How does the gravid uterus affect functional residual capacity (FRC) in pregnant patients?

During pregnancy, the enlarging uterus significantly influences the respiratory system, particularly the functional residual capacity (FRC). The functional residual capacity is the volume of air present in the lungs after a normal exhalation, which allows for adequate gas exchange between breaths.

As the gravid uterus expands, it exerts upward pressure on the diaphragm, which reduces the vertical dimension of the thoracic cavity. This mechanical restriction limits the expansion of the lungs, thereby leading to a decrease in FRC. The reduced space for lung inflation causes the lungs to have less reserve volume available, which can impact ventilation and, consequently, oxygenation.

Understanding this physiological change is crucial for the management and care of pregnant patients, especially in critical care settings where respiratory function can be impacted significantly. The decreased FRC can predispose these patients to complications such as hypoxemia, making awareness and monitoring essential in clinical practice.