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Open Access Research

Long-term gas exchange characteristics as markers of deterioration in patients with cystic fibrosis

Richard Kraemer1*, Philipp Latzin12, Isabelle Pramana12, Pietro Ballinari4, Sabina Gallati13 and Urs Frey12

Author Affiliations

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

2 Division of Paediatric Respiratory Medicine, Department of Paediatrics, University of Berne, Inselspital, CH-3010 Berne, Switzerland

3 Division of Human Genetics, Department of Clinical Research, University of Berne, CH-3010 Berne. Switzerland

4 Institute of Psychology, University of Berne, Muesmattstr. 45, CH-3000 Bern Switzerland

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Respiratory Research 2009, 10:106  doi:10.1186/1465-9921-10-106

Published: 12 November 2009

Abstract

Background and Aim

In patients with cystic fibrosis (CF) the architecture of the developing lungs and the ventilation of lung units are progressively affected, influencing intrapulmonary gas mixing and gas exchange. We examined the long-term course of blood gas measurements in relation to characteristics of lung function and the influence of different CFTR genotype upon this process.

Methods

Serial annual measurements of PaO2 and PaCO2 assessed in relation to lung function, providing functional residual capacity (FRCpleth), lung clearance index (LCI), trapped gas (VTG), airway resistance (sReff), and forced expiratory indices (FEV1, FEF50), were collected in 178 children (88 males; 90 females) with CF, over an age range of 5 to 18 years. Linear mixed model analysis and binary logistic regression analysis were used to define predominant lung function parameters influencing oxygenation and carbon dioxide elimination.

Results

PaO2 decreased linearly from age 5 to 18 years, and was mainly associated with FRCpleth, (p < 0.0001), FEV1 (p < 0.001), FEF50 (p < 0.002), and LCI (p < 0.002), indicating that oxygenation was associated with the degree of pulmonary hyperinflation, ventilation inhomogeneities and impeded airway function. PaCO2 showed a transitory phase of low PaCO2 values, mainly during the age range of 5 to 12 years. Both PaO2 and PaCO2 presented with different progression slopes within specific CFTR genotypes.

Conclusion

In the long-term evaluation of gas exchange characteristics, an association with different lung function patterns was found and was closely related to specific genotypes. Early examination of blood gases may reveal hypocarbia, presumably reflecting compensatory mechanisms to improve oxygenation.