Introduction

Preschool children with cystic fibrosis (PwCF) are mostly not able to follow breath-hold commands of chest CT for which reason CTs are performed either by free-breathing or pressure-controlled protocol under general anesthesia, both resulting in (expiratory) scans near FRC but not RV. CTs taken in lateral decubitus position while free breathing results in an expiratory lung volume of the dependent lung near RV and of the ?inspiratory? contralateral lung between FRC and TLC.

Aims

To evaluate the feasibility and sensitivity of lateral decubitus CT to detect structural lung disease in PwCF.

Methods
PwCF who had a lateral decubitus CT at Copenhagen CF-Center were enrolled. For each CT, one left lateral and one right lateral CT was scored by PRAGMA-CF to quantify on the inspiratory CT the %volume occupied by bronchiectasis (%BE), mucus plugging, airway wall thickening, atelectasis(%Atel), and sum of all airway abnormalities (%Dis), and on the expiratory CT Trapped air (%TA). Lung volumes were scored by Myrian. Results are mean[SD].

Results
48 PwCF (age 1.98[1.13] years) with 73 CTs were included. 4% of left and 3% of right position CTs had poor quality. BE, Atel, and TA were observed on 81%, 74%, and 51% of CTs, with %BE 0.67[0.92], %Atel 2.40[3.98], %TA 3.14[7.61], and %Dis 5.58[6.88]. Lung volume was measured on 58 CTs (15 excluded because of slice increment >3mm). Lung volumes for inspiratory and expiratory CTs were 508.7[199.4]mL and 344[137.7]mL. Mean inspiratory/expiratory volume ratio was 1.48[0.13].

Conclusions
Lateral decubitus CTs using PRAGMA-CF is a feasible and sensitive technique to detect and monitor structural lung abnormalities in PwCF.