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


CONCLUSIONS
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.
Kraemer
Richard
R
Department of Paediatrics, University of Berne, Inselspital CH-3010 Berne, Switzerland. richard.kraemer@insel.ch
Latzin
Philipp
P
Pramana
Isabelle
I
Ballinari
Pietro
P
Gallati
Sabina
S
Frey
Urs
U
D000293:Adolescent; D000367:Age Factors; D000403:Airway Resistance; D001784:Blood Gas Analysis; D002245:Carbon Dioxide / Q000097:blood*; D002648:Child; D002675:Child, Preschool; D003550:Cystic Fibrosis / Q000097:blood / Q000235:genetics / Q000503:physiopathology*; D019005:Cystic Fibrosis Transmembrane Conductance Regulator / Q000235:genetics; D018450:Disease Progression; D005260:Female; D005540:Forced Expiratory Flow Rates; D005541:Forced Expiratory Volume; D005652:Functional Residual Capacity; D020022:Genetic Predisposition to Disease; D006801:Humans; D016014:Linear Models; D016015:Logistic Models; D008168:Lung / Q000503:physiopathology*; D008297:Male; D010100:Oxygen / Q000097:blood*; D010641:Phenotype; D011446:Prospective Studies; D011659:Pulmonary Gas Exchange / Q000235:genetics; D012042:Registries; D013997:Time Factors
C505032:CFTR protein, human; D019005:Cystic Fibrosis Transmembrane Conductance Regulator; D002245:Carbon Dioxide; D010100:Oxygen