Wallach's Interpretation of Diagnostic Tests: Pathways to Arriving at a Clinical Diagnosis (588 page)

   
Stage III
—severe: with or without chronic symptoms (cough, sputum production); further worsening of airflow limitation (FEV
₁
/FVC <70%; 30% < FEV
₁
< 50% predicted).

   
Stage IV
—very severe: with or without chronic symptoms (cough, sputum production); severe airflow limitation (FEV
₁
/FVC <70%; FEV
₁
<30% predicted); or FEV
₁
<50% predicted plus chronic respiratory failure. Patients may have very severe (stage IV) COPD even if the FEV
₁
is >30% predicted, whenever this complication is present.

   Who Should Be Suspected?

The dominant symptoms of COPD are coughing and shortness of breath on activity, but some patients present with acute breathlessness and wheezing, which is difficult to distinguish from asthma. There are three typical ways that patients with COPD present. Some patients have few complaints but an extremely sedentary life style. Other patients describe chronic respiratory symptoms (e.g., dyspnea on exertion, cough). Finally, some patients present with an acute exacerbation (e.g., wheezing, cough, and dyspnea). The physical examination of chest varies with severity of COPD.

   COPD should be considered and PFTs performed in all patients who report any combination of the following: chronic cough, chronic sputum production, dyspnea or inhalational exposure to tobacco smoke, occupational dust, or occupational chemicals. COPD is confirmed when a patient who has symptoms that are compatible with COPD is found to have airflow obstruction (FEV
₁
/FVC <0.70), and there is no alternative explanation for the symptoms and airflow obstruction.

   Diagnostic Findings

   Spirometry: This is an essential test to confirm the diagnosis and establish the staging of COPD. If values are abnormal, a post–bronchodilator test may be indicated. Reversibility following bronchodilator would suggest asthma, and, if function reversed to normal, would exclude COPD. The FVC or FEV is needed to establish the presence of obstruction (see above for significance of specific values). The inspiratory capacity may decrease acutely with tachypnea due to dynamic hyperinflation. It is the best physiologic correlate of dyspnea, but it is not usually required to diagnose COPD.

   Carbon monoxide (CO) diffusing capacity: Measurement of CO diffusing capacity can help establish the presence of emphysema, but it is not necessary for the routine diagnosis of COPD.

   Chest radiography: Only diagnostic of severe emphysema but always essential to exclude other lung diseases.

   Blood gas: ABGs are not needed in mild (FEV
₁
>80%) and moderate (FEV
₁
65–79%) airflow obstruction. ABGs are optional except oximetry, which should be measured in moderately severe (FEV
₁
50–64%) airflow obstruction. (ABGs should be measured if oxygen saturation is >88%.) ABGs should be monitored in all severe (FEV
₁
30–49%) and very severe (FEV
₁
<30%) airflow obstruction.

   Alpha-1-antitrypsin deficiency can cause COPD (inherited emphysema).

Suggested Reading

Documents and Resources. Global Initiative for Chronic Obstructive Lung Disease (
http://www.goldcopd.org
).

CYSTIC FIBROSIS
*

   Definition