What is a closed pneumothorax? What is an open pneumothorax?

Accumulation of air in the pleural cavity is called pneumothorax. Pneumothorax is mostly caused by rupture of lung tissue, trachea, bronchi, or esophagus, allowing air to escape into the pleural cavity, or by a wound in the chest wall that pierces the pleura, causing the pleural cavity to communicate with the outside world and allowing outside air to enter. So what is a closed pneumothorax?

1. Closed pneumothorax

In a closed pneumothorax, the intrathoracic pressure remains below atmospheric pressure. The amount of air in the pleural cavity determines the degree of collapse of the injured lung. As air accumulates in the chest cavity and the lung collapses, the crack on the lung surface shrinks until it does not open during inhalation, and the pneumothorax tends to stabilize. The collapse of the injured lung reduces the lung's respiratory area, which will affect the lung's ventilation and gas exchange functions, and the ventilation-perfusion ratio will also be unbalanced. Increased intrathoracic pressure on the injured side can cause the mediastinum to shift toward the healthy side. Depending on the amount and speed of air accumulation in the pleural cavity, patients may show no symptoms in mild cases, while patients may have obvious breathing difficulties in severe cases. Physical examination may reveal a full chest, decreased respiratory activity, displacement of the trachea toward the unaffected side, a tympanic sound to percussion of the injured chest, and decreased breath sounds. Chest X-ray examination can show varying degrees of lung collapse and pleural air, sometimes accompanied by a small amount of pleural effusion.

Patients with pneumothorax for a long time and with a small amount of accumulated air do not need special treatment, as the accumulated air in the chest cavity can usually be absorbed on its own within 1 to 2 weeks. A large pneumothorax requires pleural puncture to drain the accumulated air, or closed chest drainage to promote early expansion of the lungs, and antibiotics to prevent infection.

2. Open pneumothorax

When an open pneumothorax is formed, external air can freely enter and exit the pleural cavity through chest wall wounds or soft tissue defects during breathing. The amount of air in and out is closely related to the size of the chest wall wound. When the wound is larger than the tracheal diameter, the amount of air in and out is large, the intrathoracic pressure is almost equal to the atmospheric pressure, and the injured lung will completely collapse and lose its respiratory function. The intrathoracic pressure on the affected side is significantly higher than that on the healthy side, and the mediastinum shifts toward the healthy side, further limiting the expansion of the healthy lung. During inhalation and exhalation, the pressure in the pleural cavity on both sides is unbalanced and changes periodically, causing the mediastinum to move toward the healthy side during inhalation and toward the injured side during exhalation. This is called mediastinal flutter. Mediastinal flutter and displacement affect venous return to the heart, causing circulatory disorders.

The injured person had obvious breathing difficulties, flaring nostrils, cyanosis of the lips, and distended jugular veins. A wound with a sucking sound as air moves in and out of the chest cavity can be seen on the injured side of the chest wall, which is called a sucking wound. The trachea is displaced to the healthy side, there is a tympanic sound when percussing the chest on the injured side, breath sounds disappear, and in severe cases, shock occurs. Chest X-ray examination showed a large amount of air accumulation in the injured side of the chest cavity, lung collapse, and mediastinum shifted toward the healthy side.

The key points of first aid treatment for open pneumothorax are: immediately convert the open pneumothorax into a closed pneumothorax, gain time to save lives, and quickly transfer to the hospital. Use sterile dressings such as vaseline gauze, gauze, cotton pads or clean equipment such as plastic bags, clothes, bowls and cups to make airtight dressings and compression materials. When the injured person exhales forcefully, suck the wound to seal it and apply pressure bandage. If the casualty's breathing becomes more severe or there are signs of tension pneumothorax during transfer, high-pressure gas will be used. Further treatment after being sent to the hospital is: give oxygen, replenish blood volume, correct shock; clean and suture the chest wall wound, and perform closed chest drainage; give antibiotics, encourage the patient to cough and expectorate, and prevent infection; if there is suspected damage to the internal organs in the chest or progressive bleeding, open chest exploratory surgery is required.

The indications for closed chest drainage are: ① moderate to large pneumothorax, open pneumothorax, tension pneumothorax; ② patients whose lungs cannot be expanded after thoracentesis; ③ patients with pneumothorax or hemothorax who require mechanical ventilation or artificial ventilation; ④ patients with recurrence of pneumothorax or hemothorax after removal of the chest drainage tube; ⑤ thoracotomy. The method is: determine the location of intubation based on clinical diagnosis. Pneumothorax drainage is generally in the 2nd intercostal space on the mid-axillary line of the anterior chest wall, and hemothorax is in the 6th or 7th intercostal space between the mid-axillary line and the posterior axillary line. After disinfection, perform local infiltration anesthesia on the entire layer of the local chest wall, cut the skin, bluntly separate the muscle layer, open the closed dressing through the upper edge of the ribs when the injured person exhales, and drain the closed pleural drainage and insert a chest drainage tube with a side hole. The side hole of the drainage tube should be 2 to 3 cm deep into the chest cavity. The drainage tube is connected to a closed drainage device to ensure that the air and liquid in the chest cavity can overcome the pressure of 0.3~0.4 kPa (3~4 crlH20) and can be drained out of the chest cavity smoothly, while the external air and liquid will not be inhaled into the chest cavity. After surgery, the drainage tube was squeezed frequently to keep the lumen open, and the drainage volume was recorded every hour or 24 hours. After drainage, the lungs expand well, and no gas or fluid is discharged. The drainage tube can be removed and the wound can be closed when the patient takes a deep breath and holds his breath.