This document provides a comprehensive guide to the standardisation of lung function testing, focusing on the measurement of lung volumes. It outlines the definitions, subdivisions, and measurement techniques for lung volumes, including functional residual capacity (FRC), residual volume (RV), total lung capacity (TLC), and other related volumes. The document integrates recommendations from the American Thoracic Society (ATS) and European Respiratory Society (ERS) Task Force on pulmonary function standards, as well as input from a previous National Heart, Lung, and Blood Institute (NHLBI) workshop. It discusses various techniques for measuring absolute lung volumes, including body plethysmography, nitrogen washout, gas dilution, and imaging techniques such as conventional radiographs, computed tomography (CT), and magnetic resonance imaging (MRI). The document emphasizes the importance of accurate and reproducible measurements of lung volumes, particularly in infants, children, and adults. It provides detailed guidelines for patient preparation, measurement techniques, quality control, and calculations. For body plethysmography, the document describes the theory, equipment, and measurement procedures, including the use of Boyle's Law for calculations. It also addresses the challenges of measuring lung volumes in patients with obstructive lung disease and the need for alternative methods when standard techniques are not feasible. For nitrogen washout, the document outlines the theory, equipment, and measurement techniques, including the use of nitrogen analysers and the importance of accurate measurements to avoid errors. For helium dilution, the document explains the method of equilibrating helium in the lungs and calculating lung volumes based on changes in helium concentration. The document also discusses the use of imaging techniques, noting their potential for measuring lung volumes in patients who cannot cooperate, but highlighting the limitations and assumptions associated with these methods. The document concludes with recommendations for the standardisation of lung volume measurements, emphasizing the need for accurate, reproducible, and clinically relevant methods to assess lung function in various patient populations. It also addresses the importance of quality control, calibration, and the use of appropriate equipment to ensure reliable and consistent results.This document provides a comprehensive guide to the standardisation of lung function testing, focusing on the measurement of lung volumes. It outlines the definitions, subdivisions, and measurement techniques for lung volumes, including functional residual capacity (FRC), residual volume (RV), total lung capacity (TLC), and other related volumes. The document integrates recommendations from the American Thoracic Society (ATS) and European Respiratory Society (ERS) Task Force on pulmonary function standards, as well as input from a previous National Heart, Lung, and Blood Institute (NHLBI) workshop. It discusses various techniques for measuring absolute lung volumes, including body plethysmography, nitrogen washout, gas dilution, and imaging techniques such as conventional radiographs, computed tomography (CT), and magnetic resonance imaging (MRI). The document emphasizes the importance of accurate and reproducible measurements of lung volumes, particularly in infants, children, and adults. It provides detailed guidelines for patient preparation, measurement techniques, quality control, and calculations. For body plethysmography, the document describes the theory, equipment, and measurement procedures, including the use of Boyle's Law for calculations. It also addresses the challenges of measuring lung volumes in patients with obstructive lung disease and the need for alternative methods when standard techniques are not feasible. For nitrogen washout, the document outlines the theory, equipment, and measurement techniques, including the use of nitrogen analysers and the importance of accurate measurements to avoid errors. For helium dilution, the document explains the method of equilibrating helium in the lungs and calculating lung volumes based on changes in helium concentration. The document also discusses the use of imaging techniques, noting their potential for measuring lung volumes in patients who cannot cooperate, but highlighting the limitations and assumptions associated with these methods. The document concludes with recommendations for the standardisation of lung volume measurements, emphasizing the need for accurate, reproducible, and clinically relevant methods to assess lung function in various patient populations. It also addresses the importance of quality control, calibration, and the use of appropriate equipment to ensure reliable and consistent results.