The flow/volume curve as a mass screening test with emphasis on quality control.

Air flow through the airways is influenced by different mechanical characteristics of the respiratory system and can be affected by pathological changes in the lungs. Lung volume is probably the most important independent variable determining air flow through the airways. Therefore, it is logical that lung volume should form the ordinate of a curve used to demonstrate the variation of airflow through the airways during forced inspiratory and expiratory manoeuvres. The flow/volume curve is in many ways superior to other measurements of lung function for clinical and epidemiological assessments. Most of the problems that have to be overcome in obtaining satisfactory and repeatable flow/volume curves are discussed and illustrated. A computer system which optimises quality control is described. By making use of this system, operator error can be reduced to a minimum. It is recommended that hard copies of the three efforts must be available and that all flow/volume measurements be controlled by a knowledgeable person before the results are entered in the records.