Figure 1

Relationship of volume and pressure in the respiratory system. Dynamic hyperinflation adds an elastic load to inspiratory muscles: to initiate inspiratory flow the inspiratory muscles must first overcomeintrinsic positive end-expiratory pressure (PEEP_I). Dynamic hyperinflation shifts tidal breathing to a less compliant part of the respiratory system pressure-volume curve leading to an increased pressure-volume work of breathing. FRC, functional residual capacity.