Pulmonary function tests in preschool children with cystic fibrosis

Pulmonary function tests have rarely been assessed in preschool children with cystic fibrosis (CF). The objective of this multicenter study was to compare pulmonary function in 39 preschool children with CF (height, 90-130 cm; 16 homozygous DeltaF508) and in 79 healthy control children. Functional residual capacity (helium dilution technique) and expiratory interrupter resistance (Rint(exp)) (interrupter technique) were measured. As compared with control children, children with CF had significantly higher Rint(exp), expressed as absolute values and as Z-scores (1.05+/-0.36 versus 0.80+/-0.20 kPa-L . second, p<0.0001; and 1.31+/-1.72 versus 0.19+/-0.97, p<0.0001), and significantly lower specific expiratory interrupter conductance (1.29+/-0.34 versus 1.63+/-0.43 kPa(-1) - second, p<0.0001). The effect of the bronchodilator salbutamol on Rint(exp) was not significantly different between children with CIF and control children. Rint(exp) Z-scores were significantly higher in children with CIF who were exposed to passive smoke (n = 8) (p<0.03). Children with CF and with a history of respiratory symptoms (n = 31) had significantly higher functional residual capacity Z-scores (p<0.02) and lower specific expiratory interrupter conductance Z-scores (p<0.04). Genotype did not influence the data.We conclude that Rint(exp) and functional residual capacity measurements may help to follow young children with CF who are unable to perform reproducible forced expiratory maneuvers.