flow-volume loop

Indications

• upper airway obstruction
• chronic obstructive lung disease
• reactive airway disease, i.e. asthma

Clinical significance

Characteristic patterns occur for certain respiratory disorders:

• a plateau during forced inspiration is characteristic of extrathoracic upper airway obstruction (paradoxical vocal cord motion)
• a plateau during forced expiration is characteristic of intrathoracic upper airway obstruction (tumor compressing trachea)
• a plateau during both forced inspiration & expiration is characteristic of a fixed upper airway obstruction such as tracheal stenosis
• low flow rates with minimal change with bronchodilation occur with chronic obstructive lung disease
• low flow rates that improve with bronchodilation characterize reactive airway disease, i.e. asthma

Procedure

• graphic displays of lung volume & airflow.

More general terms

• pulmonary function test (PFT)
• loop