Progression of pulmonary hyperinflation and trapped gas associated with genetic and environmental factors in children with cystic fibrosis

Richard Kraemer¹^,2 , David N Baldwin² , Roland A Ammann¹ , Urs Frey¹^,2 and Sabina Gallati¹^,3

¹Department of Paediatrics, University of Berne, Inselspital CH-3010 Berne, Switzerland.

²Division of Pediatric Respiratory Medicine, Department of Pediatrics, University of Berne, Inselspital, CH-3010 Berne, Switzerland.

³Division of Human Genetics, Department of Pediatrics, University of Berne,, Inselspital, CH-3010 Berne, Switzerland.

author email corresponding author email

Respiratory Research 2006, 7:138doi:10.1186/1465-9921-7-138


Published:	30 November 2006

Abstract

Background

Functional deterioration in cystic fibrosis (CF) may be reflected by increasing bronchial obstruction and, as recently shown, by ventilation inhomogeneities. This study investigated which physiological factors (airway obstruction, ventilation inhomogeneities, pulmonary hyperinflation, development of trapped gas) best express the decline in lung function, and what role specific CFTR genotypes and different types of bronchial infection may have upon this process.

Methods

Serial annual lung function tests, performed in 152 children (77 males; 75 females) with CF (age range: 6–18 y) provided data pertaining to functional residual capacity (FRC_pleth, FRC_MBNW), volume of trapped gas (V_TG), effective specific airway resistance (sR_eff), lung clearance index (LCI), and forced expiratory indices (FVC, FEV₁, FEF₅₀).

Results

All lung function parameters showed progression with age. Pulmonary hyperinflation (FRC_pleth> 2SDS) was already present in 39% of patients at age 6–8 yrs, increasing to 67% at age 18 yrs. The proportion of patients with V_TG> 2SDS increased from 15% to 54% during this period. Children with severe pulmonary hyperinflation and trapped gas at age 6–8 yrs showed the most pronounced disease progression over time. Age related tracking of lung function parameters commences early in life, and is significantly influenced by specific CFTR genotypes. The group with chronic P. aeruginosa infection demonstrated most rapid progression in all lung function parameters, whilst those with chronic S. aureus infection had the slowest rate of progression. LCI, measured as an index of ventilation inhomogeneities was the most sensitive discriminator between the 3 types of infection examined (p < 0.0001).

Conclusion

The relationships between lung function indices, CFTR genotypes and infective organisms observed in this study suggest that measurement of other lung function parameters, in addition to spirometry alone, may provide important information about disease progression in CF.