A patient with obstructive airway disease will show a number of changes in the breath flow-volume (F-V) loop.
A patient with airway obstruction may show:
(1) a decrease in the height of the expiratory portion of the curve with a depressed peak expiratory flow rate (PEFR)
(2) a curvilinear shape ("scooping") of the descending segment of the expiratory curve
If air trapping occurs (due to premature collapse of smaller airways or insufficient time for expiration), then the expiratory flow does not reach zero before the start of the next inspiration.
If the airway obstruction is reversible then appropriate therapy should reverse these changes, normalizing the loop.
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