A pneumothorax occurs when the thoracic pleural pressure reaches around __ mmHg. A) 780 B) 760 C) 755 D) 0
The correct answer and explanation is:
The correct answer is D) 0.
A pneumothorax occurs when there is air or gas in the pleural space, leading to a collapse of the lung. The pleural pressure is typically subatmospheric, meaning it is lower than the atmospheric pressure (which is around 760 mmHg at sea level). This negative pressure is essential for keeping the lungs expanded and attached to the chest wall.
Under normal conditions, the pleural pressure remains around -4 to -5 mmHg relative to atmospheric pressure. When a pneumothorax occurs, air enters the pleural space, which can disrupt the negative pressure and cause the pressure to increase. If the pleural pressure rises to 0 mmHg, or equal to atmospheric pressure, the lung can no longer stay inflated and begins to collapse. This collapse occurs because the lung tissue cannot maintain the expansion force against the now-equalized pleural pressure.
The development of a pneumothorax can result from trauma, lung diseases, or even spontaneously in some individuals. This condition impairs gas exchange, making it difficult for the body to oxygenate the blood properly. Depending on the severity, a pneumothorax can be life-threatening, and medical intervention is often required to remove the air from the pleural space and restore normal lung function.
In summary, a pneumothorax leads to a loss of the negative pleural pressure, causing the pressure in the pleural space to rise to 0 mmHg, at which point the lung collapses.