0893. High respiratory rate favors pulmonary edema in an experimental model of acute lung injury
https://doi.org/10.1186/2197-425X-2-S1-O19
© Retamal et al; licensee Springer. 2014
Published: 26 September 2014
Keywords
Introduction
The ARDS-net protocol [1], recommends that respiratory rate (RR) could be increased at hypercapnia in order to normalize PaCO2. However, i n heterogeneously inflated lungs, e.g., ARDS, at every breath the local alveolar distending forces will be amplified up to 4.5 times in the interphase between collapsed and aerated areas [2]. Thus, a higher RR could exaggerate the cyclic deformations of lung parenchyma and might therefore induce further lung injury. Indeed, animal studies using simultaneous modifications of flow and tidal volume have indicated that low respiratory rates are lung protective [3]. We therefore hypothesized that an isolated increase of RR would augment the development of ventilator induced lung injury (VILI).
Objectives
To compare VILI development at two clinically relevant RR during protective mechanical ventilation setting, keeping constant flow, tidal volume (VT) and pCO2 levels.
Methods
Healthy piglets were subjected to a two-hit lung injury model (saline lavages followed by 2 hours of injurious ventilation), and then randomized into two groups: LRR 20 breaths/min (n=6), and HRR 40 breaths/min (n=6), and were mechanically ventilated during six hours according to ARDSnet protocol (VT 6 ml/kg, PEEP10 cmH2O, FiO2 0.5), keeping an inspiratory time of 0.5 sec. We used instrumental dead space to keep similar values of pCO2 in both groups. We assessed respiratory mechanics, invasive systemic and pulmonary arterial pressures, volumetric capnography and extravascular lung water (EVLW). At the end of the experiments lungs were excised and wet/dry (W/D) ratio was evaluated.
Results
Dynamic compliance
Extravascular lung water (EVLW)
Wet/Dry weight ratio
Conclusions
In our study high respiratory rate reduced lung water clearance, which resulted in an increase of lung water content, indicating that increasing respiratory rate could augment VILI.
Declarations
Grant acknowledgment
Beca Cotutela Doctoral CONICYT.
Authors’ Affiliations
References
- ARDSNet: Ventilation with lower tidal volumes as compared with traditional tidal volumes for acute lung injury and the acute respiratory distress syndrome. N Engl J Med 2000, 342: 1301–1308.View ArticleGoogle Scholar
- Mead J: Stress distribution in lungs: a model of pulmonary elasticity. J Appl Physiol 1979, 28: 596–608.Google Scholar
- Vaporidi K: Effects of respiratory rate on ventilator-induced lung injury at a constant PaCO2 in a mouse model of normal lung. Crit Care Med 2008,36(4):1277–1283.PubMedView ArticleGoogle Scholar
Copyright
This article is published under license to BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.