Proposed definition for bronchopulmonary dysplasia (BPD) diagnosis and severity grading, from Jensen et al. [6]
| BPD category | Respiratory support requirement at 36 weeks postmenstrual age |
| No BPD | No support |
| Grade 1 BPD | Nasal cannula <2 L·min−1 |
| Grade 2 BPD | Nasal cannula >2 L·min−1 or noninvasive positive airway pressure |
| Grade 3 BPD | Invasive mechanical ventilation |