594 research outputs found
Home based rehabilitation for patients with COPD:Is it equally effective as compared to outpatient rehabilitation?
Modelling selective activation of small myelinated nerve fibres using a monopolar point electrode
The aim of this study is to investigate theoretically the possibility for activation of small myelinated nerve fibres without activating larger ones when stimulating a nerve fibre bundle using a monopolar point electrode. Therefore, the sensitivity of excitation and blocking threshold currents of nerve fibres to fibre diameter, electrode-fibre distance and pulse duration has been simulated by a computer model. A simple infinite, homogeneous volume conductor and a cathodal point source were used in combination with a model representing the electrical properties of a myelinated nerve fibre. The results show that selective activation of small myelinated fibres may be possible in a region at some distance from the electrode
Home based rehabilitation for patients with COPD:Is it equally effective as compared to outpatient rehabilitation?
Exploiting flow dynamics for super-resolution in contrast-enhanced ultrasound
Ultrasound localization microscopy offers new radiation-free diagnostic tools
for vascular imaging deep within the tissue. Sequential localization of echoes
returned from inert microbubbles with low-concentration within the bloodstream
reveal the vasculature with capillary resolution. Despite its high spatial
resolution, low microbubble concentrations dictate the acquisition of tens of
thousands of images, over the course of several seconds to tens of seconds, to
produce a single super-resolved image. %since each echo is required to be well
separated from adjacent microbubbles. Such long acquisition times and stringent
constraints on microbubble concentration are undesirable in many clinical
scenarios. To address these restrictions, sparsity-based approaches have
recently been developed. These methods reduce the total acquisition time
dramatically, while maintaining good spatial resolution in settings with
considerable microbubble overlap. %Yet, non of the reported methods exploit the
fact that microbubbles actually flow within the bloodstream. % to improve
recovery. Here, we further improve sparsity-based super-resolution ultrasound
imaging by exploiting the inherent flow of microbubbles and utilize their
motion kinematics. While doing so, we also provide quantitative measurements of
microbubble velocities. Our method relies on simultaneous tracking and
super-localization of individual microbubbles in a frame-by-frame manner, and
as such, may be suitable for real-time implementation. We demonstrate the
effectiveness of the proposed approach on both simulations and {\it in-vivo}
contrast enhanced human prostate scans, acquired with a clinically approved
scanner.Comment: 11 pages, 9 figure
Upper airway pressure distribution during nasal high-flow therapy
Two working mechanisms of Nasal High-Flow Therapy (NHFT) are washout of anatomical dead space and provision of positive end-expiratory pressure (PEEP). The extent of both mechanisms depends on the respiration aerodynamics and the corresponding pressure distribution: at end-expiration the onset of uniform pressure indicates the jet penetration length, and the level of the uniform pressure is the PEEP. The clinical problem is that adequate measurements in patients are presently impossible. In this study, the respiratory pressure distribution is therefore measured in 3D-printed anatomically correct upper-airway models of an adult and an infant. Assuming that elastic fluctuations in airway anatomy are sufficiently small, the aerodynamics in these rigid models will be very similar to the aerodynamics in patients. It appears that, at end-expiration, the jet penetrates into or slightly beyond the nasal cavity, hardly depending on cannula size or NHFT flow rate. PEEP is approximately proportional to the square of the flow rate: it can be doubled by increasing the flow rate by 40%. In the adult model, PEEP is accurately predicted by the dynamic pressure at the prong-exits, but in the infant model this method fails. During respiration, large pressure fluctuations occur when the cannula is relatively large compared to the nostrils
Effects of non-invasive positive pressure ventilation (NIPPV) in stable chronic obstructive pulmonary disease (COPD)
This review provides an overview of the randomised controlled trials covering the topic of chronic non-invasive positive pressure ventilation (NIPPV) in severe stable COPD patients. Studies investigating patients receiving bilevel NIPPV via nasal, oronasal or total face mask interfaces for at least 1 week or more, were described. Eight RCTs were included, from which six trials used NIPPV for up to 3 months (short-term) and two trials also obtained long-term effects (3 months to ≥2 years). Outcome parameters were: arterial blood gases, pulmonary function, respiratory mechanics, respiratory muscle strength, dyspnoea, exercise tolerance, health-related quality of life, neuropsychologic function, sleep quality, hospital admissions and survival. We found that NIPPV in addition to standard care can have beneficial effects on certain outcome measures, however results are conflicting. Therefore, evidence is insufficient to recommend NIPPV routinely in stable but severe COPD patients. Nevertheless, it seems that hypercapnic patients, who receive enough time to adjust to the ventilator and so obtain improved ventilation, could benefit from NIPPV
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