Functional residual capacity

Functional residual capacity (FRC): The amount of air remaining in the lungs after a calm exhalation. FRC = RC + ERV. FRC physiologically plays a buffering role in stabilizing the alveolar gas partial pressure, reducing the effect on the gas exchange in the alveoli during the interval of ventilation. Without FRC, the end-expiratory alveoli will be completely closed. An increase in FRC indicates alveolar dilation, and a decrease in FRC indicates alveolar contraction or occlusion.

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