844 research outputs found
Cardiac-related impedance changes obtained by electrical impedance tomography: an acceptable parameter for assessment of pulmonary perfusion?
No full textComment on Borges et al. "Regional lung perfusion estimated by electrical impedance tomography in a piglet model of lung collapse"
No full textLung impedance measurements to monitor alveolar ventilation
No full textPurpose of review Electrical impedance tomography (EIT) is an attractive method of monitoring patients during mechanical ventilation because it can provide a noninvasive continuous image of pulmonary impedance, which indicates the distribution of ventilation. This article will discuss ongoing research on EIT, with a focus on methodological aspects and limitations and novel approaches in terms of pathophysiology, diagnosis and therapeutic advancements. Recent findings EIT enables the detection of regional distribution of alveolar ventilation and, thus, the quantification of local inhomogeneities in lung mechanics. By detecting recruitment and derecruitment, a positive end-expiratory pressure level at which tidal ventilation is relatively homogeneous in all lung regions can be defined. Additionally, different approaches to characterize the temporal local behaviour of lung tissue during ventilation have been proposed, which adds important information. Summary There is growing evidence that supports EIT usage as a bedside measure to individually optimize ventilator settings in critically ill patients in order to prevent ventilator-induced lung injury. A standardization of current approaches to analyse and interpret EIT data is required in order to facilitate the clinical implementation
Monitoring of Regional Lung Ventilation Using Electrical Impedance Tomography After Cardiac Surgery in Infants and Children
No full textElectrical impedance tomography (EIT) is a noninvasive method to monitor regional lung ventilation in infants and children without using radiation. The objective of this prospective study was to determine the value of EIT as an additional monitoring tool to assess regional lung ventilation after pediatric cardiac surgery for congenital heart disease in infants and children. EIT monitoring was performed in a prospective study comprising 30 pediatric patients who were mechanically ventilated after cardiac surgery. Data were analyzed off-line with respect to regional lung ventilation in different clinical situations. EIT data were correlated with respirator settings and arterial carbon dioxide (CO2) partial pressure in the blood. In 29 of 30 patients, regional ventilation of the lung could sufficiently and reliably be monitored by means of EIT. The effects of the transition from mechanical ventilation to spontaneous breathing after extubation on regional lung ventilation were studied. After extubation, a significant decrease of relative impedance changes was evident. In addition, a negative correlation of arterial CO2 partial pressure and relative impedance changes could be shown. EIT was sufficient to discriminate differences of regional lung ventilation in children and adolescents after cardiac surgery. EIT reliably provided additional information on regional lung ventilation in children after cardiac surgery. Neither chest tubes nor pacemaker wires nor the intensive care unit environment interfered with the application of EIT. EIT therefore may be used as an additional real-time monitoring tool in pediatric cardiac intensive care because it is noninvasive
Electrical impedance tomography is able to track changes in respiratory function in endotoxin-challenged rodents
No full textBackground and objective: In order to assess and optimize the effect of new therapies for acute lung injury (ALI) in rodent models, a monitoring technique that continuously assesses the functional state of the lung is mandatory. Electrical impedance tomography (EIT) has been suggested as a technique for quantifying lung inflammation in ALI. However, EIT has not been evaluated in a rodent model of ALI. Methods: EIT measurements were compared in ventilated Sprague-Dawley rats (n = 14), randomly subjected to intratracheal administration of endotoxin (LPS) or saline (control). Lung mechanics, lung weight wet/dry ratio and inflammatory markers in bronchoalveolar lavage fluid were also evaluated. Results: LPS caused a significant decrease in lung compliance and TLC as compared with control (-42.0%, P = 0.04, and -27.9%, P = 0.02, respectively). These changes were paralleled by differences in mean impedance changes as detected by EIT (Spearman's rank correlation coefficient: rho = 0.66 and 0.73, respectively, P < 0.01). LPS increased the lung weight wet/dry ratio (6.35 +/- 0.42 vs 5.15 +/- 0.07, P = 0.003), and the bronchoalveolar lavage total WCC (8.96 +/- 1.87 vs 1.16 +/- 0.10 x 10(9)/L, P = 0.002) as compared with control. The lung weight wet/dry ratio was inversely related to the mean impedance change (rho = -0.76, P < 0.01). Conclusions: This study has demonstrated for the first time that eight-electrode EIT readily tracks the inflammatory response of lung tissue in a rodent model of ALI. EIT may thus provide a promising, non-invasive technique for monitoring the time-course of ALI in rodent models, and for testing novel pharmacological strategies to counter it
