Final answer:
Primary spontaneous pneumothorax introduces air into the pleural space, negating the negative pressure needed to keep the lungs expanded and thus impairing lung capacity and gas exchange.
Step-by-step explanation:
Primary spontaneous pneumothorax occurs when air enters the pleural space spontaneously, without any apparent cause, often related to subtle abnormalities in connective tissue. This condition can considerably compromise the function of the pleural space and the mechanics of breathing.
In a healthy state, competing forces within the thorax create negative intrapleural pressure that facilitates lung inflation. The lung elasticity and surface tension of the alveolar fluid exert an inward pull, while the pleural fluid and thoracic wall exert an outward pull. This balance maintains the lungs in a slightly expanded state.
During primary spontaneous pneumothorax, this balance is disrupted. The introduction of air into the pleural space can negate the negative pressure, causing a part of the lung to collapse. This can reduce lung capacity and impair the efficient exchange of gases. Additionally, the thoracic wall compliance, which is necessary for the lungs to expand during inhalation, can be hampered by a collapsed lung since the chest cavity can no longer change volume-pressure appropriately.