Question

During which postoperative period is functional residual capacity (FRC) classically the lowest, and what factors contribute to this reduction in lung volume?

Answer 1

The functional residual capacity (FRC) is the lowest in the immediate postoperative period due to factors like diminished respiratory muscle tone, pain, anesthesia effects, and reduced recruitment of airways. Lung conditions like fibrosis can also contribute to the decrease in FRC.

Step-by-step explanation:

Reduction of Functional Residual Capacity After Surgery

After surgery, the period during which the functional residual capacity (FRC) is classically the lowest is the immediate postoperative period. The FRC is defined as the sum of expiratory reserve volume (ERV) and residual volume (RV), which is the amount of air that remains in the lungs after a normal exhalation. Reduction in FRC typically occurs due to factors such as decreased respiratory muscle tone, pain that inhibits deep breathing, and effects of anesthesia. Additionally, patients may experience a reduction in the recruitment process of airways, which can further decrease FRC. The presence of lung conditions, such as fibrosis, can also contribute to a reduction in lung volumes, affecting FRC and other measurements such as total lung capacity (TLC) and slow vital capacity (SVC).