Positive end-expiratory pressure and variable ventilation in lung-healthy rats under general anesthesia.

Luciana M Camilo,Peter M Spieth,Walter A Zin,Marcelo Amato,Luis Felipe S Cruz,Alysson R Carvalho,Gabriel C M Ribeiro,Mariana B Ávila,Antonio Giannella-Neto,Andreas A Reske,Jorge If Salluh

doi:10.1371/journal.pone.0110817

Luciana M Camilo, Peter M Spieth + Show 9 more

Open Access

https://doi.org/10.1371/journal.pone.0110817

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Journal: PloS one	Publication Date: Nov 10, 2014
Citations: 47	License type: CC BY 4.0

Affiliation: TU Dresden, Universidade de São Paulo, Leipzig University

Abstract

ObjectivesVariable ventilation (VV) seems to improve respiratory function in acute lung injury and may be combined with positive end-expiratory pressure (PEEP) in order to protect the lungs even in healthy subjects. We hypothesized that VV in combination with moderate levels of PEEP reduce the deterioration of pulmonary function related to general anesthesia. Hence, we aimed at evaluating the alveolar stability and lung protection of the combination of VV at different PEEP levels.DesignRandomized experimental study.SettingAnimal research facility.SubjectsForty-nine male Wistar rats (200–270 g).InterventionsAnimals were ventilated during 2 hours with protective low tidal volume (VT) in volume control ventilation (VCV) or VV and PEEP adjusted at the level of minimum respiratory system elastance (Ers), obtained during a decremental PEEP trial subsequent to a recruitment maneuver, and 2 cmH2O above or below of this level.Measurements and Main ResultsErs, gas exchange and hemodynamic variables were measured. Cytokines were determined in lung homogenate and plasma samples and left lung was used for histologic analysis and diffuse alveolar damage scoring. A progressive time-dependent increase in Ers was observed independent on ventilatory mode or PEEP level. Despite of that, the rate of increase of Ers and lung tissue IL-1 beta concentration were significantly lower in VV than in VCV at the level of the PEEP of minimum Ers. A significant increase in lung tissue cytokines (IL-6, IL-1 beta, CINC-1 and TNF-alpha) as well as a ventral to dorsal and cranial to caudal reduction in aeration was observed in all ventilated rats with no significant differences among groups.ConclusionsVV combined with PEEP adjusted at the level of the PEEP of minimal Ers seemed to better prevent anesthesia-induced atelectasis and might improve lung protection throughout general anesthesia.

Highlights

Pulmonary atelectasis is a common complication during general anesthesia [1]
variable ventilation (VV) combined with positive end-expiratory pressure (PEEP) adjusted at the level of the PEEP of minimal Ers seemed to better prevent anesthesiainduced atelectasis and might improve lung protection throughout general anesthesia
Anesthesia-induced atelectasis causes an increase in intrapulmonary shunt [2] and highly correlates with the progressive reduction in lung compliance and oxygenation impairment throughout surgery [1,3]

Summary

Introduction

Pulmonary atelectasis is a common complication during general anesthesia [1]. Anesthesia-induced atelectasis causes an increase in intrapulmonary shunt [2] and highly correlates with the progressive reduction in lung compliance and oxygenation impairment throughout surgery [1,3]. Left ventricular compliance [11,12], cardiac output and systemic oxygen delivery [13,14], and still may result in lung overdistension with increased dead space ventilation and lung rupture [15,16,17,18]. In this line, the use of the so called open-lung PEEP [19] is still a challenge at the operating room routine [20,21]. The release of pro-inflammatory mediators (IL-6, IL-8, TNF-alpha) is significantly less in VV than in controlled ventilation [26,29,32]

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