title: Growth of the lung parenchyma early in life.
abstract: BACKGROUND
  Early in life, lung growth can occur by alveolarization, an increase in the number of alveoli, as well as expansion. We hypothesized that if lung growth early in life occurred primarily by alveolarization, then the ratio of pulmonary diffusion capacity of carbon monoxide (Dl(CO)) to alveolar volume (V(A)) would remain constant; however, if lung growth occurred primarily by alveolar expansion, then Dl(CO)/V(A) would decline with increasing age, as observed in older children and adolescents.
  
  
  OBJECTIVE
  To evaluate the relationship between alveolar volume and pulmonary diffusion capacity early in life.
  
  
  METHODS
  In 50 sleeping infants and toddlers, with equal number of males and females between the ages of 3 and 23 months, we measured Dl(CO) and V(A) using single breath-hold maneuvers at elevated lung volumes.
  
  
  RESULTS
  Dl(CO) and V(A) increased with increasing age and body length. Males had higher Dl(CO) and V(A) when adjusted for age, but not when adjusted for length. Dl(CO) increased with V(A); there was no gender difference when Dl(CO) was adjusted for V(A). The ratio of Dl(CO)/V(A) remained constant with age and body length.
  
  
  CONCLUSIONS
  Our results suggest that surface area for diffusion increases proportionally with alveolar volume in the first 2 years of life. Larger Dl(CO) and V(A) for males than females when adjusted for age, but not when adjusted for length, is primarily related to greater body length in boys. The constant ratio for Dl(CO)/V(A) in infants and toddlers is consistent with lung growth in this age occurring primarily by the addition of alveoli rather than the expansion of alveoli.
authors.affiliation: Department of Pediatrics, Indiana University Medical Center, James Whitcomb Riley Hospital for Children, Herman B. Wells Center for Pediatric Research, Indianapolis, Indiana 46202-5225, USA.
authors.forename: Juan E
authors.initials: JE
authors.lastname: Balinotti
authors.forename: Christina J
authors.initials: CJ
authors.lastname: Tiller
authors.forename: Conrado J
authors.initials: CJ
authors.lastname: Llapur
authors.forename: Marcus H
authors.initials: MH
authors.lastname: Jones
authors.forename: Risa N
authors.initials: RN
authors.lastname: Kimmel
authors.forename: Cathy E
authors.initials: CE
authors.lastname: Coates
authors.forename: Barry P
authors.initials: BP
authors.lastname: Katz
authors.forename: James T
authors.initials: JT
authors.lastname: Nguyen
authors.forename: Robert S
authors.initials: RS
authors.lastname: Tepper
mesh_terms: D005260:Female; D006801:Humans; D007223:Infant; D008168:Lung / Q000254:growth & development*; D008176:Lung Volume Measurements; D008297:Male; D016017:Odds Ratio; D011650:Pulmonary Alveoli / Q000502:physiology; D011653:Pulmonary Diffusing Capacity; D012016:Reference Values; D012044:Regression Analysis; D012189:Retrospective Studies