Which of the following is NOT a finding associated with obstructive lung disease?

In obstructive lung diseases, such as asthma and chronic obstructive pulmonary disease (COPD), the hallmark diagnostic feature is the limitation of airflow due to partial or complete obstruction. As such, one of the primary findings in these conditions is a decreased FEV1/FVC (Forced Expiratory Volume in 1 second/Forced Vital Capacity) ratio, indicating that the reduction in airflow is greater than the reduction in lung volume capacity.

The total lung capacity (TLC) typically remains normal or may even be increased in obstructive lung diseases due to air trapping. As a result, the option indicating decreased total lung capacity is not consistent with the pathophysiology of obstructive lung diseases.

On the other hand, an increased residual volume (RV) is common because individuals with obstructive lung diseases often experience air trapping, leading to an increase in the amount of air left in the lungs after exhalation. The FEV1 will usually be decreased due to the obstruction, while the FEV1/FVC ratio will also decrease, supporting the diagnosis of an obstructive pattern. Thus, the finding associated with decreased total lung capacity stands out as incorrect in the context of obstructive lung disease.