Avaliação da função pulmonar em lactentes com displasia broncopulmonar através do teste de multiple breath washout

Abstract

Objectives : To assess if lung function could be used to predict risk of viral lower respiratory tract infections in prematurely born infants. In addition, we want to assess the impact of number and severity of LRTI episodes on lung growth. Methods : Longitudinal measurements of lung function by raised volume rapid thoracic compression technique were obtained in the first 6 months of life and after one year of follow-up in preterm infants. Number and severity of LRTI were recorded prospectively. The main outcome is an association between lung function measurements and number and severity of LRTI episodes. Results : Lung function tests were obtained in 71 preterm infants. There was a negative association between lung function and LRTI. Compared with infants with one or no LRTI episode (n=41), those with two or more episodes of LRTI (n=30) had significantly lower expiratory flows at first test (p<0.05 for zVEF0.5 zFEF50, zFEF75, zFEF25-75 and zFEFV0.5/FVC). No significant differences in gender distribution, gestational age, birth weight, school age siblings and smoke exposure were detected in relation to number or severity of LRTI. In the multivariate analysis, lung function and respiratory support in the neonatal intensive care unit was associated with higher number of LRTI. Severe LRTI was predicted by passive smoking and reduced zFEV0.5. In the longitudinal analysis, the change in lung function, adjusted for length, sex and smoke exposure during pregnancy was not affected by the number and severity of LRTI. Lung growth in this preterm birth cohort was not significantly different from a reference control group composed of full term babies. Conclusion : Our data suggest that lung function is a direct factor that mediates respiratory morbidity in premature infants. Lung function was a better predictor of number of LRTI than gestational age, sex and social demographics factors. The findings suggest that prenatal factors, particularly those that promote premature birth, determine lung development early in life. Postnatal events, like viral LRTI, do not have a detectable effect on lung growth.