🔸In the pregnant patient, the respiratory function deviates from the normal

🔸There is increased CO2 production by the mother and the foetus; but mostly you see a respiratory alkalosis. Why?
🔸This is because the stimuli from the raised pCO2 levels and that by the respiratory stimulant, progesterone, sets the minute ventilation approximately 30% higher than the normal levels and this is more than what is needed to compensate for the increased CO2 production 
🔸It is mainly the reduction in FRC (a reduction by 10-25% ; appears by 12th week ; is due to the reduced chest wall compliance ; lung compliance is normal ) which makes the patient more vulnerable to hypoxia.
🔸The alveolar diffusing capacity is reported to be normal during pregnancy