The influence of callus distraction on the growth plate
No full textObjectives This study was designed to investigate the morphology, thickness and cellularity of the growth plate during callus distraction performed in the immediate vicinity of the growth plate. Methods Lengthening of the right tibia by 25% was carried out on 24 beagle dogs by callus distraction. Distraction was started at the fifth postoperative day with a distraction rate of 0.5 mm twice a day. A control group of six dogs underwent tibial osteotomy and external fixation without distraction. Half of the dogs of both groups were sacrificed at the end of the distraction phase of 25 days (Group A) and the remaining 15 dogs after an additional consolidation period of 25 days (Group B). The tibia and femur was removed from the distracted right leg and from the left control side of each animal and longitudinal sections were cut and stained with Pentachrome. The thickness and cellularity of the regeneration zone, the proliferation zone and the hypertrophic zone were determined for the proximal tibial and the distal femoral epiphysis. Results During the distraction phase the thickness of the proximal tibial growth plate and its cellularity were reduced on the distraction side. During the consolidation phase there was a slight recovery in the proximal tibial growth plate. Conclusions Callus distraction leads to a temporary reduction in growth of the affected physis
Short text authorship attribution via sequence kernels, Markov chains and author unmasking: An investigation
No full textWe present an investigation of recently proposed character and word sequence kernels for the task of authorship attribution based on relatively short texts. Performance is compared with two corresponding probabilistic approaches based on Markov chains. Several configurations of the sequence kernels are studied on a relatively large dataset (50 authors), where each author covered several topics. Utilising Moffat smoothing, the two probabilistic approaches obtain similar performance, which in turn is comparable to that of character sequence kernels and is better than that of word sequence kernels. The results further suggest that when using a realistic setup that takes into account the case of texts which are not written by any hypothesised authors, the amount of training material has more influence on discrimination performance than the amount of test material. Moreover, we show that the recently proposed author unmasking approach is less useful when dealing with short texts
Short Text Authorship Attribution via Sequence Kernels, Markov Chains and Author Unmasking: An Investigation
No full textWe present an investigation of recently proposed character and word sequence kernels for the task of authorship attribution based on relatively short texts. Performance is compared with two corresponding probabilistic approaches based on Markov chains. Several configurations of the sequence kernels are studied on a relatively large dataset (50 authors), where each author covered several topics. Utilising Moffat smoothing, the two probabilistic approaches obtain similar performance, which in turn is comparable to that of character sequence kernels and is better than that of word sequence kernels. The results further suggest that when using a realistic setup that takes into account the case of texts which are not written by any hypothesised authors, the amount of training material has more influence on discrimination performance than the amount of test material. Moreover, we show that the recently proposed author unmasking approach is less useful when dealing with short texts.
Short text authorship attribution via sequence kernels, Markov chains and author unmasking: An investigation
No full textWe present an investigation of recently proposed character and word sequence kernels for the task of authorship attribution based on relatively short texts. Performance is compared with two corresponding probabilistic approaches based on Markov chains. Several configurations of the sequence kernels are studied on a relatively large dataset (50 authors), where each author covered several topics. Utilising Moffat smoothing, the two probabilistic approaches obtain similar performance, which in turn is comparable to that of character sequence kernels and is better than that of word sequence kernels. The results further suggest that when using a realistic setup that takes into account the case of texts which are not written by any hypothesised authors, the amount of training material has more influence on discrimination performance than the amount of test material. Moreover, we show that the recently proposed author unmasking approach is less useful when dealing with short texts
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