Interpretation of Pulmonary Function Tests: Spirometry
Thomas Gross, M.D.
Associate Professor
Department of Internal Medicine
Division of Pulmonary, Critical Care, and Occupational Medicine
The University of Iowa
Physician CME Sponsored by:
The Department of Internal Medicine
University of Iowa Carver College of Medicine
Peer Review Status: Externally Peer Reviewed
First Published: October 1996
Last Revised: June 2002
Introduction
Pulmonary function testing is one of the basic tools for evaluating a patient's respiratory status. In patients with suspected pulmonary disease, it is often the first diagnostic test employed in the work up. Pulmonary function tests (PFT's) are also used for pre-operative evaluation, managing patients with known pulmonary disease, and quantifying pulmonary disability. Although the fully equipped PFT laboratory utilizes a host of sophisticated equipment, simple spirometry is relatively easy to administer and standardize and has become portable enough to use at outreach clinics and industrial health centers. The increasing availability of spirometry has led to greater use by both primary care physicians and specialists, some of whom may lack formal training in interpreting results. This educational module is designed to provide an introduction to quality assessment and basic interpretation of spirometric testing.
The Global Initiative for Chronic Obstructive Lung Disease (GOLD) has proposed a classification scheme based upon spirometry that is easily adapted from this interpretation format. This group defines smokers at risk for COPD (GOLD Stage 0) as having chronic symptoms of cough and sputum production with normal spirometry. Stage I, or Mild COPD, is defined as obstructive physiology (FEV1/FVC < 70%) with a preserved FEV1 (>80% predicted) independent of the presence of symptoms. Similarly, GOLD Class II (Moderate) is defined as FEV1 between 50% and 80%, Class III (Severe) as FEV1 between 30% and 50% , and Class IV (Very Severe) as FEV1 <30% of normal predicted values. A management and treatment schema developed around this classification system is presently under evaluation (http://www.goldcopd.com).