Pneumothorax

Pneumothorax is the presence of air in the pleural cavity, which leads to partial or complete collapse of the lung. It can develop spontaneously or against the background of existing lung diseases, injuries or medical procedures. It is a sign of a violation of the lung hermeticity, which can occur with rupture of bullae and cysts in bullous emphysema, rupture in adhesive pleurodesis, failure of the stump after resections, with chest trauma due to rupture (in case of closed chest trauma) or injury (in case of penetrating chest trauma), damage or detachment of the bronchus.

Pneumothorax can be pure, when there is an accumulation of air only, and in combination with exudates, for example, hemopneumothorax. Diagnosis of pneumothorax is based on physical examination and chest X-ray. Most pneumothoraces require aspiration or drainage of the pleural cavity.

Intrapleural pressure is normally negative (less than atmospheric pressure); this ensures independent expansion of the lung when the chest expands. In pneumothorax, air enters the pleural cavity through a damaged chest wall or the lumen of the mediastinal organs. As a result, intrapleural pressure increases, which leads to limited expansion of the lungs.

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Causes of pneumothorax

Depending on the volume of lung collapse, pneumothorax can be small (up to 25%), medium (50-75%), total (100%) and tense, when there is a shift in the mediastinum. Depending on the type of air entering the pleural cavity and its movement in it, there are:

• closed pneumothorax with air entering from the bronchus into the pleural cavity during inhalation (the most favorable, but in the presence of inflammation of the bronchi, the pleural cavity can become infected);
• open pneumothorax, when there is sufficient communication between the pleural cavity and the surface of the chest and air enters it through the wound during exhalation (dangerous only due to infection);
• valve pneumothorax, when air from the bronchus enters the pleural cavity during inhalation, and during exhalation a piece of the lung or pieces of the bulla cover the opening in the bronchus and do not allow air to exit into the bronchial tree, collapsing more and more with each inhalation (the most dangerous type, since compression of the lung quickly increases with displacement of the mediastinum and development of pulmonary heart failure). Most often, pneumothorax is unilateral, but it can also be bilateral.

Types of pneumothorax include hemopneumothorax and pyopneumothorax, which are accompanied by the development of a pronounced cardiopulmonary syndrome, clinically resembling myocardial infarction, and respiratory failure. Pyopneumothorax develops when an abscess breaks through from the lung, when the bronchial stump fails after lung resection, and when a bronchopleural fistula is formed. In addition to the accumulation of pus, the collapse of the lung is ensured by the flow of air. Pyopneumothorax, especially in young children, must be differentiated from diaphragmatic hernia (signs of intestinal obstruction), lobar emphysema (with it there is a shift in the mediastinum). In adults, it is necessary to remember the possibility of a huge lung cyst, but there is no intoxication with it.

Primary spontaneous pneumothorax occurs in individuals without underlying lung disease, particularly tall, thin young adults under 20 years of age. It is thought to result from direct rupture of subpleural apical blebs or bullae due to smoking or hereditary factors. Pneumothorax usually occurs at rest, although some cases occur with exertion from reaching or stretching objects. Primary spontaneous pneumothorax may also occur during diving and high-altitude flying due to uneven pressure changes within the lung.

Secondary spontaneous pneumothorax occurs in individuals with underlying lung disease and is most often caused by ruptured blebs or bullae in patients with severe COPD (forced expiratory volume in 1 second < 1 L), Pneumocystis jiroveci (formerly called P. carinii) infection in patients with HIV infection, cystic fibrosis, or any other parenchymal lung disease. Secondary spontaneous pneumothorax is usually more serious than primary spontaneous pneumothorax because it occurs in older patients with less compensatory reserve of pulmonary and cardiac function.

Catamenial pneumothorax is a rare form of secondary spontaneous pneumothorax that develops within 48 hours of the onset of menstrual bleeding in premenopausal women and occasionally in postmenopausal women taking estrogens. It is caused by intrathoracic endometriosis, possibly due to migration of abdominal endometrium through diaphragmatic defects or by embolization of the pelvic veins. During menstruation, a defect is formed in the pleura as the endometrium is shed.

Traumatic pneumothorax is a common complication of blunt and penetrating chest wounds.

