Study objective: The three-dimensional shape of the ultrasound beam produces a thicker scan plane than most users assume. Viewed longitudinally, a needle placed lateral to a vessel just outside the central scanning plane can be displayed incorrectly in the ultrasound image as if placed intravascularly. This phenomenon is called the beam width artefact, also known as the elevation or slice thickness artefact. The goal of this study was to demonstrate the potential negative effect of the beam width artefact on the performance of in-plane ultrasound- guided vascular access procedures, and to provide a solution. Design: Randomized, double-blinded study Setting: Department of anaesthesiology and intensive care of a teaching hospital Participants: 31 experienced (anesthesiologists and intensivists) and 36 inexperienced (anesthetic nurses) ultrasound users Interventions: We developed an acoustic lens that narrows the scan plane to reduce the beam width artefact. The lens was tested in a simulated vascular access study. Measurements: The primary endpoint was first pass success. Secondary endpoints were the number of punctures and needle withdrawals, procedure time, needle visibility and operator satisfaction. Main results: First pass success was highly enhanced using the acoustic lens, with a success rate of 92.5% versus 68.7% without the lens (difference 23.8, 95% confidence interval 11.0–35.3, p <0.001). The total number of punctures needed to obtain intravenous access was also reduced using the lens (1.10 versus 1.38, difference 0.27, 95% CI 0.11–0.43, p =0.002). Procedure time, needle withdrawals, needle visibility and satisfaction were similar. Both inexperienced and experienced users benefited from the acoustic lens. Conclusions: The beam width artefact has a significant effect on the performance of ultrasound-guided needle- based procedures. The efficacy of in-plane superficial vascular access procedures can be enhanced by narrowing the imaging plane using an acoustic lens.
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BackgroundOcclusions of intravenous (IV) tubing can prevent vital and time-critical medication or solutions from being delivered into the bloodstream of patients receiving IV therapy. At low flow rates (≤ 1 ml/h) the alarm delay (time to an alert to the user) can be up to 2 h using conventional pressure threshold algorithms. In order to reduce alarm delays we developed and evaluated the performance of two new real-time occlusion detection algorithms and one co-occlusion detector that determines the correlation in trends in pressure changes for multiple pumps.MethodsBench-tested experimental runs were recorded in triplicate at rates of 1, 2, 4, 8, 16, and 32 ml/h. Each run consisted of 10 min of non-occluded infusion followed by a period of occluded infusion of 10 min or until a conventional occlusion alarm at 400 mmHg occurred. The first algorithm based on binary logistic regression attempts to detect occlusions based on the pump’s administration rate Q(t) and pressure sensor readings P(t). The second algorithm continuously monitored whether the actual variation in the pressure exceeded a threshold of 2 standard deviations (SD) above the baseline pressure. When a pump detected an occlusion using the SD algorithm, a third algorithm correlated the pressures of multiple pumps to detect the presence of a shared occlusion. The algorithms were evaluated using 6 bench-tested baseline single-pump occlusion scenarios, 9 single-pump validation scenarios and 7 multi-pump co-occlusion scenarios (i.e. with flow rates of 1 + 1, 1 + 2, 1 + 4, 1 + 8, 1 + 16, and 1 + 32 ml/h respectively). Alarm delay was the primary performance measure.ResultsIn the baseline single-pump occlusion scenarios, the overall mean ± SD alarm delay of the regression and SD algorithms were 1.8 ± 0.8 min and 0.4 ± 0.2 min, respectively. Compared to the delay of the conventional alarm this corresponds to a mean time reduction of 76% (P = 0.003) and 95% (P = 0.001), respectively. In the validation scenarios the overall mean ± SD alarm delay of the regression and SD algorithms were respectively 1.8 ± 1.6 min and 0.3 ± 0.2 min, corresponding to a mean time reduction of 77% and 95%. In the multi-pump scenarios a correlation > 0.8 between multiple pump pressures after initial occlusion detection by the SD algorithm had a mean ± SD alarm delay of 0.4 ± 0.2 min. In 2 out of the 9 validation scenarios an occlusion was not detected by the regression algorithm before a conventional occlusion alarm occurred. Otherwise no occlusions were missed.ConclusionsIn single pumps, both the regression and SD algorithm considerably reduced alarm delay compared to conventional pressure limit-based detection. The SD algorithm appeared to be more robust than the regression algorithm. For multiple pumps the correlation algorithm reliably detected co-occlusions. The latter may be used to localize the segment of tubing in which the occlusion occurs.
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This paper puts forward a conceptual proposition that ties the discourses on ‘urban memory’ (Stillman and Johanson, 2009; Ringas, Christopoulou, Stefanidakis., 2011; Loughran, Fine & Hunter, 2015), sensory ethnography (Pink 2017 ), and counter-mapping (Crampton and Krygier 2018; ) with digital methods (Rogers, Sánchez-Querubín, and Kil, 2015). As an ‘interventionist’ approach, we understand co-producing counter (dynamic) maps with local stakeholders (actors), coupled with sensory and sentient data as a way of capturing the memory of urban peripheral landscapes (through intervention and participation) and thus creating archival knowledge.Urban memory is often understood as a form of collective memory that isconstituted by individual experiences within the place itself and through its historyand social environment (Ringas et al., 2011). With rapid changes in digitaltechnologies, digital and material have become “inseparate and entangled inenvironments people move and navigate their lives through'' (Pink and Fors, 2017).Memories are “evoked with material engagement with devices” which “opens up afield of sensory and affective engagement” research (ibid). While Pink and Forspropose to follow such engagement in a mundane and everyday setting, seen as anon-representational, phenomenological approach, we put forward a mixedmethods approach that connects sensory and sentient data (as agents) with the largerenvironmental context.Urban areas are often conceptualized as sites of ‘creative destruction’, in between stability and change, space (that can be developed) and place (that is lived in), often subjected to planning, regulation, and economic forces (Batty, 2007). This is especially true for urban areas that are located outside of the ‘center’ or in the cities’ periphery. These areas have experienced an endless cycle of deconstruction and reconstruction often witnessed and captured by local inhabitants, creatives, and activists. Currently, many of the peripheral areas are emancipating, bringing forward and openly communicating their complexities, values, and engaging various stakeholders in their regeneration efforts (which happens in a broader context of many European cities repositioning themselves in more polycentric and polyphonic ways, (Scott, 2015).To be able to capture the memory of ever-changing, ‘built a new’ urban places, we put forward counter (dynamic) mapping using digital methods as complemented with sensory and sentient data generated through interactions with digital technologies. Building on Crampton’s notion of maps (Crampton and Krygier, 2018), cartography is understood as existence (becoming) rather than essence (fixed ontology). Maps are therefore taken not as ‘objects’, but as performative practices. Digital methods, on the other hand, enable us to understand dynamic place-making, through ‘tracing’ the stakeholders (actors) and their relations overtime to capture the ways the urban environment gets performed.To clarify with an example, in Spinoza Imaginaries Lab & Cafe situated inAmsterdam Southeast we have been capturing the ever changing urbanenvironment in partnership with local stakeholders (actors), mapping their evolvingrelationships (and grouping) using the IssueCrawler and sentient data co-gatheredby researchers and students, with the clear understanding that to be able to capturea place, it is important to map the vernacular knowledge of that place (imaginaries,including art, movies, unrealized plans and initiatives, etc.). We propose this mixedmethods approach as an epistemological practice geared towards archiving thedynamic state of urban peripheral landscapes.
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