Final answer:
A collapsed lung is called a spontaneous pneumothorax, often associated with restrictive lung diseases like pulmonary fibrosis or respiratory distress syndrome, which reduce lung compliance and Forced Vital Capacity (FVC).
Step-by-step explanation:
A collapsed lung is medically termed a spontaneous pneumothorax.
In pulmonary fibrosis and respiratory distress syndrome, which are examples of restrictive lung diseases, the airways are less compliant due to stiff or fibrotic lung tissue. This results in less air movement and a greater positive intrapleural pressure, causing airway collapse during exhalation and trapping air in the lungs.
Such conditions greatly reduce the Forced Vital Capacity (FVC), which is the volume of air that can be forcibly breathed out after full inhalation.
It is important to note that diseases like COPD, previously known as chronic bronchitis or emphysema, also lead to significant lung damage and decreased elasticity of the alveoli, which hampers the ability to fully exhale air, leading to trapped air similarly to a collapsed lung.