njit-etd2003-081 - New Jersey Institute of Technology

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2.7.1 Classification of COPD by Severity
When classifying COPD severity in clinical settings, physicians rely on the results
obtained from standardized spirometry. When performing spirometry, one measures:
1. Forced Vital Capacity (FVC) and
2. Forced Expiratory Volume in one second (FEV1).
3. The FEV1/FVC ratio is then calculated.
Spirometric results are expressed as % predicted using appropriate normal
values for the person's sex, age, and height. Patients with COPD typically show a
decrease in both FEV1 and FEV1/FVC. A postbronchodilator spirometric measurement
of forced expiratory volume in one second (FEV1) less than 80% predicted and a ratio of
FEV1 to forced vital capacity (FEV1/ FVC) below 70% suggest airflow limitation that is
not fully reversible and according to Rennard: "A decreased ratio is considered an early
sign of COPD, even if the FEV1 is normal." [7]
COPD is classified from stage 0 to stage III (Table 2.3) according to the
guideline of the Global Initiative for Chronic Obstructive Lung Disease Committee
(GOLD) as follow:
Stage 0: At Risk - Chronic cough and sputum production; lung function is still normal.
Stage I: Mild COPD - Mild airflow limitation (FEV1/FVC < 70% but FEV1 > or equal
to 80 % predicted) and usually, but not always, chronic cough and sputum production.
• At this stage, the individual may not be aware that his or her lung function is
abnormal.