[1] Pulmonary function testing has diagnostic and therapeutic roles and helps clinicians answer some general questions about patients with lung disease.

Pulmonary function testing is a diagnostic and management tool used for a variety of reasons, such as: Pulmonary function testing in patients with neuromuscular disorders helps to evaluate the respiratory status of patients at the time of diagnosis, monitor their progress and course, evaluate them for possible surgery, and gives an overall idea of the prognosis.

[4] Spirometry includes tests of pulmonary mechanics – measurements of FVC, FEV1, FEF values, forced inspiratory flow rates (FIFs), and MVV.

Physicians may also use the test results to diagnose bronchial hyperresponsiveness to exercise, cold air, or pharmaceutical agents.

[5] The helium dilution technique for measuring lung volumes uses a closed, rebreathing circuit.

Measurement of maximal inspiratory and expiratory pressures is indicated whenever there is an unexplained decrease in vital capacity or respiratory muscle weakness is suspected clinically.

[citation needed] Measurement of the single-breath diffusing capacity for carbon monoxide (DLCO) is a fast and safe tool in the evaluation of both restrictive and obstructive lung disease.

[citation needed] When a patient has an obstructive defect, a bronchodilator test is given to evaluate if airway constriction is reversible with a short acting beta-agonist.

[9] The six-minute walk test is a good index of physical function and therapeutic response in patients with a chronic lung disease, such as COPD or idiopathic pulmonary fibrosis.

[10][11][12] Arterial blood gases (ABGs) are a helpful measurement in pulmonary function testing in selected patients.

The primary role of measuring ABGs in individuals that are healthy and stable is to confirm hypoventilation when it is suspected on the basis of medical history, such as respiratory muscle weakness or advanced COPD.

[citation needed] ABGs also provide a more detailed assessment of the severity of hypoxemia in patients who have low normal oxyhemoglobin saturation.

Some complications include dizziness, shortness of breath, coughing, pneumothorax, and inducing an asthma attack.

The interpretation of tests depends on comparing the patients values to published normals from previous studies.

[19] The Global Initiative for Chronic Obstructive Lung Disease provides guidelines for the diagnosis, severity, and management of COPD.

[18] Several calculations are needed for what a normal maximum inspiratory (MIP) and expiratory pressure (MEP) is.