Air trapping in children: evaluation with dynamic lung densitometry with spiral CT.

Abstract

To evaluate the feasibility of the use of a simple method of dynamic lung densitometry with spiral computed tomography (CT) to differentiate air trapping from compensatory hyperinflation in children. Eight children (mean age, 4 years 2 months) who had focal areas of radiolucency on chest radiographs underwent spiral CT (5-second acquisition time, fixed table position) during quiet breathing. Data were reconstructed with 0.7-second temporally overlapping scans. Lung attenuation in selected regions of interest was plotted against time. In children with air trapping (n = 5), mean lung attenuation (+/- 1 standard deviation) in hyperlucent regions was -815 HU +/- 52, and mean respiratory excursion was 28 HU +/- 7. In patients with compensatory hyperinflation (n = 4), mean lung attenuation was -664 HU +/- 31, and respiratory excursion was 84 HU +/- 15. The differences were statistically significant (P = .001 for mean attenuation; P < .0005 for respiratory excursion). Dynamic spiral CT lung densitometry is a quick, simple method for quantitative confirmation of the presence of air trapping and differentiation from compensatory hyperinflation.