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Stephan Hess,1 Martin Dubach,2 Mirko Meboldt,1 Lukas Foggensteiner3 1Swiss Federal Institute of Technology in Zurich (ETH Zurich), Zurich, Switzerland; 2Peripal AG; 3University Hospitals Birmingham NHS Foundation Trust, Birmingham, United KingdomCorrespondence: Stephan HessSwiss Federal Institute of Technology in Zurich (ETH Zurich), Leonhardstrasse 21, Zurich CH 8092, SwitzerlandTel +41 44 632 48 62Email stehess@ethz.chIntroduction: It is estimated that there are currently over 3 million patients receiving dialysis treatment worldwide. With effective pre-dialysis counselling, a majority of patients choose the home-based therapy peritoneal dialysis (PD) but only approximately 11% of prevalent dialysis patients use this modality. Connection-assist devices can overcome the challenges posed by decreased manual dexterity and/or visual acuity, and can allow more patients to be treated with home-based therapies. As part of the CE marking authorization, a connection device has been evaluated for safety and ease of use in a usability study.Methods: Fifteen patients and nine carers volunteered in this study, ranging from 23 to 86 years in age and from 0.3 to 24 years in experience in the PD therapy. The operating cycle consisted of eight tasks, each having several handling steps. The data analysis focused on the task effectiveness and the subjects’ subjective feedback from the NASA task load index (N-TLX) questionnaire and semi-structured interviews.Results: Of 1248 handling steps performed in total, 38 use errors were observed and discussed with the subjects. This equates to 97% of all handling steps being performed safely and easily. In all six dimensions of the N-TLX, more than 50 percent of subjects rated the task load 50 points or less on the scale. Regarding the handling of the device, 13 of 15 of the patients and 8 of 9 of the carers gave positive feedback.Discussion: Safety and ease of use was demonstrated by evaluating task effectiveness (97% SU), interviews and N-TLX. Additionally the study provided valuable individual user feedback, which will inform the final design of the system for PD. The majority of patients and carers gave positive feedback regarding use and handling of this connection device. Innovative connection devices in general promise to reduce the barriers to using this home-based dialysis treatment.Keywords: patient safety, usability study, ease of use, connection-assist device, peritoneal dialysis, NASA Task Load Index

The user's gaze can provide important information for human–machine interaction, but the analysis of manual gaze data is extremely time-consuming, inhibiting wide adoption in usability studies. Existing methods for automated areas of interest (AOI) analysis cannot be applied to tangible products with a screen-based user interface (UI), which have become ubiquitous in everyday life. The objective of this paper is to present and evaluate a method to automatically map the user's gaze to dynamic AOIs on tangible screen-based UIs based on computer vision and deep learning. This paper presents an algorithm for automated Dynamic AOI Mapping (aDAM), which allows the automated mapping of gaze data recorded with mobile eye tracking to the predefined AOIs on tangible screen-based UIs. The evaluation of the algorithm is performed using two medical devices, which represent two extreme examples of tangible screen-based UIs. The different elements of aDAM are examined for accuracy and robustness, as well as the time saved compared to manual mapping. The break-even point for an analyst's effort for aDAM compared to manual analysis is found to be 8.9 min gaze data time. The accuracy and robustness of both the automated gaze mapping and the screen matching indicate that aDAM can be applied to a wide range of products. aDAM allows, for the first time, automated AOI analysis of tangible screen-based UIs with AOIs that dynamically change over time. The algorithm requires some additional initial input for the setup and training, but analyzed gaze data duration and effort is only determined by computation time and does not require any additional manual work thereafter. The efficiency of the approach has the potential for a broader adoption of mobile eye tracking in usability testing for the development of new products and may contribute to a more data-driven usability engineering process in the future. [ABSTRACT FROM AUTHOR]

Syringe infusion pumps are used for the administration of short-acting drugs in anaesthesia and critical care medicine, but are prone to flow irregularities at low flow rates. A flow-controlled syringe infusion pump using an integrated flow sensor for feedback control represents a new approach to overcoming these limitations. This study compares the performance of a prototype flow-controlled syringe pump both at start-up, and during vertical displacement manoeuvres, with that of a standard infusion syringe pump. The novel pump almost completely eliminated delays at start-up and flow irregularities during hydrostatic pressure changes. Related fluctuations in plasma drug concentration were minimised and the known disadvantages of standard syringe infusion pumps currently used in clinical practice were reduced. Besides providing fast start-up to steady-state flow and precise continuous drug delivery at low flow rates during hydrostatic pressure changes, the new pump offers the potential for the development of target-controlled infusion algorithms for short-acting cardiovascular and other drugs. [ABSTRACT FROM AUTHOR]

