Pulmonary function testing is an important tool in the evaluation of children who have or are suspected of having lung disease. Of particular importance, pulmonary function testing provides objective and reproducible measurements, which then can be used to follow the response to therapy. The measurements of air flow and lung volumes are the mechanical pulmonary function tests used most commonly. However, measurements of the efficiency of gas exchange also are considered a test of pulmonary function and can be assessed by such methods as arterial blood gas and oximetry. This article focuses on those tests readily available to the pediatrician in the office or hospital.
Measuring pulmonary function regularly is analogous to measuring blood pressure in patients who have hypertension, allowing the physician to follow a measurement directly associated with the pulmonary disease process. As with other clinical tests, pulmonary function measurements are most effective when used to answer a specific question about the patient. For example, in a child who presents having a persistent cough and a family history of asthma, the diagnosis may be asthma, and the question "Does the child have airflow obstruction consistent with asthma?" can be answered by spirometry.
The parameters commonly measured in the assessment of respiratory function are lung volumes, air flows and timed volumes, and airway reactivity.