Flow Volume Loop Spirometry 

Why?

The flow volume loop is a graph showing the airflow at different lung volumes, and plots inspiratory and expiratory function separately. It enables a clear diagnosis to be made between fixed and variable upper and lower airway obstruction, and gives quantitative data for assessment and monitoring purposes. It is particularly helpful in measuring the degree of airway obstruction in patients with vocal cord paralysis.

How?

The subject is asked to breathe out completely to empty air from the lungs as much as possible. The airflow at the mouth is then recorded during a maximum forced inspiration, followed by a maximum forced expiration. The results undergo computer  analysis and are recorded.