Which of the following is not true in obstructive lung disease?
**Core Concept**
Obstructive lung disease is characterized by airway obstruction, resulting from conditions such as chronic obstructive pulmonary disease (COPD) and asthma. This leads to increased resistance to airflow, making it difficult for patients to exhale fully.
**Why the Correct Answer is Right**
In obstructive lung disease, the total lung capacity (TLC) is typically normal or increased due to air trapping. This occurs because the airways are narrowed, causing air to become trapped in the lungs, leading to hyperinflation of the lungs. However, the functional residual capacity (FRC) is increased, and the residual volume (RV) is also increased. The TLC is not decreased in obstructive lung disease; in fact, it is often normal or elevated due to air trapping.
**Why Each Wrong Option is Incorrect**
**Option A:** FEV1 (forced expiratory volume in one second) is typically decreased in obstructive lung disease due to airway obstruction, making this statement true, not false.
**Option C:** FVC (forced vital capacity) is often decreased in obstructive lung disease due to airway obstruction, making this statement true, not false.
**Option D:** Reduced timed vital capacity is a characteristic feature of obstructive lung disease, making this statement true, not false.
**Clinical Pearl / High-Yield Fact**
In obstructive lung disease, the ratio of FEV1 to FVC is decreased, and the TLC is often normal or increased due to air trapping.
**✓ Correct Answer: B. TLC| TLC is typically normal or increased in obstructive lung disease.**