The biological effects of higher and lower positive end-expiratory pressure in pulmonary and extrapulmonary acute lung injury with intra-abdominal hypertension.

Abstract

INTRODUCTION:

Mechanical ventilation with high positive end-expiratory pressure (PEEP) has been used in patients with acute respiratory distress syndrome (ARDS) and intra-abdominal hypertension (IAH), but the role of PEEP in minimizing lung injury remains controversial. We hypothesized that in the presence of acute lung injury (ALI) with IAH: 1) higher PEEP levels improve pulmonary morphofunction and minimize lung injury; and 2) the biological effects of higher PEEP are more effective in extrapulmonary (exp) than pulmonary (p) ALI.

METHODS:

In 48 adult male Wistar rats, ALIp and ALIexp were induced by Escherichia coli lipopolysaccharide intratracheally and intraperitoneally, respectively. After 24 hours, animals were anesthetized and mechanically ventilated (tidal volume of 6 mL/kg). IAH (15 mmHg) was induced and rats randomly assigned to PEEP of 5 (PEEP5), 7 (PEEP7) or 10 (PEEP10) cmH2O for 1 hour.

RESULTS:

In both ALIp and ALIexp, higher PEEP levels improved oxygenation. PEEP10 increased alveolar hyperinflation and epithelial cell damage compared to PEEP5, independent of ALI etiology. In ALIp, PEEP7 and PEEP10 increased lung elastance compared to PEEP5 (4.3 ± 0.7 and 4.3 ± 0.9 versus 3.1 ± 0.3 cmH2O/mL, respectively, P <0.01), without changes in alveolar collapse, interleukin-6, caspase-3, type III procollagen, receptor for advanced glycation end-products, and vascular cell adhesion molecule-1 expressions. Moreover, PEEP10 increased diaphragmatic injury compared to PEEP5. In ALIexp, PEEP7 decreased lung elastance and alveolar collapse compared to PEEP5 (2.3 ± 0.5 versus 3.6 ± 0.7 cmH2O/mL, P <0.02, and 27.2 (24.7 to 36.8) versus 44.2 (39.7 to 56.9)%, P <0.05, respectively), while PEEP7 and PEEP10 increased interleukin-6 and type III procollagen expressions, as well as type II epithelial cell damage compared to PEEP5.

CONCLUSIONS:

In the current models of ALI with IAH, in contrast to our primary hypothesis, higher PEEP is more effective in ALIp than ALIexp as demonstrated by the activation of biological markers. Therefore, higher PEEP should be used cautiously in the presence of IAH and ALI, mainly in ALIexp.

• Authors: Cíntia Lourenco Santos, Lillian Moraes, Raquel Souza Santos, Cynthia dos Santos Samary, Johnatas Dutra Silva, Marcelo Marcos Morales, Vera Lucia Capelozzi, Marcelo Gama de Abreu, Alberto Schanaider, Pedro Leme Silva, Cristiane Sousa Nascimento Baez Garcia, Paolo Pelosi, Patricia Rieken Macedo Rocco
• Journal: Critical care (London, England) (Crit Care) Vol. 18 Issue 3 Pg. R121 (Jun 13 2014) ISSN: 1466-609X [Electronic] England
• PMID: 24928415 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)

Chemical References

• Biomarkers

Topics

• Acute Lung Injury (complications, physiopathology, therapy)
• Animals
• Apoptosis
• Biomarkers (metabolism)
• Endothelium (pathology)
• Epithelium (pathology)
• Fibrosis (pathology)
• Inflammation (metabolism)
• Intra-Abdominal Hypertension (complications)
• Lung (pathology, physiopathology)
• Male
• Positive-Pressure Respiration
• Rats, Wistar