Patients with ventricular assist devices still suffer from high rates of adverse events. Since many of these complications are linked to the flow field within the pump, optimization of the device geometry is essential. To investigate design aspects that influence the flow field, we developed a centrifugal blood pump using industrial guidelines. We then systematically varied selected design parameters and investigated their effects on hemodynamics and hydraulic performance using computational fluid dynamics. We analysed the flow fields based on Eulerian and Lagrangian features, shear stress histograms and six indicators of hemocompatibility. Within the investigated range of clearance gaps (50-500 µm), number of impeller blades (4-7), and semi-open versus closed shroud design, we found association of potentially damaging shear stress conditions with larger gap size and more blades. The extent of stagnation and recirculation zones was reduced with lower numbers of blades and a semi-open impeller, but it was increased with smaller clearance. The Lagrangian hemolysis index, a metric commonly applied to estimate blood damage, showed a negative correlation with hydraulic efficiency and no correlation with the Eulerian threshold-based metric. [ABSTRACT FROM AUTHOR]

Introduction: In radiotherapy, tumors may move due to the patient’s respiration, which decreases treatment accuracy. Some motion mitigation methods require measuring the tumor position during treatment. Current available sensors often suffer from time delays, which degrade the motion mitigation performance. However, the tumor motion is often periodic and continuous, which allows predicting the motion ahead. Method and Materials: A couch tracking system was simulated in MATLAB and five prediction filters selected from literature were implemented and tested on 51 respiration signals (median length: 103 s). The five filters were the linear filter (LF), the local regression (LOESS), the neural network (NN), the support vector regression (SVR), and the wavelet least mean squares (wLMS). The time delay to compensate was 320 ms. The normalized root mean square error (nRMSE) was calculated for all prediction filters and respiration signals. The correlation coefficients between the nRMSE of the prediction filters were computed. Results: The prediction filters were grouped into a low and a high nRMSE group. The low nRMSE group consisted of the LF, the NN, and the wLMS with a median nRMSE of 0.14, 0.15, and 0.14, respectively. The high nRMSE group consisted of the LOESS and the SVR with both a median nRMSE of 0.34. The correlations between the low nRMSE filters were above 0.87 and between the high nRMSE filters it was 0.64. Conclusion: The low nRMSE prediction filters not only have similar median nRMSEs but also similar nRMSEs for the same respiration signals as the high correlation shows. Therefore, good prediction filters perform similarly for identical respiration patterns, which might indicate a minimally achievable nRMSE for a given respiration pattern.

Ventricular end-diastolic volume (EDV) is an important parameter for monitoring patients with heart pumps, and for informing an algorithm to adapt the pump speed in a smart way. Continuous information on the EDV is unavailable to date. We hypothesize that the depolarization amplitude of the non-contact intra-cardiac electromyogram (iEMG) is physically related to the EDV. Thus, it could serve as a useful measure for predicting EDV in these patients. The study was performed in six pigs while undergoing a series of significant changes in hemodynamic states. Four conventional pacemaker electrodes measured the far-field iEMG inside the left ventricular blood pool, using a novel unipolar amplifier. Simultaneously, measurements of preload and hematocrit were recorded. The proposed EDV predictor was tested for statistical significance using a mixed effect model and associated confidence intervals. A statistically significant (p<0.005) negative correlation was confirmed between the amplitude of the iEMG and the EDV measured by electric impedance at a slope of -0.063 (-0.066, -0.060) mV/mL. The influence of the hematocrit was not found significant. All measurements of the four distinct electrodes yielded comparable results. The amplitude of the iEMG proved a significant, independent predictor of the EDV. Electrodes are simple to integrate into the cannula of a heart pump. Because of their simplicity, electrodes shall be incorporated in the inflow cannula of heart pumps. Given the manifold determinants of the depolarization amplitude, a combination with a mechanical signal, such as pump flow, is likely to further increase robustness. In this way, the iEMG has the potential to inform the clinician about the state of the patient in real-time and to control the pump in a smart way. [ABSTRACT FROM AUTHOR]