Human lung volumes and the mechanisms that set them

Definitions of human lung volumes and the mechanisms that set them are revi ewed in the context of pulmonary function testing, with attention to the di stinction between functional residual capacity (FRC) and the static relaxat ion volume of the respiratory system, and to the circumstances in which FRC and residual volume are set by dynamic rather than by static mechanisms. R elated terms, conventions, and issues are addressed, including some common semantic and conceptual difficulties, with attention to "gas trapping", "hy perinflation",and "restriction".