Total lung capacity depends upon
TLC = (IRV + TV + ERV + RV) When a person inspires maximally, the lungs are at TLC. This total volume of inspired air (3000 + 500) would depend on the distensibility of the lungs. Greater the compliance, more is the distensibility and greater the amount that can be inspired. Conversely, if the compliance is reduced (as in fibrosis), the lungs cannot be distended to a great extent and TLC will be less. TLC is greater in emphysema,Due to incomplete expiration and air trapping beyond compressed airways, residual volume is increased. It may contribute to increase in TLC. However, TLC does not depend on residual volume
Size of airway
Closing volume
Residual volume
Lung compliance
Respiratory System Pa 1