A 56-year-old female shows increased lung capacity and decreased FEV1. What is the likely diagnosis?

The scenario describes a 56-year-old female with increased lung capacity and decreased FEV1, which aligns with the characteristics of chronic obstructive pulmonary disease (COPD). In COPD, particularly emphysema, there is destruction of lung parenchyma leading to air trapping and increased lung volumes, such as total lung capacity (TLC) or residual volume (RV).

The decreased FEV1 indicates that the patient is experiencing obstruction in airflow, which is a hallmark of COPD. The FEV1/FVC ratio is often used to distinguish obstructive from restrictive lung disease; in the case of COPD, this ratio is typically less than 70%, further supporting that the lung obstruction is significantly impacting the patient's ability to exhale forcefully.

On the other hand, conditions like persistent asthma can also show similar findings but typically involve variable obstruction that can improve with bronchodilators. Idiopathic fibrosing interstitial pneumonia and sarcoidosis are more associated with restrictive lung patterns, leading to decreased lung capacity rather than an increase, as well as a lower FEV1. Therefore, based on the presented symptoms of increased lung capacity alongside decreased FEV1, the most likely diagnosis is chronic obstructive pulmonary disease.