What Is Pleural Fluid?

Pleural fluid: The pleural cavity is a closed cavity composed of the parietal pleura and the visceral pleura. Inside it is negative pressure. Under normal circumstances, there is a small amount (about 1 ~ 30 ml) of liquid between the two layers of pleura to lubricate. Effect, reducing the friction between the two layers of pleura during the respiratory activity, which is conducive to the lungs contraction and contraction in the chest cavity. This fluid is produced from the parietal pleura and absorbed by the visceral pleura. It is in dynamic equilibrium with constant circulation, and the amount of fluid remains constant. When something happens that affects the pleura, whether the pleural fluid produced by the parietal pleura or the rate of pleural pleural absorption of the pleural fluid changes, it can increase the fluid in the pleural cavity, which is called pleural effusion (effusion).

Pleural fluid

Pleural fluid: The pleural cavity is a closed cavity composed of the parietal pleura and the visceral pleura. Inside it is negative pressure. Under normal circumstances, there is a small amount (about 1 ~ 30 ml) of liquid between the two layers of pleura to lubricate. Effect, reducing the friction between the two layers of pleura during the respiratory activity, which is conducive to the lungs contraction and contraction in the chest cavity. This fluid is produced from the parietal pleura and absorbed by the visceral pleura. It is in dynamic equilibrium with constant circulation, and the amount of fluid remains constant. When something happens that affects the pleura, whether the pleural fluid produced by the parietal pleura or the rate of pleural pleural absorption of the pleural fluid changes, it can increase the fluid in the pleural cavity, which is called pleural effusion (effusion).

Pharmacological action

In the past, the exchange of pleural effusion was completely determined by the pressure difference between hydrostatic pressure and colloid osmotic pressure. Animals with thin visceral pleura (such as rabbits) have wall pleura mainly supplied by intercostal arteries, high capillary pressure, and dirty The pleura is supplied by the pulmonary arteries and the capillaries are low, so driven by the pressure, the liquid is filtered from the parietal pleura into the pleural cavity, and the visceral pleura absorbs the pleural fluid at a similar pressure. However, since the 1980s, it has been found that there are lymphatic micropores in the parietal pleural mesothelial cells of animals (including humans) with thick visceral pleura. The visceral pleura is supplied by systemic bronchial arteries and pulmonary circulation. A consensus was reached on the mechanism of pleural effusion production and absorption, that is, pleural effusion enters the pleural cavity from leaky pleura into the pleural cavity due to pressure gradient from the systemic circulation vessels of the parietal and visceral pleura, and then through the lymphatic micropores of the pleural wall Lymphatic reabsorption, this form is similar to any interstitial cavity of the body. Visceral pleura has less effect on pleural fluid circulation under normal circumstances

Pleural effusion

Hydrothorax can be divided into exudative and leaky in nature. Exudative causes are many and can be summarized into two categories: one is caused by inflammatory lesions, such as infectious inflammation caused by infection of the pleura by bacteria, viruses or fungi, resulting in pleural effusion, or due to pulmonary embolism, pancreatitis And connective tissue diseases such as non-infectious inflammation cause pleural effusion; the second type is tumorous, such as cancer growing in the pleura or metastasis and invasion of the pleura causing effusion, which can be seen in pleural mesothelioma, lung cancer, breast cancer, gastric cancer . The cause of leaky pleural effusion can be a systemic disease, such as hypoproteinemia, allergic disease, or a disease of an organ, such as congestive heart failure, liver cirrhosis, amoebic liver disease, ruptured thoracic duct Wait.

Clinical manifestations of pleural effusion

Pleural fluid (a) symptoms

Dyspnea is the most common symptom, often accompanied by chest pain and cough. Dyspnea is associated with decreased compliance with the thorax, compression of the diaphragm on the affected side, displacement of the mediastinum, and decreased lung volume to stimulate nerve reflexes. The symptoms vary depending on the cause. Tuberculous pleurisy is more common in young people, and often has fever, dry cough, and chest pain. With the increase of pleural fluid, chest pain can be relieved, but chest tightness and shortness of breath can occur. Malignant pleural effusion is more common in middle-aged and older patients, and generally has no fever, chest pain, and symptoms of weight loss and tumors in the respiratory tract or primary site. The inflammatory effusion is mostly exudative, often accompanied by cough, sputum, chest pain and fever. Pleural effusion caused by heart failure is leakage, and other manifestations of cardiac insufficiency. The right pleural effusion associated with liver abscess can be reactive pleurisy or empyema with fever and pain in the liver area. Symptoms are also related to the amount of effusion. When the amount of effusion is less than 0.3-0.5L, the symptoms are not obvious, and palpitations and dyspnea are more obvious when there is a large amount of effusion.

Pleural fluid (two) signs

Related to the amount of effusion. When there is a small amount of fluid, there are no obvious signs, or you can touch the pleural friction and smell the pleural friction sound. When there is a large amount of effusion, the ipsilateral thorax is full, the tactile tremor is weakened, dullness is caused by local percussion, and respiratory sounds are reduced or disappeared. May be accompanied by tracheal, mediastinal displacement to the healthy side. Extrapulmonary diseases, such as pancreatitis and rheumatoid arthritis, often cause signs of pleural effusion.