Lung volumes and lung volume recruitment in ARDS: a comparison between supine and prone position

Annals of Intensive Care

Table 2 Main characteristics of all patients in each position

Variable	Supine n = 20	Prone n = 20	p
PaO₂/FiO₂ (mm Hg)	210 ± 57	281 ± 109	0.021
PaCO₂ (mm Hg)	41 ± 8	42 ± 9	0.400
Peak airway pressure (cm H₂O)	41 ± 7	41 ± 6	0.284
Pplat (cm H₂O)	23 ± 4	23 ± 4	0.446
Compliance (ml/cm H₂O)	36 ± 11	37 ± 10	0.594
Δ Paw (cm H₂O)	13 ± 4	12 ± 4	0.446
FRC (ml)	965 ± 397	1140 ± 490	0.021
EELV (ml)	1566 ± 476	1832 ± 719	0.009
Vt delivered from ZEEP, that generated a Pplat equal to basal PEEP [ml (n = 16)]	333 ± 105	360 ± 127	0.073
Vrec [ml (n = 16)]	269 ± 186	324 ± 188	0.501
Dynamic strain at ZEEP	0.52 ± 0.23	0.44 ± 0.18	0.040
Dynamic strain at PEEP (n = 16)	0.38 ± 0.14	0.33 ± 0.13	0.020
Static strain at PEEP (n = 16)	0.51 ± 0.16	0.48 ± 0.13	0.438
Global strain at PEEP (n = 16)	0.89 ± 0.24	0.81 ± 0.18	0.121

Data are presented as mean ± SD. Dynamic strain at ZEEP = Vt/FRC; dynamic strain at PEEP = Vt/(FRC + Vrec); static strain at PEEP = (EELV − FRC)/(FRC + Vrec); global strain at PEEP = (EELV − FRC + Vt)/(FRC + Vrec)
EELV end-expiratory lung volume, FRC functional residual capacity, PEEP positive end-expiratory pressure, Pplat end-inspiratory plateau airway pressure, Vrec PEEP-induced lung volume recruitment, Vt tidal volume, Δ Paw driving airway pressure