Final answer:
Pregnancy induces significant changes in the maternal respiratory system, including an increase in respiratory minute volume to compensate for the oxygen demands of the fetus and a shift in blood chemistry markers like PaCO₂ and HCO₃₋. Physical changes such as the expanding uterus can lead to shortness of breath, which generally improves near the end of pregnancy.
Step-by-step explanation:
During pregnancy, especially in the second half, several physiological changes occur in the maternal respiratory system. One significant change is a 50 percent increase in the respiratory minute volume (MV), which is the volume of gas inhaled or exhaled by the lungs per minute. This increase helps to meet the heightened oxygen demands of the fetus and supports the mother's increased metabolic rate. The uterus grows and exerts upward pressure on the diaphragm, potentially leading to shortness of breath or dyspnea. However, dyspnea often improves towards the end of pregnancy when the fetus descends lower in the pelvis, a process known as lightening.
Respiratory adaptations also include changes in blood chemistry, where levels of PaCO₂ decrease and pH might show compensatory changes to maintain homeostasis. This is reflected in lab tests measuring blood pH, CO₂ partial pressure, and bicarbonate levels (HCO₃₋). Understanding these changes is crucial for ensuring maternal and fetal well-being and for guiding medical care.