Causes and manifestations of tension pneumothorax

Tension pneumothorax often presents with extreme dyspnea, orthopnea, irritability, and even coma and suffocation. We must be vigilant when these symptoms occur and understand the cause so that we can focus on prevention and treatment.

1. Causes

Tension pneumothorax refers to a one-way valve-like air leakage channel in the pleural cavity. During inhalation, the pressure in the pleural cavity decreases, the valve opens, and gas enters; during exhalation, the pressure in the pleural cavity increases, the valve closes, and the gas cannot be discharged. The wounds of the lungs, bronchi, and chest wall caused by traumatic pneumothorax can act as single-channel valves, and the pleural rupture caused by spontaneous pneumothorax can also form such valves.

2. Clinical manifestations

The patient presented with extreme dyspnea and orthopnea. People with severe hypoxia may experience cyanosis, irritability, coma, and even suffocation. Physical examination revealed fullness of the chest on the injured side, widened intercostal spaces, decreased respiratory amplitude, and possible subcutaneous emphysema. Percussion is tympanic. Breath sounds disappeared on auscultation. Chest X-ray examination showed a large amount of air accumulation in the pleural cavity, the lung may be completely collapsed, and the trachea and heart shadows are shifted to the healthy side. When the pleural cavity is punctured, high-pressure gas rushes out. After passing gas, the symptoms improve, but may worsen again soon. Such manifestations also help with diagnosis. Severe chest injuries, such as the rapid onset of signs of tension pneumothorax, should lead to suspected bronchial rupture and prompt rescue, even thoracotomy.

3. Inspection

1. X-ray manifestations

A chest X-ray can show the degree of lung collapse, lung condition, presence or absence of pleural adhesions, pleural effusion, and mediastinal shift. The chest X-ray shows a pleural air accumulation zone with a uniform radiolucent area without lung texture, and the inner side is an arc-shaped linear lung edge parallel to the chest wall. A small amount of gas is confined to the upper part of the chest cavity, which is often covered by bones. Ask the patient to exhale deeply to make the collapsed lung smaller and denser, forming a clear contrast with the outer air-translucent area, thus showing the pneumothorax band. In case of massive pneumothorax, the affected lung is compressed and gathers in the hilar area as a spherical shadow. The patient's X-ray showed bullae at the apex of the lung; when hemothorax was present, a fluid-air plane could be seen; when adhesions existed in the chest, the collapsed lung lost its uniform compression toward the hilum, showing irregular compression or lobed edges of the lung compression; the diaphragm on the affected side moved downward, and the trachea and heart shifted toward the healthy side; when combined with mediastinal emphysema, mediastinal and subcutaneous air shadows could be seen.

2. Chest CT scan

It can clearly show the scope of pleural effusion, the amount of air accumulated, the degree of lung compression, or the presence of bullae at the apex of the lung. Chest CT can also show the amount of pleural effusion. Especially for pneumothorax with small air content and localized pneumothorax mainly located in the anterior and middle pleural cavity, it is easy to miss the diagnosis on X-ray chest images, while CT has the weakness of no image overlap and can make a clear diagnosis.