High positive end-expiratory pressure: only a dam against oedema formation?

Table 2 Lung histology

	Present study	Previous study	P
Emphysematous changes	2 (2-3)	2 (2-3)	1.00
Interstitial congestion	2 (1-2)	2 (1-2)	0.23
Alveolar haemorrhage	1 (1-1)	1 (0-1)	0.60
Alveolar neutrophil infiltration	2 (2-2)	2 (1-3)	1.00
Alveolar macrophage proliferation	3 (2-3)	2 (1-2)	0.23
Alveolar type II pneumocytes proliferation	2 (2-2)	2 (2-2)	0.95
Interstitial lymphocytes proliferation	2 (1-2)	2 (1-2)	0.82
Interstitial thickening	2 (1-2)	2 (2-3)	0.05
Hyaline membranes formation	0 (0-0)	0 (0-1)	0.17
Interstitial fibrosis	1 (1-1)	2 (1-3)	0.02
Organization of alveolar exudate	1 (1-2)	1 (0-1)	0.19
Total score	18 (14-18)	18 (16-19)	0.43

Results of animals ventilated with high PEEP and low V_T for 36 h and with no PEEP and low V_T for 18 h (n = 5) (present study) were compared with those of animals ventilated with no PEEP and low V_T for 54 h (n = 12) (previous study) [3]. Alterations were graded from 0 to 4, with higher scores indicating more severe and diffuse abnormalities. Total score was the sum of all individual scores. P values refer to Mann-Whitney rank sum test. PEEP, positive end-expiratory pressure; V_T, tidal volume.

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