Intensive care medicine experimental
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Intensive Care Med Exp · Dec 2017
ReviewPersonalizing mechanical ventilation according to physiologic parameters to stabilize alveoli and minimize ventilator induced lung injury (VILI).
It has been shown that mechanical ventilation in patients with, or at high-risk for, the development of acute respiratory distress syndrome (ARDS) can be a double-edged sword. If the mechanical breath is improperly set, it can amplify the lung injury associated with ARDS, causing a secondary ventilator-induced lung injury (VILI). Conversely, the mechanical breath can be adjusted to minimize VILI, which can reduce ARDS mortality. ⋯ Multiple methods of personalizing PEEP have been tested and include dead space, lung compliance, lung stress and strain, ventilation patterns using computed tomography (CT) or electrical impedance tomography (EIT), inflection points on the pressure/volume curve (P/V), and the slope of the expiratory flow curve using airway pressure release ventilation (APRV). Although many studies have shown that personalizing PEEP is possible, there is no consensus as to the optimal technique. This review will assess various methods used to personalize PEEP, directed by physiologic parameters, necessary to adaptively adjust ventilator settings with progressive changes in lung pathophysiology.
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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
Myocardial oxidative stress correlates with left ventricular dysfunction on strain echocardiography in a rodent model of sepsis.
Recognition of cardiomyopathy in sepsis can be challenging due to the limitations of conventional measures such as ejection fraction (EF) and fractional shortening (FS) in the context of variable preload and afterload conditions. This study correlates myocardial function using strain echocardiography (SE) with cardiomyocyte oxidative stress in a murine model of sepsis. ⋯ In this sepsis model, SE identified cardiomyopathy despite normal EF. SE depression temporally coincides with upregulation of inflammatory cytokines and decreases expression of key mitochondrial ROS scavengers. Upregulation of redox scavenger (CAT) abrogates oxidative stress and cardiac dysfunction in this sepsis model.
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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
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.