Final answer:
Restrictive lung diseases like pulmonary fibrosis show reduced FVC with a normal or high FEV1/FVC ratio on PFTs due to reduced lung compliance without airway obstruction.
Step-by-step explanation:
A pulmonary function test (PFT) can indicate a restrictive lung disease such as respiratory distress syndrome or pulmonary fibrosis. These conditions are characterized by less compliant, stiff, or fibrotic airways, leading to decreased elasticity of the lung tissue which hinders normal lung expansion. A key indicator of restrictive disease on a PFT is a reduced forced vital capacity (FVC), which is the amount of air expelled from the lungs after taking the deepest breath possible. Unlike obstructive lung diseases, where the FEV1/FVC ratio decreases due to airway obstruction, in restrictive diseases, the FEV1/FVC ratio typically remains normal or high (88 to 90 percent) because the airways are not obstructed, although the volume of air is reduced.
The amount of air that can be forcibly exhaled after a deep breath. Additionally, the time it takes to exhale most of the air is greatly prolonged. A diagnosis of a restrictive disease can be made using a nebulizer or spirometry to detect the rate at which air is expelled from the lungs.Bother restrictive and obstructive lung diseases can be diagnosed using spirometry, part of the PFT, which measures the rate at which air can be expelled from the lungs. For restrictive lung diseases, FVC is decreased, but the air can still be expelled at a relatively normal speed, thus having a less impacted FEV1/FVC ratio compared to obstructive lung disease.