Final answer:
Pregnancy induces physiological changes in the respiratory system, evident in Pulmonary Function Tests (PFT), such as increased respiratory minute volume and alterations in volume capacities. The upward displacement of the diaphragm by the growing uterus reduces breath volume, potentially causing dyspnea, which may diminish with the lightening process at the end of pregnancy.
Step-by-step explanation:
During pregnancy, certain physiological changes occur in the respiratory system, which can be observed in Pulmonary Function Tests (PFT). Increased oxygen demands of the fetus and the mother's metabolism result in a 50% rise in the respiratory minute volume. This escalation is a consequence of augmented tidal volume and slightly increased respiratory rate. The growing uterus causes an upward shift of the diaphragm, which decreases the volume of each breath and leads to sensations of shortness of breath or dyspnea. However, near the end of pregnancy, after lightening takes place—when the fetus descends lower in the pelvis—there can be a reduction in dyspnea.
Comprehending these alterations is critical for interpreting PFT results properly during pregnancy. Some key measurements affected include a reduction in residual volume (RV) and functional residual capacity (FRC), typically due to the diaphragmatic elevation. However, volume like forced vital capacity (FVC) remains relatively stable. On the other hand, increases in tidal volume can enhance peak expiratory flow (PEF), which is a consequence of hormonal softening of the airways.
It is important to note these changes when evaluating PFTs in pregnant patients, as they can mimic or obscure pathological conditions.