Dr Henry Jefferson, Consultant Anaesthetist
#QuestionFeedback 10. Lung Capacities A useful terminology clarification. Although FRC describes a volume of gas within the lungs, it is formally classified as a lung CAPACITY because it consists of two volumes: FRC = ERV + RV Closing capacity (CC) is similarly composed of closing volume + residual volume. When CC approaches or exceeds FRC, small airway closure can occur during normal tidal breathing. This becomes particularly relevant under general anaesthesia, when FRC commonly decreases.