title: Impact of a physiologic definition on bronchopulmonary dysplasia rates.
abstract: OBJECTIVE
  Bronchopulmonary dysplasia (BPD) is the endpoint of many intervention trials in neonatology, yet the outcome measure when based solely on oxygen administration may be confounded by differing criteria for oxygen administration between physicians. We previously reported a technique to standardize the definition of BPD between sites by using a timed room-air challenge in selected infants. We hypothesized that a physiologic definition of BPD would reduce the variation in observed rates of BPD among different neonatal centers. Methodology. A total of 1598 consecutive inborn premature infants (501-1249 g birth weight) who remained hospitalized at 36 weeks' postmenstrual age were prospectively assessed and assigned an outcome with both a clinical definition and physiologic definition of BPD. The clinical definition of BPD was oxygen supplementation at exactly 36 weeks' postmenstrual age. The physiologic definition of BPD was assigned at 36 +/- 1 weeks' postmenstrual age and included 2 distinct subpopulations. First, neonates on positive pressure support or receiving >30% supplemental oxygen with saturations between 90% and 96% were assigned the outcome BPD and not tested further. Second, those receiving < or =30% oxygen or effective oxygen >30% with saturations >96% underwent a room-air challenge with continuous observation and oxygen-saturation monitoring. Outcomes of the room-air challenge were "no BPD" (saturations > or =90% during weaning and in room air for 30 minutes) or "BPD" (saturation <90%). At the conclusion of the room-air challenge, all infants were returned to their baseline oxygen levels. Safety (apnea, bradycardia, increased oxygen use) and outcomes of the physiologic definition versus the clinical definition were assessed.
  
  
  RESULTS
  A total of 560 (35.0%) neonates were diagnosed with BPD by the clinical definition of oxygen use at 36 weeks' postmenstrual age. The physiologic definition diagnosed BPD in 398 (25.0%) neonates in the cohort. All infants were safely studied. There were marked differences in the impact of the definition on BPD rates between centers (mean reduction: 10%; range: 0-44%). Sixteen centers had a decrease in their BPD rate, and 1 center had no change in their rate.
  
  
  CONCLUSIONS
  The physiologic definition of BPD reduced the overall rate of BPD and reduced the variation among centers. Significant center differences in the impact of the physiologic definition were seen, and differences remained even with the use of this standardized definition. The magnitude of the change in BPD rate is comparable to the magnitude of treatment effects seen in some clinical trials in BPD. The physiologic definition of BPD facilitates the measurement of BPD as an outcome in clinical trials and the comparison between and within centers over time.
authors.affiliation: Rainbow Babies and Childrens Hospital, Department of Pediatrics, Case Case Western Reserve University, 11100 Euclid Ave, Mailstop 6010, Cleveland, OH 44106, USA. mcw3@po.cwru.edu
authors.forename: Michele C
authors.initials: MC
authors.lastname: Walsh
authors.forename: Qing
authors.initials: Q
authors.lastname: Yao
authors.forename: Patricia
authors.initials: P
authors.lastname: Gettner
authors.forename: Ellen
authors.initials: E
authors.lastname: Hale
authors.forename: Monica
authors.initials: M
authors.lastname: Collins
authors.forename: Angelita
authors.initials: A
authors.lastname: Hensman
authors.forename: Ruth
authors.initials: R
authors.lastname: Everette
authors.forename: Nancy
authors.initials: N
authors.lastname: Peters
authors.forename: Nancy
authors.initials: N
authors.lastname: Miller
authors.forename: Gerry
authors.initials: G
authors.lastname: Muran
authors.forename: Kathy
authors.initials: K
authors.lastname: Auten
authors.forename: Nancy
authors.initials: N
authors.lastname: Newman
authors.forename: Gina
authors.initials: G
authors.lastname: Rowan
authors.forename: Cathy
authors.initials: C
authors.lastname: Grisby
authors.forename: Kathy
authors.initials: K
authors.lastname: Arnell
authors.forename: Lucy
authors.initials: L
authors.lastname: Miller
authors.forename: Bethany
authors.initials: B
authors.lastname: Ball
authors.forename: Georgia
authors.initials: G
authors.lastname: McDavid
mesh_terms: D001049:Apnea; D001919:Bradycardia; D001997:Bronchopulmonary Dysplasia / Q000175:diagnosis* / Q000453:epidemiology / Q000503:physiopathology* / Q000628:therapy; D006801:Humans; D007231:Infant, Newborn; D007234:Infant, Premature; D019102:Infant, Very Low Birth Weight; D015588:Observer Variation; D010100:Oxygen / Q000097:blood; D010102:Oxygen Inhalation Therapy
chemical_list: D010100:Oxygen