Advances in Pediatric Lung Function Testing Techniques

Background Appropriate interpretation of pulmonary function tests (PFTs) involves the classification of observed values as within/outside the normal range based on a reference population of healthy individuals, integrating knowledge of physiologic determinants of test results into functional classifications, and integrating patterns with other clinical data to estimate prognosis. In 2005, the American Thoracic Society and the European Respiratory Society jointly adopted technical standards for the interpretation of PFTs. We aimed to update the 2005 recommendations and incorporate evidence from recent literature to establish new standard for PFT interpretation. Methods This technical standards document was developed by an international joint task force, appointed by the European Respiratory Society and the American Thoracic Society with multidisciplinary expertise in conducting and interpreting pulmonary function tests, and developing international standards. A comprehensive literature review was conducted, and published evidence was reviewed. Results Recommendations for the choice of reference equations and limits of normal of the healthy population to identify individuals with unusually low or high results, respectively are discussed. Interpretation strategies for bronchodilator responsiveness testing, limits of natural changes over time and severity are also updated. Interpretation of measurements made by spirometry, lung volumes and gas transfer are described as they relate to underlying pathophysiology with updated classification protocols of common impairments. Conclusions PFTs interpretation must be complemented with clinical expertise and consider the inherent biological variability of the test and the uncertainty of the test result to ensure appropriate interpretation of an individual's lung function measurements.

Oscillometry (also known as the forced oscillation technique) measures the mechanical properties of the respiratory system (upper and intrathoracic airways, lung tissue and chest wall) during quiet tidal breathing, by the application of an oscillating pressure signal (input or forcing signal), most commonly at the mouth. With increased clinical and research use, it is critical that all technical details of the hardware design, signal processing and analyses, and testing protocols are transparent and clearly reported to allow standardisation, comparison and replication of clinical and research studies. Because of this need, an update of the 2003 European Respiratory Society (ERS) technical standards document was produced by an ERS task force of experts who are active in clinical oscillometry research. The aim of the task force was to provide technical recommendations regarding oscillometry measurement including hardware, software, testing protocols and quality control. The main changes in this update, compared with the 2003 ERS task force document are 1) new quality control procedures which reflect use of “within-breath” analysis, and methods of handling artefacts; 2) recommendation to disclose signal processing, quality control, artefact handling and breathing protocols ( e.g. number and duration of acquisitions) in reports and publications to allow comparability and replication between devices and laboratories; 3) a summary review of new data to support threshold values for bronchodilator and bronchial challenge tests; and 4) updated list of predicted impedance values in adults and children.