True about obstructive lung disease is –
**Core Concept**
Obstructive lung disease refers to a group of respiratory conditions characterized by airflow limitation due to obstruction of the airways. This type of disease is primarily associated with conditions such as chronic obstructive pulmonary disease (COPD), asthma, and bronchiectasis.
**Why the Correct Answer is Right**
Obstructive lung disease involves the narrowing of the airways, which leads to increased resistance to airflow. This is primarily due to inflammation, bronchospasm, and excess mucus production, which cause the airway diameter to decrease. The increased resistance to airflow in obstructive lung disease can be demonstrated by a decrease in the forced expiratory volume in one second (FEV1) and a decrease in the forced vital capacity (FVC) ratio (FEV1/FVC).
**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because obstructive lung disease is not primarily characterized by a decrease in lung compliance, which is more commonly associated with restrictive lung diseases.
**Option B:** This option is incorrect because obstructive lung disease involves an increase in airway resistance rather than a decrease, which would be more characteristic of a restrictive lung disease.
**Option C:** This option is incorrect because the hallmark of obstructive lung disease is not an increase in lung volume, but rather an increase in residual volume (RV) and total lung capacity (TLC).
**Clinical Pearl / High-Yield Fact**
A key clinical feature of obstructive lung disease is the characteristic "fixed" or "reversible" airflow limitation, as demonstrated by spirometry. In COPD, airflow limitation is typically irreversible, while in asthma, it is often reversible with treatment.
**Correct Answer: D**