dyspnea often occurs, which occurs during nighttime sleep, which is called paroxysmal nocturnal dyspnea. The mechanism of occurrence is as follows: (1) increased vagal excitability during sleep, coronary artery contraction, decreased myocardial blood supply, and decreased cardiac function. 2 small bronchiectasis, alveolar ventilation decreased. 3 When the supine position is reduced, the lung capacity is reduced, and the blood volume of the lower body is increased, resulting in increased pulmonary congestion. 4 The sensitivity of the respiratory center is reduced, and the mild hypoxia response caused by pulmonary congestion is slow. When the degree of congestion is increased and the hypoxia is obvious, the respiratory center is stimulated to respond. At the time of the attack, the patient often wakes up in the chest and feels awkward and awkward. He is forced to sit up, panic and panic, accompanied by a cough. After a few minutes to tens of minutes, the symptoms gradually relieve and relieve. The severe person is highly asthmatic, and his face is blue and purple. Sweat, breathing has a wheezing sound, coughing liquid pink foam-like sputum, there are more wet rales at the bottom of both lungs, heart rate increases, there is galloping. This type of dyspnea, also known as "cardiac asthma," is common in hypertensive heart disease, coronary heart disease (coronary heart disease), rheumatic heart valve disease, myocarditis, and cardiomyopathy.

The cause of difficulty in breathing during right heart failure is mainly caused by systemic congestion. The mechanism of occurrence is as follows: 1 The right atrium and the superior vena cava are elevated, and the baroreceptor is stimulated to excite the respiratory center. 2 blood oxygen content decreased, and acidic metabolites such as lactic acid and pyruvic acid increased, stimulating the respiratory center. 3 Congestive hepatomegaly, ascites and pleural effusion, which restricts respiratory movement and reduces the area of gas exchange in the lungs. Clinically mainly seen in chronic pulmonary heart disease, exudative or constrictive pericarditis, no right heart failure, the main mechanism of dyspnea is due to a large number of pericardial effusion caused by pericardial tamponade or pericardial fibrous thickening, calcification, contraction Narrow, limited diastolic heart, caused by systemic venous congestion.

an examination

Related inspection

Thoracic fluoroscopy myocardial perfusion imaging

First, the patient has a serious history of heart disease.

Second, mixed dyspnea, lying and obvious at night.

Third, the middle of the lungs may appear medium and small wet voice, and change with body position.

Fourth, X-ray examination: abnormal changes in heart shadow, congestion in the hilar and its vicinity or both pulmonary edema.

Fifth, congestive heart failure: dyspnea is the earliest main symptom.

Sixth, pericardial effusion: any cause of acute or chronic pericarditis occurs when a large amount of fluid, compression of the bronchi and lungs and cause breathing difficulties.

Differential diagnosis

Cardiogenic dyspnea is easily confused with the following symptoms:

1, pulmonary dyspnea

Caused by respiratory disease, mainly in the following three forms:

Inspiratory dyspnea: manifested as wheezing, inspiratory sternum, supraclavicular fossa and rib gap depression - three concave sign. Common in the throat, tracheal stenosis, such as inflammation, edema, foreign bodies and tumors.

Expiratory dyspnea: prolonged expiration with wheezing, seen in bronchial asthma and obstructive pulmonary disease.

Mixed dyspnea: seen in pneumonia, pulmonary fibrosis, massive pleural effusion, pneumothorax, etc.

2, toxic breathing difficulties

Acidosis caused by various reasons can increase blood carbon dioxide, lower pH, stimulate peripheral chemoreceptors or directly stimulate the respiratory center, increase respiratory ventilation, and manifest as deep and large breathing difficulties; respiratory inhibitors such as morphine In the case of poisoning such as barbiturates, the respiratory center can also be suppressed, making breathing shallow and slow.

3, blood-borne dyspnea

Severe anemia can be caused by red blood cell reduction, hypoxia and hypoxia, especially after activity; hemorrhage is caused by ischemia and blood pressure during hemorrhage or shock, which stimulates the respiratory center.

4, neuropsychiatric and myopathy dyspnea

Severe brain diseases such as encephalitis, cerebrovascular accidents, brain tumors, etc. directly involve the respiratory center, abnormal respiratory rhythms, resulting in difficulty breathing; myasthenia gravis crisis causes respiratory muscle paralysis, leading to severe breathing difficulties. In addition, snoring can also have dyspnea episodes, which are characterized by frequent respiratory rate and superficial stagnation, as respiratory sputum poisoning is often accompanied by hand and foot snoring.

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