Spontaneous pneumothorax can be differentiated into primary and secondary types. Primary spontaneous pneumothorax is defined as occurring spontaneously in patients without underlying lung disease. However, visible subpleural blebs or apical subpleural emphysema have been demonstrated retrospectively in the majority of patients who underwent thoracotomy or diagnostic computer tomography. Smoking is the most likely risk factor for primary spontaneous pneumothorax. It is assumed to cause inflammation of the small airways with secondary increase of airway resistance and development of emphysematous cysts by air trapping.
Secondary spontaneous pneumothorax is a complication of many lung diseases, mainly chronic obstructive pulmonary disease, cystic fibrosis and, more recently, AIDS. In chronic obstructive pulmonary disease, airway inflammation increases airway resistance which results in hyperinflation with intrinsic positive end-expiratory pressure (PEEP). Subsequently, pulmonary emphysema and thinning of the lung parenchyma occur. If the transpleural pressure gradient exceeds a certain level because of a high intrinsic PEEP, the overdistended emphysematous bulla and visceral pleura rupture, causing pneumothorax. As severity of chronic obstructive pulmonary disease and level of intrinsic PEEP are closely related, the risk of secondary spontaneous pneumothorax is higher in patients with chronic obstructive pulmonary disease who are more critically ill. Pneumocystis carinii pneumonia, treatment with inhaled pentamidine, and cigarette smoking are risk factors for spontaneous pneumothorax in AIDS patients. The pathomechanism appears to be necrosis of subpleural lung cavities.
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If you suffer with asthma, you will no doubt be familiar with the uncomfortable sensations as your bronchial tubes begin to narrow and your muscles around them start to tighten. A sticky mucus known as phlegm begins to produce and increase within your bronchial tubes and you begin to wheeze, cough and struggle to breathe.