Lung function testing in infants.

During recent years, there has been rapid development in the availability and application of pulmonary function tests in infants and young children. Whereas original methods were based on adaptations of classical techniques, over the past decade there has been an increasing trend towards developing less complex techniques specifically for use in infants and young children. Interpretation of these measurements requires a knowledge of respiratory physiology, and may be confounded by an unstable end expiratory level, compliant chest wall, dominance of the upper airways, difficulty in achieving flow limitation in healthy infants, and the variability of respiratory, lung or airway resistance which increases the difficulty of assessing the significance of changes in resistance as a result of treatment or challenge. Nevertheless, with care, the assessment of respiratory function during infancy and early childhood can increase knowledge of the growth and development of the respiratory system, and our understanding of the patho-physiological processes underlying respiratory diseases in early life. They also have the potential to provide valuable objective outcome measures in the quest for effective preventive and therapeutic strategies in respiratory medicine.