Pulmonary Function Tests

Abstract

Pulmonary function tests provide quantitative assessment of physiological properties in respiratory system including the lungs and chest wall. Spirometry is the first step as a screening and diagnostic test to investigate the existence and severity of obstructive or restrictive ventilatory disorders. Second is the measurement of lung volumes. Another technique is used to measure functional residual capacity, because absolute gas volume remaining in the lungs cannot be measured using spirometer. Measurements of lung volumes enable us to evaluate the changes in the mechanical balance between the lungs and chest wall, due to pulmonary or extrapulmonary diseases. As the next step, diffusing capacity for carbon monoxide can be measured to assess the capacity of the lung to exchange gas across the alveolar-capillary interface. Arterial blood gases that reflect the final output from respiratory system as the organs for gas exchange are introduced for the diagnosis of respiratory failure and acid-base disturbances. Additional pulmonary function tests including bronchoprovocation test, the measurement of respiratory impedance, and field walking tests (the 6-min walk test, incremental shuttle walk test, and endurance shuttle walk test) may be performed for further examinations in specific clinical circumstances. All these pulmonary function tests are useful for the assessment of pulmonary diseases in the clinical settings and clinical researches, especially in conjunction with morphological assessment using image diagnosis.