The defining feature of COPD is irreversible airflow limitation during forced expiration. This may result from a loss of elastic recoil due to lung tissue destruction or from an increase in the resistance of the conducting airways. The formal diagnosis of COPD is made with spirometry; when the FEV1/FVC ratio is less than 70% of that predicted for a matched control, it is diagnostic for a significant obstructive defect.
Pulmonary function tests are essential for the diagnosis and assessment of the severity of disease, and they are helpful in following its progress. FEV1 is a reproducible test and is the most commonly used index of airflow obstruction. In addition to the spirometry findings that define the disease, lung volume measurements often show an increase in total lung capacity, functional residual capacity, and residual volume. The vital capacity often decreases. Dynamic hyperinflation during exercise is now thought be a greater contributor to the sensation of dyspnea than airflow obstruction alone (as measured by FEV1).
Other studies, including laboratory studies and imaging, are particularly important during acute exacerbations of disease. No blood-based biomarkers are accepted in COPD. High-resolution CT is more sensitive than standard chest radiography and is highly specific for diagnosing emphysema (outlined bullae are not always visible on a radiograph).
Pulse oximetry does not offer as much information as arterial blood gas analysis. However, when combined with clinical observation, this test can be a powerful tool for instant feedback on a patient's status.
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Cite this: Zab Mosenifar. Fast Five Quiz: COPD Key Aspects - Medscape - Aug 10, 2020.