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Critical Care

Open Access

Protective ventilation reduces bacterial growth and lung injury in a porcine pneumonia model

  • J Sperber1,
  • A Nyberg1,
  • M Lipcsey1,
  • A Larsson2,
  • J Sjolin2 and
  • M Castegren1
Critical Care201418(Suppl 1):P275

Published: 17 March 2014


Bacterial pneumonia is a common indication for mechanical ventilation in the ICU. Ventilation with high positive end- expiratory pressure (PEEP) and low tidal volume (VT) is recommended in patients with adult respiratory distress syndrome. This improves clinical outcome compared with ventilation with low PEEP and medium-high VT [1]. However, the effect of VT and PEEP on bacterial growth in lung tissue is not known. This study contrasted the effect of a protective ventilator protocol with a standard medium-high VT and lower PEEP protocol on lung bacterial growth, lung edema formation and lung injury. It was performed in a porcine model of intensive care with the frequently found pathogen Pseudomonas aeruginosa.


Sixteen pigs were anesthetized and randomized to mechanical ventilation with two different ventilator settings for 6 hours; Prot-V (PEEP 10 cmH2O, VT 6 ml/kg, n = 8) and Control (PEEP 5 cmH2O, VT 10 ml/kg, n = 8). At 0 hours, 1 × 1011 colony-forming units (cfu) of P. aeruginosa were instilled intratracheally. At the end of the experiment, six postmortem lung biopsies from predefined declivial locations were taken from each animal for cultures and weight measurements.


P. aeruginosa growth in lung tissue and wet to dry ratio were lower in the Prot-V group than in the Control group (P < 0.05 and P < 0.05). PaO2/FiO2 was higher in the Prot-V group than in the Control group (P < 0.05) (Table 1).
Table 1

P. aeruginosa log mean,wet to dry ratio, and PaO2/ FiO2at 5 hours


P. aeruginosa(cfu/g)


PaO2//FiO2 at 5 hours (mmHg)


3.5 ± 0.7

1.7 ± 0.2

434 ± 62


4.2 ± 0.7

2.7 ± 1.3

343 ± 61

Data presented as mean ± SD.


Protective ventilation with low VT and higher PEEP reduces P. aeruginosa growth in lung tissue, lung edema formation and lung injury in contrast with medium-high VT and lower PEEP ventilation in this porcine pneumonia model.

Authors’ Affiliations

Centre for Clinical Research Sormland, Uppsala University, Uppsala, Sweden
Uppsala University, Uppsala, Sweden


  1. N Engl J Med. 2000, 342: 1301-1308.Google Scholar


© Sperber et al.; licensee BioMed Central Ltd. 2014

This article is published under license to BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. The Creative Commons Public Domain Dedication waiver ( applies to the data made available in this article, unless otherwise stated.