What are common respiratory system changes during pregnancy?

Pregnant women experience nasal stuffiness due to estrogen-induced hypersecretion of mucus. Epistaxis is also common. The safest treatment of these symptoms is a saline nasal spray. The following is a summary of respiratory changes:

• Respiratory rate does not change.
• Tidal volume increases 0.1-0.2 L.
• Expiratory reserve volume (ERV) decreases 15%.
• Residual volume decreases.
• Vital capacity does not change.
• Inspiratory capacity increases 5%.
• Functional reserve capacity decreases 18%.
• Minute volume increases 40%.

Source: http://emedicine.medscape.com/