Final answer:
In rheumatoid arthritis interstitial lung disease, FEV1 represents the amount of air expelled in one second, FVC is the total exhaled air during a forced breath, and the FEV1/FVC ratio helps in distinguishing between restrictive and obstructive lung diseases, usually showing a normal or elevated ratio in restrictive diseases like RA interstitial lung disease.
Step-by-step explanation:
In patients with rheumatoid arthritis interstitial lung disease, FEV1 (Forced Expiratory Volume in one second) is a measure of how much air a person can exhale in one second after a deep breath, while FVC (Forced Vital Capacity) is the total amount of air exhaled during a forced breath. The FEV1/FVC ratio is a crucial diagnostic indicator used to distinguish between restrictive lung disease (such as interstitial lung disease) and obstructive lung patterns. In restrictive lung diseases associated with conditions like rheumatoid arthritis, while the FVC is reduced, the airways are not as obstructed, resulting in a closer to normal or sometimes high FEV1/FVC ratio.
Specifically, in the context of rheumatoid arthritis interstitial lung disease, the FVC tends to be decreased because of the restrictive nature of the disease on lung volume. Conversely, because the airways are relatively unobstructed, the FEV1 may be only mildly reduced, leading to a normal or elevated FEV1/FVC ratio. This contrasts with obstructive diseases, where this ratio is decreased due to the airway obstruction impairing both FEV1 and FVC.