Primary spontaneous pneumothorax (PSP) has for many years been thought to be caused by "blebs" (small air-filled lesions just under the pleural surface), which were presumed to be more common in those classically at risk of pneumothorax (tall males) due to mechanical factors. In PSP, blebs can be found in 77% of cases, compared to 6% in the general population without a history of PSP. As these healthy subjects do not all develop a pneumothorax later, the hypothesis may not be sufficient to explain all episodes; furthermore, pneumothorax may recur even after surgical treatment of blebs. It has therefore been suggested that PSP may also be caused by areas of disruption (porosity) in the pleural layer, which are prone to rupture. Smoking may additionally lead to inflammation and obstruction of small airways, which account for the markedly increased risk of PSPs in smokers. Once air has stopped entering the pleural cavity, it is gradually reabsorbed.Tension pneumothorax occurs when the opening that allows air to enter the pleural space functions as a one-way valve, allowing more air to enter with every breath but none to escape. The body compensates by increasing the respiratory rate and tidal volume (size of each breath), worsening the problem. Unless corrected, hypoxia (decreased oxygen levels) and respiratory arrest eventually follow. Diagnosis
The symptoms of pneumothorax can be vague and inconclusive, especially in those with a small PSP; confirmation with medical imaging is usually required.
Rarely, there may be cyanosis (bluish discoloration of the skin due to low oxygen levels), altered level of consciousness, a hyperresonant percussion note on examination of the affected side with reduced expansion and decreased movement, pain in the epigastrium (upper abdomen), displacement of the apex beat (heart impulse), and resonant sound when tapping the sternum.Tension pneumothorax may also occur in someone who is receiving mechanical ventilation, in which case it may be difficult to spot as the person is typically receiving sedation; it is often noted because of a sudden deterioration in condition. Recent studies have shown that the development of tension features may not always be as rapid as previously thought. Deviation of the trachea to one side and the presence of raised jugular venous pressure (distended neck veins) are not reliable as clinical signs. Cause
Primary spontaneous
Spontaneous pneumothoraces are divided into two types: primary, which occurs in the absence of known lung disease, and secondary, which occurs in someone with underlying lung disease. The cause of primary spontaneous pneumothorax is unknown, but established risk factors include being of the male sex, smoking, and a family history of pneumothorax. Smoking either cannabis or tobacco increases the risk. The various suspected underlying mechanisms are discussed below. Secondary spontaneous
Secondary spontaneous pneumothorax occurs in the setting of a variety of lung diseases. The most common is chronic obstructive pulmonary disease (COPD), which accounts for approximately 70% of cases.