In a pregnant patient, which pulmonary function tests are typically altered?

In pregnant patients, there are significant physiological changes that affect pulmonary function tests due to the growing uterus and hormonal influences. One of the primary alterations observed is a decrease in functional residual capacity (FRC), which is the volume of air remaining in the lungs after a normal expiration. This reduction occurs primarily due to the upward displacement of the diaphragm, resulting from the enlarging uterus.

Additionally, during pregnancy, there is an increase in tidal volume, which is the amount of air inhaled or exhaled during normal breathing. This increase in tidal volume helps to meet the increased oxygen demands of both the mother and the developing fetus.

As for vital capacity (VC), which includes both the inspiratory and expiratory reserve volumes along with tidal volume, the forced vital capacity (FVC) might decrease slightly due to the mechanical changes in the thoracic cavity. However, the total lung capacity (TLC) shows relatively modest changes overall, while the FVC might not decrease as markedly as FRC.

Thus, the option indicating decreased FRC, increased tidal volume, and decreased FVC accurately describes the expected alterations in pulmonary function tests during pregnancy, reflecting the complex interplay of anatomical, physiological, and hormonal changes occurring in the mother’s body.