Question

Explain how spirometry test results can be used to diagnose respiratory diseases or determine the effectiveness of disease treatment.

Answer 1

Spirometry is used to diagnose asthma, chronic obstructive pulmonary disease (COPD) and other conditions that affect breathing. Flow volumes curves are helpful in the detection of large airway abnormalities. Typically intra-thoracic large airway obstruction (e.g. from a lower tracheal or bronchial tumour results in flattening of the expiratory limb alone with preservation of the inspiratory limb. Normally in expiration there is a rise in intrathoracic pressure, which is transmitted to the intrathoracic airway causing some narrowing of the airway. The presence of an obstructing lesion coupled with a rise in intrathoracic pressure during expiration results in a more pronounced and pathological reduction in airflow through the obstructed or partially occluded intrathoracic airway.