Lung anatomy, energy load, and ventilator-induced lung injury

Intensive Care Medicine Experimental

Table 4 Respiratory mechanics in pigs grouped according to tidal volume

	Tidal volume below the lower limit of normal inspiratory capacity			Tidal volume above the lower limit of normal inspiratory capacity
	Alive	Dead	P	Alive	Dead	P
No.	40	7	P	9	20	P
Tidal volume (mL/kg)	16.0 [13.0–23.5]	16.7 [10.0–21.1]	0.591	34.7 [32.5–38.6]	37.0 [35.6–46.3]	0.045
PEEP (cmH₂O)	5 [0–10]	20 [6–26]	0.010	4 [0–5]	0 [0–6]	0.698
PEEP/ZEEP	24/16	6/1	0.165	5/4	8/12	0.436
Inspiratory volume (mL/kg)	23.8 [16.5–43.3]	48.9 [37.8–55.3]	0.009	41.1 [34.7–47.8]	46.3 [36.8–62.8]	0.334
Global strain	1.74 [0.90–2.21]	2.82 [2.44–4.18]	<0.001	2.34 [2.02–2.44]	2.64 [2.21–3.17]	0.085
Dynamic strain	0.87 [0.65–1.34]	0.97 [0.73–1.40]	0.630	1.93 [1.84–2.02]	2.34 [1.98–2.58]	0.005
Static strain	0.00 [0.00–1.15]	2.18 [1.11–2.97]	0.005	0.48 [0.00–0.63]	0.00 [0.00–0.72]	0.698
FRC (mL)	397 ± 102	361 ± 73	0.370	387 ± 78	382 ± 91	0.880

Mean ± standard deviations or median (interquartile range) or occurrences of respiratory mechanics variables in pigs grouped according to their tidal volume (not end-inspiratory volume) in relation to normal inspiratory capacity (below or above the lower limit). Pigs were then grouped according to outcome. P refers to paired t test or Wilcoxon’s Signed Rank Test, as appropriate, for continuous variables and the chi-square test for categorical variables
PEEP indicates positive end-expiratory pressure, ZEEP indicates zero end-expiratory pressure, FRC indicates functional residual capacity