In restrictive lung disease, TLC is -

Ans. is 'b' i.e., Decreased o Lung volumes alter in many lung diseases as follows : -1) Chronic obstructive lung diseases (COPD):# Dynamic compression of airways occurs mainly in expiration (Dynamic compression of airways will be discussed later in details).# So, air tends to enter the lung easily (as inspiraton is less affected) but then becomes trapped in the lung over a period of months or year, this increases total lung capacity, residual volume (RV) and functional residual capacity (FRC). Due to obstruction FEV1 is decreased and vital capacity is also decreased later.# The characteristic feature of COPD is early decrease of FEV1 and out of proportion to vital capacity/forced vital capacity. Therefore, FEV1/FVC is decreased.# The most important COPD is emphysema.2) Restrictive lung disease :# Restrictive lung diseases are characterized by decreased lung compliance and constricted lungs.# Therefore, all volumes and capacity are decreased. TLC, FEV1, VC/FVC, RV, FRC all are reduced.# FEV1 is decreased in proportion or slightly less than FRV; therefore, FEV1/FVC is either normal or slightly increased.# Interstitial lung diseases (like pneumoconiosis, interstitial pneumonitis, sarcoidosis) and pulmonary fibrosis are restrictive lung diseases.