Table 2 Lung volume according to position.

	PMA (weeks)	No.	Postnatal age (days)	Weight (g)	Prone FRC (ml/kg)	Supine FRC (ml/kg)	p Value
Non‐oxygen‐dependent infants
	32	12	17 (7–41)	1432 (885–1720)	22.1 (17.1–30.2)	18.2 (12.9–36.0)	0.01
	34	15	33 (21–53)	1782 (1180–2004)	24.4 (17.5–33.9)	20.4 (13.6–37.4)	0.003
Oxygen‐dependent infants
	32	7	37 (18–58)	1453 (954–1546)	22.7 (17.9–37.1)	19.0 (14.2–25.1)	0.04
	34	13	47 (30–72)	1762 (1312–2170)	20.9 (14.8–24.6)	17.9 (13.9–26.3)	0.3
	36	16	73 (39–92)	1916 (1168–2834)	20.8 (12.7–27.8)	17.5 (9.8–30.8)	0.2
	38	11	84 (54–103)	2325 (1534–3080)	23.2 (12.6–27.7)	18.7 (12.6–27.2)	0.04

FRC, functional residual capacity; PMA, postmenstrual age.

Data are median (range).