Question

which of the following is associated with obstructive pulmonary disease?
both the fev₁/fvc ratio is less than 75%, and the fvc is reduced
fev₁/fvc ratio is greater than 75%, but fvc is reduced
fev₁/fvc ratio is greater than 75%
fev₁/fvc ratio is less than 75%

Explanation:

Obstructive pulmonary disease is characterized by airflow limitation. The key diagnostic parameter is the \(FEV_1/FVC\) ratio. A ratio less than 75% (in some standards, often 70% is used as a cutoff, but if 75% is the reference in this context) indicates obstructive pattern. FVC (forced vital capacity) may be normal or reduced in obstructive diseases (in some cases like severe emphysema, FVC can be reduced due to hyperinflation and loss of lung elastic recoil, but the primary and most consistent indicator for obstruction is the low \(FEV_1/FVC\) ratio). The first option wrongly states that both are always the case (FVC reduction is not an essential diagnostic criterion for obstruction - it's more about the ratio). The second and third options have incorrect \(FEV_1/FVC\) ratio values for obstruction.

Answer:

FEV₁/FVC ratio is less than 75%