Passive respiratory mechanics to assess lung function in infants.

In the last decade, the development of a number of ingenious techniques has led to the possibility of evaluating respiratory mechanics from the neonate up to children 3-4 yrs of age. Among these methods, the single-breath occlusion (SBO) technique and the multiple occlusion (MO) technique have gained extensive acceptance, and are used both in spontaneously breathing and mechanically-ventilated infants. These techniques allow the assessment of the passive mechanics of the total respiratory system (compliance, resistance and time constant), by evoking the Hering-Breuer inflation reflex, which results in relaxation of both inspiratory and expiratory muscles. These methods are suitable for repeated assessment in small infants and for longitudinal studies, because of their low invasivity, high reproducibility and relatively simple application. Pulmonary function tests may represent a useful guide in diagnosis, monitoring, prediction of outcome, and management assessment in infants and children with lung diseases. However all these techniques are limited by implicit assumptions and further developments towards simpler methods are needed.