Abstract
BackgroundOscillations of the arterial partial pressure of oxygen induced by varying shunt fractions occur during cyclic alveolar recruitment within the injured lung. Recently, these were proposed as a pathomechanism that may be relevant for remote organ injury following acute respiratory distress syndrome. This study examines the transmission of oxygen oscillations to the renal tissue and their tidal volume dependency.MethodsLung injury was induced by repetitive bronchoalveolar lavage in eight anaesthetized pigs. Cyclic alveolar recruitment was provoked by high tidal volume ventilation. Oscillations of the arterial partial pressure of oxygen were measured in real-time in the macrocirculation by multi-frequency phase fluorimetry and in the renal microcirculation by combined white-light spectrometry and laser-Doppler flowmetry during tidal volume down-titration.ResultsSignificant respiratory-dependent oxygen oscillations were detected in the macrocirculation and transmitted to the renal microcirculation in a substantial extent. The amplitudes of these oscillations significantly correlate to the applied tidal volume and are minimized during down-titration.ConclusionsIn a porcine model oscillations of the arterial partial pressure of oxygen are induced by cyclic alveolar recruitment and transmitted to the renal microcirculation in a tidal volume-dependent fashion. They might play a role in organ crosstalk and remote organ damage following lung injury.
Highlights
Oscillations of the arterial partial pressure of oxygen induced by varying shunt fractions occur during cyclic alveolar recruitment within the injured lung
The animals were ventilated using a volume-controlled mode (AVEA, Carefusion, San Diego, USA) with a tidal volume of 7 ml/kg, positive endexpiratory pressure (PEEP) of 5 mbar, fraction of inspired oxygen (FiO2) of 0.4 and respiratory rate oriented on the end-tidal CO2
The alveolar lavage created significant acute lung injury as demonstrated by the Arterial oxygen partial pressure (PaO2)/Fraction of inspired oxygen (FiO2) ratio dropping from 505 ± 49 to 202 ± 90 mmHg
Summary
Oscillations of the arterial partial pressure of oxygen induced by varying shunt fractions occur during cyclic alveolar recruitment within the injured lung. These were proposed as a pathomechanism that may be relevant for remote organ injury following acute respiratory distress syndrome. Especially acute respiratory distress syndrome (ARDS) and acute kidney injury, can be caused by the same external etiology, and trigger each other. The combination of both is linked to prolonged intensive care stays and increased mortality [2,3,4]. The role of the tidal volume as driving force for PaO2 oscillations, their transmission to various distant organ microcirculatory sites and the kidney is yet unknown
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