To show influence of forced maneuver condition on results of the examination, the instructor can manipulate the following factors:
- deepness of expiration,
- rapidity of expiration (the rate of the effort increase),
- deepness of inspiration,
- the criterion of the expiration end (according to the present recommendations of ATS/ERS, the expiration should terminate not before the airflow is smaller than 25 mL/sec).
To explain the forced expiratory maneuver physiologically, the instructor can show how the following variables change during the expiration:
- total airflow,
- airflow from/to lungs — (the air that flows from/to lungs),
- airflow presented only when flow limitation exists,
- resistance of intermediate bronchi,
- resistance of peripheral bronchi,
- intrathoracic pressure.
The instructor can change selectively properties of lobes to simulate asymmetrical lungs disease.