Lung function testing: Chronic lung disease of infancy

Abstract

Now that infants with chronic lung disease are reaching adulthood, it is possible to discern patterns of long-term abnormalities in lung function. These patterns indicate that the airway dysfunction in infancy has implications for airway dysfunction in later life. Most studies in later childhood and adolescence report changes in lung volumes, flow rates and prevalence of airway hyper-reactivity in children born prematurely with respiratory distress syndrome (RDS) requiring ventilatory support for more than thirty days, i.e., with classic bronchopulmonary dysplasia (BPD). Comparing the numerous studies of these children enables us to draw certain conclusions regarding the pathogenesis of these abnormalities. The longitudinal evaluation of lung function in infants born prematurely, with or without RDS or BPD, from infancy to early adulthood, may allow us to answer some important fundamental questions about lung and airway growth following premature birth and early lung injury. Some of these questions are: 1) Does prematurity per se lead to abnormal lung and airway function? 2) Does the severity of the neonatal insult correlate with later abnormalities in lung function? 3) What role does airway hyper-reactivity play in the airway dysfunction of later life? 4) Is airway function affected more severely than lung volumes? STUDIES IN INFANTS AND TODDLERSThe recent advances in our ability to assess lung function in infants show great promise in enhancing our understanding of the early abnormalities of infants with chronic lung disease of infancy. Airway function has been assessed by measurements of lung resistance by esophageal manometry and forced expiratory flows by the rapid thoracic compression technique. Low Vmax functional residual capacity (FRC) has been demonstrated in the first year of life in infants with BPD compared to full term infants,' and compared to full term and preterm controk2 Baraldi3 showed similar results in children to age 2 years, and Farstad4 demonstrated infants with BPD had lower flows at 1 and 2 years than did children with RDS alone. Airway conductance through the third year of life is lower in infants with BPD compared to full term and preterm control^,^ and forced expiratory flows by the rapid deflation technique are lower in BPD infants in this age group than in age matched controls.6 0 2001 Wiley-Liss, Inc.Lung volumes, specifically FRC, have also been measured. Gerhardt has shown, using nitrogen washout, that in the first year of life, lung volumes in infants with BPD are lower than in normal controls, whereas in the second and third years, they are higher than in control^.^ The switch from low to high lung volumes can be interpreted as evidence of increasing air trapping due to worsening airway disease during the first year of life. Alternatively, since nitrogen washout can underestimate lung volumes in patients with airway disease, it could indicate improving airway function. A recent study compared measurements of FRC by both nitrogen washout and body plethysmography in the first yea...

Neonatal respiratory status predicts longitudinal respiratory health outcomes in preterm infants

“…The introduction of antenatal steroids, postnatal surfactant therapy, and assisted ventilation, along with other advances in neonatal intensive care, has greatly improved the survival of small preterm infants. Nevertheless, viable preterm infants requiring supplemental oxygen support for an extended period of time may exhibit numerically reduced and structurally simplified alveoli and blunted pulmonary vascular development and are prone to have unfavorable respiratory health outcomes from infancy to adulthood, such as increased hospital admissions for respiratory illnesses, persistent airflow obstruction, and a poor capacity for gas exchange . Poor respiratory health (and thus reduced ventilatory reserve) has a detrimental effect on physical fitness .…”

“…numerically reduced and structurally simplified alveoli and blunted pulmonary vascular development 1 and are prone to have unfavorable respiratory health outcomes from infancy to adulthood, 2,3 such as increased hospital admissions for respiratory illnesses, 4,5 persistent airflow obstruction, 6 and a poor capacity for gas exchange. 7 Poor respiratory health (and thus reduced ventilatory reserve) has a detrimental effect on physical fitness.…”