Draper et al. Standardised system to categorise units and network comparisons

	Days of mechanical respiratory support	Consultants with >50% dedicated neonatal sessions	Study categorisation, n (network designations L3, L2, L1)
High activity	2000+	4+	25 (24, 1, 0)
Moderate activity	500–1999	1–3	61 (21, 37, 3)
Low activity	<500	<1	96 (1, 46, 49)