Intrapulmonary gas distribution in healthy children.

Distribution of ventilation was evaluated in 54 healthy children (24 boys and 30 girls), aged 7-16 years by multibreath nitrogen washout (MBNW) curves, from which the moment ratios (m1: m0, m2: m0), the lung clearance index, the Becklake index and the ventilatory efficiency index (E 90%) was computed. Functional residual capacity (FRC) was calculated from the washout curve and compared with the thoracic gas volume (TGV) plethysmographically determined, as well as with the FRC determined by helium dilution. The study shows that MBNW can easily be performed during spontaneous breathing in children and provides specific indices of ventilation. These indices show no sex difference and are age-independent. Therefore, the data of the present study contradict some previous indirect findings suggesting that the distribution of air in the lungs would become more even with age. There are in contrast more convincing direct measurement data showing that airways grow isotropically relative to the lungs.