Lung Growth in Infants and Toddlers Assessed by Multi-slice Computed Tomography

Rationale and Objectives

Postnatal lung growth and development have primarily been evaluated from a very limited number of autopsied lungs, but it remains unclear whether alveolarization of the lung is complete during infancy and whether the conducting airways grow proportionately. The purpose of this study was to evaluate lung growth and development in vivo in infants and toddlers using multislice computed tomography.

Materials and Methods

Thirty-eight subjects (14 male, 24 female) aged 17 to 142 weeks underwent low-dose volumetric high-resolution computed tomographic imaging at an inflation pressure of 20 cm H₂O during an induced respiratory pause. Lung volume and weight were determined, as well as airway dimensions (inner and outer area and wall area) for the trachea and the next three to four generations.

Results

Lung volume, air volume, and tissue volume increased linearly with body length. The air and tissue components of the lung parenchyma increased at a constant rate with each other. In addition, airway caliber decreased with increasing generation from the trachea into each lobe. Airway caliber was also correlated with body length; however, there was no interaction effect between airway generation and body length on transformed airway size.

Conclusions

In vivo assessment suggests that the growth of the lung parenchyma in infants and toddlers occurred with a constant relationship between air volume and lung tissue, which is consistent with lung growth occurring primarily by the addition of alveoli rather than the expansion of alveoli. In addition, the central conducting airways grow proportionately in infants and toddlers. This information may be important for evaluating subjects with arrested lung development.

Key Words: Airway size, lung parenchyma, lung volume