Cough
This
subject coughed during the forced expiration. Typically the glottis
is nearly closed (flow drops to slightly above 0), removing the
flow-limiting segment from the intrathoracic airways. The glottis
is subsequently opened rapidly, giving rise to a new peak flow and
re-establishment of a flow-limiting segment.
Neither the FVC nor the FEV1 can be reliably measured during cough, so that recorded data should
not be interpreted. The fact that the maneuver induces coughing
is medically relevant: in healthy subjects this is rare, but it
is often observed in subjects with hyperreactive airways.
See also:
Flow-volume curve without cough