What characteristic pulmonary function change might be observed in COPD?

In chronic obstructive pulmonary disease (COPD), one of the hallmark characteristics seen in pulmonary function tests is a decreased forced expiratory volume in one second (FEV1) and a reduced FEV1/FVC ratio. This reduction occurs due to the airflow obstruction that is typical of COPD, resulting from the combination of chronic bronchitis and emphysema, both of which impede airflow.

In a normal individual, the FEV1/FVC ratio is typically above 0.70, indicating that a relatively large proportion of the total volume of air can be expelled in the first second of forced expiration. In patients with COPD, the obstruction results in a significant decline in the FEV1 value while the FVC (forced vital capacity) might be less affected, leading to a lowered FEV1/FVC ratio, confirming the presence of an obstructive pattern.

This pattern helps differentiate COPD from other respiratory conditions, such as restrictive lung diseases, where FEV1 and FVC would both be reduced, but the FEV1/FVC ratio might remain normal or even increase. Therefore, observing both decreased FEV1 and FEV1/FVC ratio is crucial in diagnosing and understanding the severity and implications of COPD.