Final answer:
A young adult with an FEV1/FVC ratio of 65% would be interpreted as having obstructive lung disease, since the ratio is below the 69 percent threshold generally associated with obstruction, as opposed to restrictive lung diseases which present with higher ratios.
Step-by-step explanation:
The FEV1/FVC ratio is a critical measurement in assessing lung function, specifically in diagnosing restrictive or obstructive lung diseases. A young adult with an FEV1/FVC ratio of 65% is indicative of obstructive lung disease. This is because individuals with obstructive lung disease typically have an FEV1/FVC ratio less than 69 percent, whereas those with restrictive lung disease generally have higher ratios in the range of 88 to 90 percent. Determining this ratio is essential as it can differentiate between airflow obstruction, as seen in conditions like asthma or emphysema, and the reduced lung volumes seen in diseases like fibrosis where the lung tissues are stiff.
In obstructive diseases, the ratio is low due to resistance to airflow caused by conditions such as asthma, which makes exhalation difficult. Conversely, a high FEV1/FVC ratio suggests that the patient has lung fibrosis or stiff lungs that cannot expand well, but remain unobstructed and thus expel air quickly. Spirometry is the technique used to measure these lung volumes and ratios.