Final answer:
Obstructive lung diseases, including emphysema, asthma, and pulmonary edema, lead to decreased airflow due to the destruction of alveolar walls, increased inflammation, and airway obstruction, resulting in a reduced FEV1/FVC ratio for diagnosis.
Step-by-step explanation:
Obstructive lung diseases, such as emphysema, asthma, and pulmonary edema, are characterized by decreased airflow due to airway obstruction. In emphysema, commonly caused by smoking, the alveolar walls are destroyed, reducing the surface area for gas exchange and increasing lung compliance due to a loss of elastic fibers, leading to air trapping. Asthma is triggered by environmental factors, causing inflammation and obstruction in the airways through fluid accumulation, bronchiole smooth muscle spasms, or increased mucus secretion.
This results in difficulty expelling air, leading to a high lung volume to compensate for the obstruction. The FEV1/FVC ratio, where FEV1 is the amount of air that can be forcibly exhaled in one second and FVC is the total amount of air expelled, can diagnose restrictive versus obstructive lung diseases, with the ratio being lower in obstructive conditions.