Tidal volume delivered by mechanical ventilation to a sedated patient is distributed in a non-physiological pattern, causing atelectasis (underinflation) and overdistension (overinflation). Activation of the diaphragm during mechanical ventilation provides a way to reduce atelectasis and alveolar inhomogeneity, protecting the lungs from ventilator-induced lung injury while also protecting the diaphragm by preventing ventilator-induced diaphragm dysfunction. We studied the hypothesis that diaphragm contractions elicited by transvenous phrenic nerve stimulation, delivered in synchrony with volume-control ventilation, would reduce atelectasis and lung inhomogeneity in a healthy, normal-lung pig model. Twenty-five large pigs were ventilated for 50 hours with lung-protective volume-control ventilation combined with synchronous transvenous phrenic-nerve neurostimulation on every breath, or every second breath. This was compared to lung-protective ventilation alone. Lung mechanics and ventilation pressures were measured using esophageal pressure manometry and electrical impedance tomography. Alveolar homogeneity was measured using alveolar chord length of preserved lung tissue. Lung injury was measured using inflammatory cytokine concentration in bronchoalveolar lavage fluid and serum. We found that diaphragm neurostimulation on every breath preserved PaO2/FiO2 and significantly reduced the loss of end-expiratory lung volume after 50 hours of mechanical ventilation. Neurostimulation on every breath reduced plateau and driving pressures, improved both static and dynamic compliance and resulted in less alveolar inhomogeneity. These findings support that temporary transvenous diaphragm neurostimulation during volume-controlled, lung-protective ventilation may offer a potential method to provide both lung- and diaphragm-protective ventilation.
Increased lung heterogeneity from regional alveolar collapse drives ventilator-induced lung injury in ARDS patients. New methods of preventing this injury require study. Our study objective was to determine whether the combination of temporary transvenous diaphragm neurostimulation with standard-of-care volume-control mode ventilation changes lung mechanics, reducing ventilator-induced lung injury risk in a preclinical ARDS model. Moderate ARDS was induced using oleic acid administered into the pulmonary artery in pigs, which were ventilated for 12 hours post-injury using volume-control mode at 8 ml/kg, PEEP 5 cmH2O, with respiratory rate and FiO2 set to achieve normal arterial blood gases. Two groups received TTDN, either every second breath (MV+TTDN50%, n=6) or every breath (MV+TTDN100%, n=6). A third group received volume-control ventilation only (MV, n=6). At study-end, PaO2/FiO2 was highest and alveolar-arterial oxygen gradient was lowest for MV+TTDN100% (p<0.05). MV+TTDN100% had the smallest end-expiratory lung volume loss and lowest extravascular lung water at study-end (p<0.05). Static lung compliance was highest and transpulmonary driving pressure was lowest at baseline, post-injury, and study-end in MV+TTDN100% (p<0.05). The total exposure to transpulmonary driving pressure, mechanical power and mechanical work was the lowest in MV+TTDN100% (p<0.05). Lung injury score and total inflammatory cytokine concentration in lung tissue were the lowest in MV+TTDN100% (p<0.05). Volume-control ventilation plus transvenous diaphragm neurostimulation on every breath improved PaO2/FiO2, A-a gradient and alveolar homogeneity, as well as reduced driving pressure, mechanical power, and mechanical work, and resulted in lower lung injury scores and tissue cytokine concentrations in a preclinical ARDS model.
In 2018, 47 % of global internet users had purchased footwear products through the internet, making it the second most popular online shopping category worldwide right after clothing with 57 %. In the same year, on average, about every sixth parcel delivered in Germany (16.3 %) was returned. With the effort and costs that are associated with the return of shoes, the objective of reducing the number of returns for shoes promises an enormous economic potential and helps to reduce the CO2 emissions due to a lower trafic volume. This paper presents a workflow for determining the inside volume surface of shoes using industrial X-ray computed tomography (CT). The fundamental idea is based on the Region Growing (RG) method for the segmentation of the shoe's inner volume. Experiments are performed to illustrate the correlation of image quality and segmentation result. After obtaining the 3D surface model of an individual foot, the inner volume surface data of a scanned shoe can then be registered and evaluated in order to provide a reliable feedback for the customer regarding the accuracy of fit of a shoe and the individual foot on the basis of an overall "metric of comfort" before buying online. This step is not part of the work at hand. Conclusions are drawn and suggestions for improving the robustness and the exibility of the workflow are given, so it can be adapted to various shoe types and implemented in a fully automated measurement process in the future.
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