Why is the functional residual capacity (FRC) reduced in a pregnant patient?

The reduction of functional residual capacity (FRC) in a pregnant patient primarily occurs due to the lifting of the diaphragm by the gravid uterus. As the uterus expands, particularly during the later stages of pregnancy, it exerts upward pressure on the diaphragm. This displacement decreases the space available for lung expansion and reduces the FRC, which is the volume of air remaining in the lungs after a normal exhalation.

This anatomical change is crucial because a reduced FRC can influence the patient's respiratory physiology and may have implications for oxygenation and overall respiratory function during labor and delivery. Understanding these physiological adaptations is important for ensuring appropriate monitoring and management of pregnant patients in critical care settings.