Pulmonary function tests are usually ordered when patients go to their primary physician or a pulmonary specialist with complaints of shortness of breath, cough, decreased activity, and dyspnea. When the history is taken, patients’ complaints are due to their breathing problem, for example they are short of breath walking up stairs or dressing. As dyspnea begins to affect their daily life more and more, people will often make lifestyle changes, such as selling a two-story house and moving to a ranch house with no stairs or altering the way they dress (e.g., wearing housecoats or jogging pants that are easier to put on and take off). Often, people think that their breathing problems are just part of getting older, and they try to change their lifestyle to accommodate their limitations and avoid doing things that make them short of breath. In many cases, by the time a patient comes to the care provider with these complaints, he or she is already showing signs of moderate to severe chronic obstructive pulmonary disease (COPD). As will be discussed in this chapter, this is a very good reason for considering office spirometry to be a “fifth vital sign.” Suggestions have been made that all smokers and any nonsmoker over 40 years of age should have office spirometry. If the values are abnormal, even though patients may not be experiencing noticeable lifestyle changes, the appropriate drug therapy regimen can be implemented and patients who are smokers will have a definite motivation to quit smoking.

Pulmonary function tests (PFTs) help in the evaluation of the mechanical function of the lungs.¹ They are based on researched norms, taking into account sex, height, and age. For example, there are predicted values for a male, age 65, who is 6 feet tall.^2,3 Race and ethnic differences also play roles in the reference values and need to be taken into account for diagnostic and research purposes.^4–6

When the patient performs the test, actual results (observed) are compared with the predicted value expected of a person of that gender, height, and age to see whether he or she falls within the “normal” range or has a restrictive, obstructive, or a mixed component, based on the tests. If the patient is not within the normal range, a bronchodilator is given, and the test is repeated to see whether there is significant improvement with medication. Basically, the pulmonary function tests are categorized as volume, flow, or diffusion studies. Diagnosis of pulmonary disease or dysfunction and improvement with treatment are evaluated after interpreting a patient’s pulmonary function tests.

Spirometry is the most useful and commonly available test of pulmonary function. Both pulmonologists and primary care physicians commonly use screening spirometry in their offices in order to assess patients and to evaluate the effectiveness of treatment being given to the patient.⁷

Patients with asthma and COPD make up a large portion of the primary care physician’s caseload. COPD is often diagnosed in the moderate to severe stage of the disease. The diagnosis of COPD can be made quite easily with spirometry, taking the patient’s symptoms and history into account. Smokers can be evaluated for early lung disease, and this can serve as a “teachable moment” for them to quit smoking.⁸

Yawn and colleagues (2007)⁹ compared the office spirometry interpretations of pulmonary experts with those of family physicians. They found agreement in 78% of the completed tests. In addition, following spirometry, changes were implemented in the management of 48% of patients. Of interest, there was closer correct interpretation of pulmonary functions between family physicians and pulmonologists in patients who had asthma, versus those with COPD.