High respiratory rate is associated with early reduction of lung edema clearance in an experimental model of ARDS.

Abstract

BACKGROUND:

The independent impact of respiratory rate on ventilator-induced lung injury has not been fully elucidated. The aim of this study was to investigate the effects of two clinically relevant respiratory rates on early ventilator-induced lung injury evolution and lung edema during the protective ARDSNet strategy. We hypothesized that the use of a higher respiratory rate during a protective ARDSNet ventilation strategy increases lung inflammation and, in addition, lung edema associated to strain-induced activation of transforming growth factor beta (TGF-β) in the lung epithelium.

METHODS:

Twelve healthy piglets were submitted to a two-hit lung injury model and randomized into two groups: LRR (20 breaths/min) and HRR (40 breaths/min). They were mechanically ventilated during 6 h according to the ARDSNet strategy. We assessed respiratory mechanics, hemodynamics, and extravascular lung water (EVLW). At the end of the experiment, the lungs were excised and wet/dry ratio, TGF-β pathway markers, regional histology, and cytokines were evaluated.

RESULTS:

No differences in oxygenation, PaCO2 levels, systemic and pulmonary arterial pressures were observed during the study. Respiratory system compliance and mean airway pressure were lower in LRR group. A decrease in EVLW over time occurred only in the LRR group (P < 0.05). Wet/dry ratio was higher in the HRR group (P < 0.05), as well as TGF-β pathway activation. Histological findings suggestive of inflammation and inflammatory tissue cytokines were higher in LRR.

CONCLUSION:

HRR was associated with more pulmonary edema and higher activation of the TGF-β pathway. In contrast with our hypothesis, HRR was associated with less lung inflammation.

• Authors: J Retamal, J B Borges, A Bruhn, X Cao, R Feinstein, G Hedenstierna, S Johansson, F Suarez-Sipmann, A Larsson
• Journal: Acta anaesthesiologica Scandinavica (Acta Anaesthesiol Scand) Vol. 60 Issue 1 Pg. 79-92 (Jan 2016) ISSN: 1399-6576 [Electronic] England
• PMID: 26256848 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)
• Copyright: © 2015 The Acta Anaesthesiologica Scandinavica Foundation. Published by John Wiley & Sons Ltd.

Chemical References

• Cytokines
• Transforming Growth Factor beta

Topics

• Animals
• Arterial Pressure
• Bronchoalveolar Lavage Fluid
• Cytokines (analysis, metabolism)
• Extravascular Lung Water
• Hemodynamics
• Humans
• Organ Size
• Pulmonary Edema (physiopathology, therapy)
• Respiration, Artificial
• Respiratory Distress Syndrome (physiopathology, therapy)
• Respiratory Mucosa (metabolism)
• Respiratory Rate
• Sus scrofa
• Swine
• Transforming Growth Factor beta (metabolism)