Physiologic Definition of Bronchopulmonary Dysplasia

One of the confounders to any study that looks at bronchopulmonary dysplasia (BPD) is the lack of a precise definition. Most neonates with BPD do not undergo lung biopsy or any physiologic test; thus, their pulmonary disease is defined clinically, on the basis of the sustained need for supplemental oxygen at 36 weeks postmenstrual age. The validity of this definition is supported by evidence that oxygen dependence at 36 weeks is predictive of long-term impairment in pulmonary function. An inherent limitation of defining BPD by the need for supplemental oxygen is that the need for oxygen is determined by individual physicians, rather than on the basis of a physiologic assessment. Published literature cites acceptable saturation ranges from 88-98%.

This observational study was conducted to design and test a physiologic definition for bronchopulmonary dysplasia at 36 weeks of life.

Infants were studied in a supine position with the pulse oximeter in position with good signal prior to collecting baseline data. Feedings and medications were given 30 minutes before the evaluation. Baseline data was collected on infant's current oxygen. Then, the infants were weaned to room air for 30 minutes. If saturations remain ≥90%, the infant was considered to have passed the oxygen reduction challenge (to NOT have BPD). The infant should then be placed back in his/her baseline oxygen. If the infant has saturations <90% for 5 continuous minutes or <80% for 15 seconds, the infant should be immediately placed back in his/her baseline oxygen, and the infant was considered to have NOT passed the challenge (to have BPD).

Inclusion criteria

• Infant with birthweight 401-1500 grams
• Alive at 36+1 week corrected age
• On supplemental oxygen as follows:
• A. Infants receiving oxygen by hood at rest:
• A1. Oxygen by hood <27% with majority* of saturations ≥ 90% in prior 24 hours.
• A2. Oxygen by hood 27-30% with majority* of saturations ≥ 96% in prior 24 hours
• B. Infants receiving oxygen by nasal cannula at restΔ:
• B1. Oxygen by nasal cannula <27% EFFECTIVE** oxygen and majority* of saturations ≥90% in prior 24 hours.
• B2. Oxygen by nasal cannula 27-30% EFFECTIVE** oxygen and majority* saturations ≥96% on prior 24 hours.
• C. Infants receiving room air by nasal cannula at ANY liter per minute (lpm) flow.

Exclusion criteria

• Need for mechanical ventilation or continuous positive airway pressure (CPAP)
• Oxygen by hood >30%
• Oxygen by nasal cannula >30% effective oxygen