Pitfalls in Pulmonary Function Testing

Abstract

Assessment of respiratory function is an integral component of the clinical examination and can be performed at the bedside or in the office. In a small proportion of patients, further studies in a laboratory may be necessary. The most serious pitfalls in pulmonary function testing arise in relation to the appropriate performance of the test, the prediction of 'normal' values, and the interpretation of the test results. Provided that care is taken to assure the validity of all measurements, that the equipment is properly calibrated, and that basic principles of pulmonary physiology are kept in mind, evaluation of simple variables, along with tests carried out in the pulmonary function laboratory, provides an assessment of impairment. In particular, lung volume must be considered whenever the elastic properties and flow resistance or simple tests reflecting these properties are interpreted. Similarly, the assessment of arterial blood gas tensions must be accompanied by calculation of the P(A-a)02. With proper evaluation of these measurements, one can elucidate the mechanism of production of pulmonary disturbances and identify appropriate therapy. Most important, repeated assessments are essential if one is to follow the course of a disease process or evaluate the impact of therapeutic regimes.