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Changes in regional ventilation determined by volume and pressure-controlled ventilation as assessed by electrical impedance tomography in an experimental model of acid-induced acute lung injury

  • 1,
  • 1,
  • 1,
  • 1,
  • 1 and
  • 1
Critical Care201014 (Suppl 1) :P174

https://doi.org/10.1186/cc8406

  • Published:

Keywords

  • Acute Lung Injury
  • Electrical Impedance Tomography
  • Impedance Change
  • Intratracheal Instillation
  • Regional Ventilation

Introduction

Electrical impedance tomography (EIT) is a promising bedside tool for monitoring regional lung ventilation during mechanical ventilation [1]. The purpose of this study was to assess regional lung ventilation by EIT in a pig model of acid-induced acute lung injury (ALI) during pressure-controlled (PCV) and volume-controlled ventilation (VCV).

Methods

Ten anesthetized and tracheotomized female pigs (25 to 30 kg) were randomized into two groups: mechanical ventilation by PCV (pressure adjusted to achieve and maintain 8 ml/kg tidal volume, n = 5) or VCV (8 ml/kg, n = 5) in FiO2 50%. ALI was induced in both groups by intratracheal instillation of 4 ml/kg hydrochloric acid (HCl) 0.1 N. Impedance changes (Draeger, Germany) were recorded by a 16-electrode belt placed at the level of the sixth intercostal space, and four horizontal, equally-sized regions of interest (ROIs) were defined for offline data analysis. Measurements were performed before (T-BL) and after lung injury (T-ALI). Lung tidal volume (Vt), pulmonary static compliance (Cstat), pulmonary mean artery pressure (mPAP), peak pressure (Pp), respiratory rate (RR) and PaO2/FiO2 ratio were also recorded. Statistical analysis was based on two-way ANOVA followed by the Tukey test for analysis of data within and between groups, and a t test was used analysis of impedance changes induced by ALI.

Results

After ALI, both PCV and VCV groups showed significant decreases in the PaO2/FiO2 ratio (479.6 ± 46.5 to 244.5 ± 64.7 and 428.8 ± 22.9 to 212.4 ± 26.7) and Cstat (29.2 ± 5.1 to 13.2 ± 2.3 and 26.6 ± 3.4 to 12.3 ± 3.2) and significant increases in Pp (14.2 ± 1.9 to 25.6 ± 2.6 and 13.8 ± 0.8 to 24.6 ± 4.16) and mPAP (19.6 ± 0.5 to 35.2 ± 5.8 and 19.4 ± 1.5 to 26.8 ± 4.5). Between groups, only mPAP was statistically different at T-ALI. Global impedance decreased slightly after ALI in both groups, with no statistical significance. At T-ALI, there were statistically significant differences in tidal distributions of ROIs 2 (38.9 ± 2.6% to 42.4 ± 3.9%) and 3 (39.7 ± 3.1 to 35.1 ± 4.3%) of animals in the VCV group, when compared with T-BL. No significant difference was found in the PCV group.

Conclusions

EIT assessment of ventilation revealed a ventral shift in the tidal distribution in the VCV group after ALI, while PCV preserved tidal distribution observed at baseline.

Declarations

Acknowledgements

Grants from FAPESP (08/55376-7 and 08/56792-4) and LIM08/FMUSP.

Authors’ Affiliations

(1)
Universidade de São Paulo, Brazil

References

  1. Frerichs I, et al.: Physiol Meas. 2007, 28: S261-S267. 10.1088/0967-3334/28/7/S19PubMedView ArticleGoogle Scholar

Copyright

© BioMed Central Ltd. 2010

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