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Causes of spontaneous pneumothorax

Primary

Smoking-induced subpleural bullae rupture

Secondary

More often

• Bronchial asthma
• COPD
• Cystic fibrosis
• Necrotizing pneumonia
• Pneumocystis jiroveci (formerly called P. carinii) infection
• Tuberculosis

Less often

• Lung diseases
  • Idiopathic pulmonary fibrosis
  • Langerhans cell granulomatosis
  • Lung cancer
  • Lymphangioleiomyomatosis
  • Sarcoidosis
• Connective tissue diseases
  • Ankylosing spondylitis
  • Ehlers-Danlos syndrome
  • Marfan syndrome
  • Polymyositis/dermatomyositis
  • Rheumatoid arthritis
  • Sarcoma
  • Systemic sclerosis
  • Endometriosis of the thoracic cavity
  • Tuberous sclerosis

Tension pneumothorax is a pneumothorax that causes a progressive increase in intrapleural pressure to values exceeding atmospheric pressure throughout the respiratory cycle, resulting in lung collapse, mediastinal shift, and impaired venous return to the heart. Air continues to enter the pleural space but cannot escape. Without adequate treatment, the decreased venous return can cause systemic hypotension and respiratory and cardiac arrest within minutes. This condition usually occurs in patients on mechanical ventilation with positive expiratory pressure (especially during resuscitation). Rarely, it is a complication of traumatic pneumothorax, where a chest wall wound acts as a one-way valve that allows larger and larger volumes of air into the pleural space during inspiration, which cannot then escape.

Iatrogenic pneumothorax is caused by medical interventions including transthoracic needle aspiration, thoracentesis, central venous catheter placement, mechanical ventilation, and cardiopulmonary resuscitation.

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Symptoms of pneumothorax

The clinical picture depends on the degree of lung collapse, but is quite pronounced: chest pain is moderate, constant, the connection with breathing and coughing is weak, rapid breathing develops, with a collapse of more than 25% of the volume, shortness of breath, cyanosis of the face and lips appears.

The chest lags behind in the act of breathing on the side of the pneumothorax, the intercostal spaces bulge, especially with a deep breath and cough; with tension pneumothorax, it is swollen.

Percussion: with a collapse of up to 25% of the volume - bright tympanitis; with large volumes - a box sound. Auscultation: with a collapse of up to 25% of the volume - sharply weakened breathing; with large volumes - a "silent" lung. With tension pneumothorax, pronounced pulmonary-cardiac insufficiency with changes on the ECG similar to myocardial infarction.

Non-traumatic pneumothoraces are sometimes asymptomatic. In other cases, symptoms of pneumothorax such as dyspnea, pleuritic chest pain, and anxiety develop. Dyspnea may develop suddenly or gradually, depending on the rate of development and volume of pneumothorax. Pain may imitate myocardial ischemia, musculoskeletal lesions (with irradiation to the shoulder), or abdominal pathology (with irradiation to the abdomen).

Classic physical changes include absence of vocal fremitus, increased percussion sounds, and decreased breath sounds on the side of the pneumothorax. With significant pneumothorax, the affected side may be enlarged, and the trachea may be noticeably displaced to the opposite side.

Complications of pneumothorax

The three main problems encountered in the treatment of pneumothorax are air suction into the pleural cavity, failure to achieve lung expansion, and reventilation pulmonary edema.

Air is usually sucked into the pleural cavity through the primary defect, but may occur through the site of a chest tube if the wound is not properly sutured and sealed. It is more common in secondary than in primary spontaneous pneumothoraces. Most cases resolve spontaneously in less than 1 week.

Failure to re-expand the lung is usually due to persistent air in the pleural cavity, endobronchial obstruction, armored lung, or improper placement of the pleural drainage. If air in the pleural cavity or incomplete expansion persists for more than 1 week, thoracoscopy or thoracotomy is necessary.

Pulmonary edema occurs due to its overstretching and rapid expansion after an attempt to create negative pressure in the pleural cavity after the lung has been in a collapsed state for more than 2 days. Oxygen therapy, the use of diuretics, and supportive therapy for lung and heart function are effective.

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Diagnosis of pneumothorax

The diagnosis of "pneumothorax" is established on the basis of chest X-ray during inspiration in a vertical patient position, when accumulation of radiolucent air and absence of lung tissue in the space between the collapsed whole lung or its lobe and the parietal pleura are revealed. In large pneumothoraces, displacement of the trachea and mediastinum are also visualized.

