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

Abstract

IntroductionMechanical 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.MethodsIn 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.ResultsIn 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.ConclusionsIn 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.

Comparison of different degrees of variability in tidal volume to prevent deterioration of respiratory system elastance in experimental acute lung inflammation

“…Furthermore, data from our laboratory have shown that the acute lung inflammation induced by i.t. instillation of LPS responds to lung recruitment manoeuvres [10][11][12] and to different mechanical ventilation settings. 13 Gene expression of amphiregulin is closely related to mechanical cell stress and is not influenced by inflammation, 14 and IL-6, CINC-1, and TNF-α were chosen because they reflect inflammation during ventilator-induced lung injury.…”

Effect of protective lung ventilation strategy combined with lung recruitment maneuver in patients with acute respiratory distress syndrome (ARDS)

“…In addition, with the increasing understanding of pathophysiological mechanisms of ARDS, the researchers have found that different types of ARDS patients have different response to mechanical ventilation and drug intervention. At present, one universal classification is to divide the ARDS into pulmonary ARDS and extrapulmonary ARDS [24]. The main pathological mechanism of pulmonary ARDS is primary alveolar damage; and the main mechanism of extrapulmonary ARDS is the pulmonary capillary endothelial injury caused by extrapulmonary factors [25,26].…”

Early impact of abdominal compartment syndrome on liver, kidney and lung damage in a rodent model

“…In the present study, IAH was induced by packing the four quadrants of the peritoneal cavity with saline-soaked gauze dressings and closing both layers of the abdominal cavity until an IAP of 15 mm Hg was achieved [17]. This technique has some advantages over existing models.…”