Chronic obstructive pulmonary disease other diagnostic studies

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Philip Marcus, M.D., M.P.H. [2]; Associate Editor(s)-In-Chief: Cafer Zorkun, M.D., Ph.D. [3]

Overview

The diagnosis of COPD is confirmed by spirometry, a test that measures the forced expiratory volume in one second (FEV₁), which is the greatest volume of air that can be breathed out in the first second of a large breath. Spirometry also measures the forced vital capacity (FVC), which is the greatest volume of air that can be breathed out in a whole large breath. Normally, at least 70% of the FVC comes out in the first second (i.e. the FEV₁/FVC ratio is >70%). A ratio less than normal defines the patient as having COPD.

File:COPD.JPG

A chest X-ray demonstrating severe COPD. Note the small size of the heart in comparison to the lungs.

Spirometry

• COPD is particularly characterized if a ratio of forced expiratory volume over 1 second (FEV₁) to forced vital capacity (FVC) being < 0.7 and the FEV₁ < 70% of the predicted value when compared with a matched control. , (see Spirometry).
• Normally, at least 70% of the FVC comes out in the first second (i.e. the FEV₁/FVC ratio is >70%). A ratio less than normal defines the patient as having COPD.
• More specifically, the diagnosis of COPD is made when the FEV₁/FVC ratio is <70%.
• The GOLD criteria also require that values are after bronchodilator medication has been given to make the diagnosis,
• The NICE criteria also require FEV1%.
• According to the ERS criteria, it is FEV1% predicted that defines when a patient has COPD, that is, when FEV1% predicted is < 88% for men, or < 89% for women.
• Spirometry can help to determine the severity of COPD.
• The FEV₁ (measured after bronchodilator medication) is expressed as a percentage of a predicted "normal" value based on a person's age, gender, height and weight:
• The severity of COPD also depends on the severity of dyspnea and exercise limitation. These and other factors can be combined with spirometry results to obtain a COPD severity score that takes multiple dimensions of the disease into account.

The severity of COPD can be classified as follows using spirometry

Severity	FEV1 /FVC	FEV1 % predicted
At risk	>0.7	≥80
Mild COPD	≤0.7	≥80
Moderate COPD	≤0.7	50-80
Severe COPD	≤0.7	30-50
Very Severe COPD	≤0.7	<30 or 30-50 with Chronic Respiratory Failure symptoms

References

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