Final answer:
Obstructive lung conditions feature decreased FEV1 and peak expiratory flow rate, and a low FEV1/FVC ratio, reflecting the difficulty in exhaling due to airway obstruction.
Step-by-step explanation:
In obstructive lung conditions, which are characterized by a constriction or blockage of the airways that results in difficulty exhaling, we typically see certain characteristic changes in pulmonary function test (PFT) parameters. One key finding is a decreased FEV1, which stands for Forced Expiratory Volume in 1 second, and indicates the volume of air a person can forcibly exhale in one second. A decreased FEV1/FVC ratio, where FVC denotes Forced Vital Capacity, is also commonly observed. This ratio is used to distinguish between obstructive and restrictive lung disease, with a low ratio (< 69 percent) being indicative of obstructive disease like asthma. Additionally, there is often a decreased peak expiratory flow rate, which is the maximum speed of exhalation. However, total lung capacity may be normal or sometimes increased due to air trapping within the lungs. In the instance of obstructive lung conditions, the airway resistance makes it difficult for patients to fully expel air from their lungs.