Table 1.

Distribution of tidal ventilation, tidal recruitment gas and nonaerated lung tissue in apical slice

Region	Mode	Tidal ventilation (% of tidal volume)	Tidal recruitment (% of total lung volume)	Gas volume (% of contained gas)	Nonaerated lung tissue (% of total lung volume)
Nondependent	SB-	46 ± 13	0.1 ± 0.2	56 ± 12	0.3 ± 0.6
	SB+	33 ± 31	0.0 ± 0.2	56 ± 6	0.4 ± 0.7
Dependent	SB-	54 ± 13	1.7 ± 1.9	44 ± 12	13.8 ± 14.1
	SB+	67 ± 31	0.5 ± 1.7	44 ± 6	8.6 ± 12.3
Interaction, region × ventilatory mode		ns	ns	ns	ns

Dependent and nondependent region of interest on transverse computed tomography scan (see Figure 1, center for details). SB-, airway pressure release ventilation without spontaneous breathing; SB+, airway pressure release ventilation with spontaneous breathing; ns, not significant.