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. Six minute walk tests act as an predictor of mortality in patients with moderate COPD (patients who desaturate have worse mortality compared with those who don't desaturate.)

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

Six minute walking distance

• It act as a good predictor of mortality in patients with COPD.
• Patients who desaturate during 6MWD have higher mortality compared to those who doesn't desaturate.
• This test is a part of BODE index which is used as a mortality predictor for patients with COPD.
• The BODE index has the following component
  • Body mass index
  • Obstruction (FEV1)
  • Dyspnea (MMRC dyspnea scale)
  • 6 minute walking distance.

References

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