Which lung volume changes the least during pregnancy?

Which lung volume changes the least during pregnancy?

• A. Tidal Volume
• B. Functional Residual Capacity
• C. Expiratory Reserve Volume
• D. Residual Volume

Answer: (D)

During pregnancy the respiratory system adapts to meet higher oxygen needs, mainly by increasing tidal volume as the diaphragm is pushed upward by the enlarging uterus. This diaphragmatic shift shortens the expiratory reserve and lowers the functional residual capacity, while ventilation increases to maintain gas exchange. Residual volume, the air left after a maximal exhale, is relatively insensitive to this diaphragmatic elevation and the associated chest wall changes, so it changes the least compared with the other volumes. In short, tidal volume rises, FRC and expiratory reserve decrease, and residual volume stays the most stable.

During pregnancy the respiratory system adapts to meet higher oxygen needs, mainly by increasing tidal volume as the diaphragm is pushed upward by the enlarging uterus. This diaphragmatic shift shortens the expiratory reserve and lowers the functional residual capacity, while ventilation increases to maintain gas exchange. Residual volume, the air left after a maximal exhale, is relatively insensitive to this diaphragmatic elevation and the associated chest wall changes, so it changes the least compared with the other volumes. In short, tidal volume rises, FRC and expiratory reserve decrease, and residual volume stays the most stable.