In obstructive lung disease, which pulmonary function test results are expected?

In obstructive lung disease, the hallmark pulmonary function test results include a decreased forced expiratory volume in one second (FEV1) and a reduced FEV1/FVC ratio, with a relatively preserved or even increased total lung capacity (TLC) and residual volume (RV). This pattern arises from airflow limitation that characterizes obstructive conditions such as asthma, chronic bronchitis, or emphysema.

The increase in total lung capacity and residual volume occurs because patients with obstructive lung disease often cannot exhale fully, leading to air trapping. Therefore, while FEV1 is decreased, the vital capacity (VC) is typically also reduced but could be perceived as increased in cases of hyperinflation. However, it is important to note that in obstructive diseases generally, vital capacity is not increased compared to normal but can reflect variable outcomes based on individual pulmonary mechanics.

Thus, the correct choice indicates that all pulmonary function values except vital capacity show an increase, consistent with the pathophysiological characteristics of obstructive lung disease. This understanding helps in distinguishing between obstructive and restrictive lung patterns, clarifying the effects of these conditions on lung function testing.