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Extracorporeal life support (ECLS) is fast becoming more common place for use in adult patients failing mechanical ventilation. Management of coagulation and thrombosis has long been a major complication in the use of ECLS therapies. Scanning electron microscopy (SEM) of membrane oxygenators (MOs) after use in ECLS circuits can offer novel insight into any thrombotic material deposition on the MO. In this pilot study, we analyzed five explanted MOs immediately after use in a sheep model of different acute respiratory distress syndrome (ARDS). We describe our methods of MO dissection, sample preparation, image capture, and results. Of the five MOs analyzed, those that received continuous heparin infusion showed very little thrombosis formation or other clot material, whereas those that were used with only initial heparin bolus showed readily apparent thrombotic material.

OBJECTIVES: Venovenous extracorporeal gas exchange is increasingly used in awake, spontaneously breathing patients as a bridge to lung transplantation. Limited data are available on a similar use of extracorporeal gas exchange in patients with acute respiratory distress syndrome. The aim of this study was to investigate the use of extracorporeal gas exchange in awake, spontaneously breathing sheep with healthy lungs and with acute respiratory distress syndrome and describe the interactions between the native lung (healthy and diseased) and the artificial lung (extracorporeal gas exchange) in this setting. DESIGN: Laboratory investigation. SETTING: Animal ICU of a governmental laboratory. SUBJECTS: Eleven awake, spontaneously breathing sheep on extracorporeal gas exchange. INTERVENTIONS: Sheep were studied before (healthy lungs) and after the induction of acute respiratory distress syndrome via IV injection of oleic acid. Six gas flow settings (1-10 L/min), resulting in different amounts of extracorporeal CO2 removal (20-100% of total CO2 production), were tested in each animal before and after the injury. MEASUREMENTS AND MAIN RESULTS: Respiratory variables and gas exchange were measured for every gas flow setting. Both healthy and injured sheep reduced minute ventilation according to the amount of extracorporeal CO2 removal, up to complete apnea. However, compared with healthy sheep, sheep with acute respiratory distress syndrome presented significantly increased esophageal pressure variations (25 ± 9 vs 6 ± 3 cm H2O; p < 0.001), which could be reduced only with very high amounts of CO2 removal (> 80% of total CO2 production). CONCLUSIONS: Spontaneous ventilation of both healthy sheep and sheep with acute respiratory distress syndrome can be controlled via extracorporeal gas exchange. If this holds true in humans, extracorporeal gas exchange could be used in awake, spontaneously breathing patients with acute respiratory distress syndrome to support gas exchan

Introduction: The clinical use of serial quantitative computed tomography (CT) to characterize lung disease and guide the optimization of mechanical ventilation in patients with acute respiratory distress syndrome (ARDS) is limited by the risk of cumulative radiation exposure and by the difficulties and risks related to transferring patients to the CT room. We evaluated the effects of tube current-time product (mAs) variations on quantitative results in healthy lungs and in experimental ARDS in order to support the use of low-dose CT for quantitative analysis. Methods: In 14 sheep chest CT was performed at baseline and after the induction of ARDS via intravenous oleic acid injection. For each CT session, two consecutive scans were obtained applying two different mAs: 60 mAs was paired with 140, 15 or 7.5 mAs. All other CT parameters were kept unaltered (tube voltage 120 kVp, collimation 32x0.5 mm, pitch 0.85, matrix 512x512, pixel size 0.625x0.625 mm ). Quantitative results obtained at different mAs were compared via Bland-Altman analysis. Results: Good agreement was observed between 60 mAs and 140 mAs and between 60 mAs and 15 mAs (all biases less than 1%). A further reduction of mAs to 7.5 mAs caused an increase in the bias of poorly and non aerated tissue (-2.9 and 2.4%, respectively) and determined a significant widening of the limits of agreement for the same compartments (-10.5 - 4.8 % for poorly aerated and -5.9 - 10.8% for non aerated tissue). Estimated mean effective dose at 140, 60, 15 and 7.5 mAs corresponded to 17.8, 7.4, 2.0 and 0.9 millisievert, respectively. Image noise of scans performed at 140, 60, 15 and 7.5 mAs corresponded to 10, 16, 38 and 74 Hounsfield Units, respectively. Conclusions: A reduction of effective dose up to 70% has been achieved with minimal effects on lung quantitative results. Low-dose computed tomography provides accurate quantitative results and could be used to characterize lung compartment distribution and possibly monitor t

PURPOSE: Bicaval dual-lumen catheters allow for single-site cannulation venovenous extracorporeal gas exchange and facilitate early mobilization of patients. Using these catheters blood is drained from the superior and inferior venae cavae, pumped through a respiratory membrane, and returned into the right atrium. The insertion of these catheters is challenging as their correct positioning is fundamental to reduce recirculation and avoid severe complications. We describe here a new technique for the positioning of bicaval dual-lumen catheters. MATERIALS AND METHODS: The right internal jugular vein was percutaneously cannulated in nine sheep. The distance between skin and tricuspid valve was measured from the point of pressure change in the waveform of a Swan-Ganz catheter being retracted from the right ventricle into the right atrium. The atrium-tricuspid valve-ventricle axis was determined by observing the fluctuations of the tip of the Swan-Ganz entering the ventricle during fluoroscopy. A bicaval dual-lumen catheter was placed on the basis of these evaluations and connected to an extracorporeal respiratory support system. RESULTS: The position of the catheter was verified at necropsy approximately 18 h after insertion. In all cases the catheter was correctly placed, with the central port situated in front of the tricuspid valve. CONCLUSIONS: The described technique may help to position bicaval dual-lumen catheters for venovenous extracorporeal gas exchange without the use of transesophageal echocardiography or contrast media during fluoroscopy