Intensive care medicine experimental
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Intensive Care Med Exp · Dec 2017
Optimal esophageal balloon volume for accurate estimation of pleural pressure at end-expiration and end-inspiration: an in vitro bench experiment.
Esophageal pressure, used as a surrogate for pleural pressure, is commonly measured by air-filled balloon, and the accuracy of measurement depends on the proper balloon volume. It has been found that larger filling volume is required at higher surrounding pressure. In the present study, we determined the balloon pressure-volume relationship in a bench model simulating the pleural cavity during controlled ventilation. The aim was to confirm whether an optimal balloon volume range existed that could provide accurate measurement at both end-expiration and end-inspiration. ⋯ In each of the tested balloon, an optimal filling volume range was found that provided accurate measurement during both end-expiratory and end-inspiratory occlusion.
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Intensive Care Med Exp · Dec 2017
Impact of membrane lung surface area and blood flow on extracorporeal CO2 removal during severe respiratory acidosis.
Veno-venous extracorporeal CO2 removal (vv-ECCO2R) is increasingly being used in the setting of acute respiratory failure. Blood flow rates through the device range from 200 ml/min to more than 1500 ml/min, and the membrane surface areas range from 0.35 to 1.3 m2. The present study in an animal model with similar CO2 production as an adult patient was aimed at determining the optimal membrane lung surface area and technical requirements for successful vv-ECCO2R. ⋯ In this porcine model, vv-ECCO2R was most effective when using blood flow rates ranging between 750 and 1000 ml/min, with a membrane lung surface of at least 0.8 m2. In contrast, low blood flow rates (250-500 ml/min) were not sufficient to completely correct severe respiratory acidosis, irrespective of the surface area of the membrane lung being used. The converse was also true, low surface membrane lungs (0.4 m2) were not capable of completely correcting severe respiratory acidosis across the range of blood flows used in this study.
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Intensive Care Med Exp · Dec 2017
Extracorporeal CO2 removal by hemodialysis: in vitro model and feasibility.
Critically ill patients with acute respiratory distress syndrome and acute exacerbations of chronic obstructive pulmonary disease often develop hypercapnia and require mechanical ventilation. Extracorporeal carbon dioxide removal can manage hypercarbia by removing carbon dioxide directly from the bloodstream. Respiratory hemodialysis uses traditional hemodialysis to remove CO2 from the blood, mainly as bicarbonate. In this study, Stewart's approach to acid-base chemistry was used to create a dialysate that would maintain blood pH while removing CO2 as well as determine the blood and dialysate flow rates necessary to remove clinically relevant CO2 volumes. ⋯ When the bench top data is scaled up, the system removes a therapeutic amount of CO2 standard intermittent hemodialysis flow rates. The zero bicarbonate dialysate did not cause acidosis in the post-dialyzer blood. These results demonstrate that, with further development, respiratory hemodialysis can be a minimally invasive extracorporeal carbon dioxide removal treatment option.
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Intensive Care Med Exp · Dec 2017
Proliferation and differentiation of adipose tissue in prolonged lean and obese critically ill patients.
In prolonged non-obese critically ill patients, preservation of adipose tissue is prioritized over that of the skeletal muscle and coincides with increased adipogenesis. However, we recently demonstrated that in obese critically ill mice, this priority was switched. In the obese, the use of abundantly available adipose tissue-derived energy substrates was preferred and counteracted muscle wasting. These observations suggest that different processes are ongoing in adipose tissue of lean vs. overweight/obese critically ill patients. ⋯ Contrary to what was hypothesized, adipogenesis increased independently of initial BMI in prolonged critically ill patients. Not the production of local eicosanoid PPARγ agonists but circulating adipogenic factors seem to be involved in critical illness-induced adipogenesis. Importantly, our findings suggest that abundantly available energy substrates from the adipose tissue, rather than excess adipocytes, can play a beneficial role during critical illness.
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Intensive Care Med Exp · Dec 2017
Hyperoxia provokes a time- and dose-dependent inflammatory response in mechanically ventilated mice, irrespective of tidal volumes.
Mechanical ventilation and hyperoxia have the potential to independently promote lung injury and inflammation. Our purpose was to study both time- and dose-dependent effects of supplemental oxygen in an experimental model of mechanically ventilated mice. ⋯ We demonstrated a severe vascular leakage and a pro-inflammatory pulmonary response in mechanically ventilated mice, which was enhanced by severe hyperoxia and longer duration of mechanical ventilation. Prolonged ventilation with high oxygen concentrations induced a time-dependent immune response characterized by elevated levels of neutrophils, cytokines, and chemokines in the pulmonary compartment.