Alongside imaging techniques, pulmonary function testing helps in the diagnosis of underlying disorders such as asthma and chronic obstructive pulmonary disease (COPD) or fibrosing lung disease. However, disease severity grading is also important, as well as disease follow-up under therapy. The value of spirometry as a first-line diagnostic test, whole-body plethysmography in advanced diagnostics, the measurement of transfer factor, as well as blood gas analysis are outlined. The importance of spiroergometry, echocardiography, and right-heart catheterization, particularly in the functional assessment of pulmonary vascular disorders, is described. Tests in respiratory sleep medicine, such as polysomnography, as well as tests for diagnosing chronic respiratory failure, are part of the respiratory physician's diagnostic armamentarium.
