Flow-volume curves: Severe expiratory airway obstruction
Immediately
after the peak expiratory flow, the flow drops to low values until
the end of the forced expiration. This pattern is compatible with
severe airflow limitation. Expiratory flow during normal tidal breathing
is at the same level as during a forced expiration; this signifies
the presence of a flow limiting segment during normal respiration,
so that each normal expiration is in fact a forced expiration at
the expense of considerable work of breathing. The ventilatory reserves
in this patient are therefore minimal. During physical exercise
inspiratory flow can be relatively easily increased, unlike expiratory
flow; therefore end-expiratory volume will increase sharply, exacerbating
the hyperinflation in this patient.
This pattern is encountered in the case of loss of elastic lung recoil associated with dynamic compression of intrathoracic airways, such as occurs in pulmonary emphysema.
See also:
Added value of tidal flow-volume
curve
After bronchodilatation