The size of the pneumothorax is defined as the percentage of the volume of the hemithorax occupied by air and is calculated as 1 - the ratio of the lung width raised to the third power and the width of the affected hemithorax also raised to the third power. For example, if the width of the hemithorax is 10 cm and the width of the lung is 5 cm, the ratio of the cubes of these dimensions is 5/10 = 0.125. Thus, the size of the pneumothorax corresponds to: 1 - 0.125 = 0.875 or 87.5%. The presence of adhesions between the lung and the chest wall prevents symmetrical collapse of the lung, as a result of which the pneumothorax may appear atypical or divided into fragments, which interferes with calculations.

Of the instrumental studies, the most informative is chest X-ray (to determine the presence of a condition such as pneumothorax and the degree of lung collapse); thoracoscopy to identify the cause (if technical means are available, one-stage lung sealing is possible). To identify lung sealing and lung compression syndrome, a pleural puncture is performed. Tension pneumothorax is characterized by the fact that air enters under pressure. If the fistula in the lung has sealed itself, the air is removed with difficulty and the lung straightens out, which will be confirmed by a control X-ray.

Hemothorax and hemopneumothorax are accompanied by clinical features of exudative non-purulent pleurisy. Damage to the thoracic lymphatic duct is accompanied by the development of chylothorax, which clinically manifests itself as pleurisy, but when the pleural cavity is punctured, chylous (similar to a fat emulsion) fluid is obtained.

Initial differential diagnostics of damage is performed using chest X-rays. Pleural puncture with laboratory testing of exudate is a mandatory condition for differential diagnostics of the pathological process. Thoracoscopy provides the highest diagnostic effect.

Detection of small pneumothoraces is sometimes difficult on chest radiography. Conditions that have identical radiographic features include emphysematous bullae, skin folds, and superposition of gastric or intestinal shadows on the lung fields.

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Treatment of pneumothorax

Dry pleurisy and non-purulent exudative small volumes are treated on an outpatient basis or in a therapeutic hospital. Exudative pleurisy of large volumes and purulent pleurisy, hemopleurisy and hemothorax, pneumothorax, including traumatic injuries, are the competence of thoracic surgeons, and the patient should be hospitalized in a specialized department.

Oxygen therapy should be given before chest radiography is performed; oxygen accelerates pleural reabsorption of air. Treatment of pneumothorax depends on the type, size, and clinical manifestations of the pneumothorax. Primary spontaneous pneumothoraces that are less than 20% in size and do not cause respiratory or cardiovascular manifestations may resolve safely without treatment if follow-up chest radiographs performed approximately 6 and 48 hours later show no progression. Large or symptomatic primary spontaneous pneumothoraces should be evacuated by pleural drainage.

Drainage is accomplished by inserting a small-bore intravenous needle or pigtail catheter into the second intercostal space at the midclavicular line. The catheter is connected to a three-way adapter and syringe. Air is withdrawn from the pleural space through the adapter into the syringe and removed. The process is repeated until the lung re-expands or until 4 L of air have been removed. If the lung re-expands, the catheter can be removed, but it may be left in place after a one-way Heimlich valve has been attached (allowing patient ambulation). If the lung does not re-expand, pleural drainage is necessary; in either case, patients are usually admitted to the hospital for observation. Primary spontaneous pneumothorax may be treated with initial placement of a chest tube connected to a water-filled container and possibly a suction device. Patients developing primary spontaneous pneumothorax should be advised to stop smoking, as smoking is a major risk factor for this condition.

Secondary and traumatic pneumothoraces are usually treated with pleural drainage, although some cases of small pneumothoraces may be treated on an outpatient basis. In symptomatic iatrogenic pneumothoraces, aspiration is the most appropriate treatment.

Tension pneumothorax is an emergency. Treatment of pneumothorax should begin immediately by inserting a 14 or 16 gauge needle into the 2nd intercostal space at the midclavicular line, which is then connected to a catheter. The sound of air escaping under pressure confirms the diagnosis. The catheter may be left open or attached to a Heimlich valve. Emergency decompression should be completed by inserting a thoracostomy tube, after which the catheter is removed.

How to prevent pneumothorax?

Recurrence occurs within 3 years of the initial spontaneous pneumothorax in about 50% of cases; pneumothorax is best prevented by video-assisted thoracoscopic surgery, which includes suturing of the bullae, pleurodesis, parietal pleurectomy, or talc injection; thoracotomy is still performed in some centers. These procedures are recommended when pleural drainage fails in spontaneous pneumothorax, in recurrent pneumothoraces, or in patients with secondary spontaneous pneumothorax. The recurrence rate after these procedures is less than 5%. When thoracoscopy is not possible, chemical pleurodesis via a chest tube is an option. This procedure, although much less invasive, reduces the recurrence rate by only about 25%.