Normal Lung Development in Children: The Results of a Review of 940 3-Dimensional CT Scan Reconstructions of the Thoracic Cavity in Normal Children

Background: Expansion thoracoplasty is a new treatment philosophy and surgical technique for the management of complex spinal deformities in the growing child. This approach attempts to simultaneously increase thoracic volume, nurture growth of the immature lung, control progressive spinal deformity, and avoid early spinal fusion and the associated risk of thoracic insufficiency syndrome at the completion of growth. The potential or actual effect of spinal deformity on lung growth and function currently must be estimated pulmonary function testing, radiographs, or CT scans. However, most significant progressive spinal deformity presents at an age before accurate pulmonary function testing is available. Presently, there are there few anthropometric data sets on the normal standards for growth and development of the lungs in these early age groups. This lack of normal standards makes it difficult to use anthropometric data to assess the severity of respiratory compromise in children with spinal and thoracic deformities and to analyze the effects of expansion thoracoplasty on the growth and volume of the lungs.

Methods: In an effort to establish standards for the normal size of the lungs as a function of age, we analyzed 940 surveillance CT scans of a normal chest obtained over the past three years at one institution. Using three-dimensional reconstructions of CT scan data, we have constructed a model of age-based normative data for lung development in children. A software package designed for volumetric analysis of CT and MRI data (Voxtool Version 3.0.26e, GE Advantage Windows Workstation 4.0, General Electric, Milwaukee, WI) was used to generate a 3-dimensional, volumetric model of the lungs for each patient. The volumes of the right, left, and complete pulmonary organ system were then determined. Pulmonary volume data were plotted as a function of age and values for the 5th, 10th, 25th, 50th, 75th, 90th, and 95th percentiles were calculated using statistical techniques used by the Centers for Disease Control (CDC) to plot normative data for the anthropometric status of children for the CDC growth charts.

Significance: The establishment of normative data for the volume of the lungs as a function of age provides as an important clinical tool in the evaluation of the respiratory status of children with complex congenital and infantile spinal deformities. The ability to obtain these data using CT scan images makes it possible to assess pulmonary development at ages where traditional pulmonary function testing is not possible. These normative data, when used for comparison to historical control populations with complex spinal deformity, will be instrumental in demonstrating the clinical efficacy of expansion thoracoplasty as an alternative to spinal fusion in young, growing children.