INTRODUCTION
Cystic fibrosis (CF) is the most common life-limiting genetic disease in
Caucasians and pulmonary disease remains the primary etiology of
morbidity and mortality in CF. Lung disease in CF is present during
infancy and events early in life play a critical role in long-term
outcomes. Early Pseudomonas aeruginosa (Pa) infection, elevated
free neutrophil elastase in bronchoalveolar lavage fluid, history of
wheeze and history of hospitalizations are some risk factors in infancy
and early childhood associated with lower lung function and/or
bronchiectasis in later childhood 1-4. Nutritional
status within the first years of life predicts lung function in later
childhood 4-6. Despite the advent of newborn screening
(NBS), CF lung disease continues to occur in the youngest population;
however, it is often present without symptoms 7-11.
Given that lung function in infancy tracks into preschool years12-14, identifying sensitive clinical markers of early
disease is imperative. Early identification will lead to treatment and
intervention, ultimately preventing or mitigating CF lung disease.
The ability to assess lung disease during infancy remains challenging15-17. Chest computed tomography is a sensitive
measure of early CF lung disease, but requires sedation and exposure to
radiation 1,18. Infant pulmonary function tests
(iPFTs) detect early lung disease but require sedation and a high level
of technical skill 16,19. The success rate of
obtaining forced expiratory flows (FEF) via the raised volume rapid
thoracoabdominal technique (RVRTC) in multicenter clinical trials is not
as high as obtaining functioning residual capacity via plethysmography
(FRCpleth) 16,17,19. Although
FRCpleth has been measured in studies of infants with
CF, data from infants diagnosed via NBS are more limited, with only one
other cohort previously described 7,16,20,21. Given
that early CF lung disease begins in the small peripheral airways, FRC
may be a more sensitive measure of early CF lung disease when compared
to forced expiratory flows. In CF NBS infants, there is limited
information correlating FRC with clinically useful indicators of early
lung disease.
The objective of our study was to identify clinical features associated
with abnormal lung function, specifically FRC, in CF NBS infants. We
hypothesized that poor nutritional status in the first 6-12 months of
life is associated with more hyperinflation at 12-24 months of age.