Multiple studies have defined criteria for the selection of thyroid nodules for biopsy. No set of criteria is sufficiently sensitive and specific. The aim of this study is to develop a method for ...assessing consistency of practice in an ultrasound group and to determine whether a 5-point malignancy rating scale can be used to select patients for biopsy.
One hundred one nodules (50 benign and 51 malignant) were selected from a thyroid biopsy database. Seven radiologists were educated on evidence-based criteria used to select nodules for biopsy. Using this information, readers graded the likelihood of malignancy using a 5-point malignancy rating scale, where 1 equals the lowest probability of malignancy and 5 equals the highest probability of malignancy, on the basis of overall impression of sonographic findings. Interobserver agreement on biopsy recommendation, reader sensitivity, specificity, and accuracy were determined.
The sensitivity and specificity of biopsy recommendation were 96.1% and 52%, respectively. The misclassification rate was 25.7%, and accuracy was 74.3%. Interobserver agreement on biopsy recommendation was fair to substantial (κ, 0.38-0.69). The proportion of agreement was excellent for malignant nodules (0.88-1.0). The risk of malignancy increased with increasing malignancy rating: 4.3% of nodules with a malignancy rating of 1 were malignant versus 93.4% of those assigned a rating of 5.
Our study illustrates a method to evaluate the standard of practice for thyroid nodule assessment among radiologists within an ultrasound group. Application of a 5-point malignancy rating scale to select nodules for biopsy is feasible and shows good diagnostic accuracy.
The application of positive end expiratory pressure (PEEP) in mechanically ventilated (MV) patients with acute respiratory distress syndrome (ARDS) decreases cardiac output (CO). Accurate measurement ...of CO is highly invasive and is not ideal for all MV critically ill patients. However, the link between the PEEP used in MV, and CO provides an opportunity to assess CO via MV therapy and other existing measurements, creating a CO measure without further invasiveness.This paper examines combining models of diffusion resistance and lung mechanics, to help predict CO changes due to PEEP. The CO estimator uses an initial measurement of pulmonary shunt, and estimations of shunt changes due to PEEP to predict CO at different levels of PEEP. Inputs to the cardiac model are the PV loops from the ventilator, as well as the oxygen saturation values using known respiratory inspired oxygen content. The outputs are estimates of pulmonary shunt and CO changes due to changes in applied PEEP. Data from two published studies are used to assess and initially validate this model.The model shows the effect on oxygenation due to decreased CO and decreased shunt, resulting from increased PEEP. It concludes that there is a trade off on oxygenation parameters. More clinically importantly, the model also examines how the rate of CO drop with increased PEEP can be used as a method to determine optimal PEEP, which may be used to optimise MV therapy with respect to the gas exchange achieved, as well as accounting for the impact on the cardiovascular system and its management.
To compare ultrasound (US) to angiography combined with computed tomography during arterial portography (CTAP) in the preoperative evaluation of the portal vein.
Sixty-three consecutive patients ...being considered for hepatic resection underwent color and spectral Doppler US and angiography with CTAP before surgery. The main, right, and left portal veins were evaluated separately. A total of 187 veins were assessed for encasement, occlusion, or thrombosis.
At surgery, 41 portal veins were abnormal. US allowed detection of 38 of 41 (93%) involved portal veins with 93% sensitivity, 99% specificity, 97% positive predictive value, and 98% negative predictive value. Angiography with CTAP allowed diagnosis of 37 of 41 (90%) involved portal veins with 90% sensitivity, 99% specificity, 95% positive predictive value, and 97% negative predictive value.
US is comparable to angiography combined with CTAP in evaluation of the portal vein.
Abstract The effective delivery of sedation in critical care relies primarily on an accurate and consistent measure of a patient's agitation level. However, current methods for assessing agitation ...are subjective and prone to error, often leading to over sedation or cycles between agitation and oversedation. This paper builds on previous work developing agitation sensors based on heart rate and blood pressure variability, and overall whole body motion. In this research, the focus is on real-time measurement of high-resolution facial changes that are observed to occur in agitation. An algorithm is developed that measures the degree of facial grimacing from a single digital camera. The method is demonstrated on simulated patient facial motion to prove the concept. A consistent measure is obtained that is robust to significant random head movement and compares well against visual observation of different levels of grimacing. The method provides a basis for clinical validation.
A minimal cardiac model has been developed which accurately captures the essential dynamics of the cardiovascular system (CVS). However, identifying patient specific parameters with the limited ...measurements often available, hinders the clinical application of the model for diagnosis and therapy selection. This paper presents an integral-based parameter identification method for fast, accurate identification of patient specific parameters using limited measured data. The integral method turns a previously non-linear and non-convex optimization problem into a linear and convex identification problem.
The model includes ventricular interaction and physiological valve dynamics. A healthy human state and four disease states, valvular stenosis, pulmonary embolism, cardiogenic shock and septic shock are used to test the method. Parameters for the healthy and disease states are accurately identified using only discretized flows into and out of the two cardiac chambers, the minimum and maximum volumes of the left and right ventricles, and the pressure waveforms through the aorta and pulmonary artery. These input values can be readily obtained non-invasively using echo-cardiography and ultra-sound, or invasively via catheters that are often used in Intensive Care.
The method enables rapid identification of model parameters to match a particular patient condition in clinical real time (3–5 min) to within a mean value of 4–10% in the presence of 5–15% uniformly distributed measurement noise. The specific changes made to simulate each disease state are correctly identified in each case to within 10% without false identification of any other patient specific parameters. Clinically, the resulting patient specific model can then be used to assist medical staff in understanding, diagnosis and treatment selection.
Abstract A cardiovascular system (CVS) model has previously been validated in simulated cardiac and circulatory disease states. It has also been shown to accurately capture all main hemodynamic ...trends in a porcine model of pulmonary embolism. In this research, a slightly extended CVS model and parameter identification process are presented and validated in a porcine experiment of positive end-expiratory pressure (PEEP) titrations at different volemic levels. The model is extended to more physiologically represent the separation of venous and arterial circulation. Errors for the identified model are within 5% when re-simulated and compared to clinical data. All identified parameter trends match clinically expected changes. This work represents another clinical validation of the underlying fundamental CVS model, and the methods and approach of using them for cardiovascular diagnosis in critical care.
Dynamic insulin sensitivity (
SI) tests often utilise model-based parameter estimation. This research analyses the impact of expanding the typically used two-compartment model of insulin and ...C-peptide kinetics to incorporate a hepatic third compartment. The proposed model requires only four C-peptide assays to simulate endogenous insulin production (
uen), greatly reducing the cost and clinical burden.
Sixteen subjects participated in 46 dynamic insulin sensitivity tests (DIST). Population kinetic parameters are identified for the new compartment. Results are assessed by model error versus measured data and repeatability of the identified SI.
The median C-peptide error was 0% (IQR: −7.3, 6.7)%. Median insulin error was 7% (IQR: −28.7, 6.3)%. Strong correlation (
r
=
0.92) existed between the SI values of the new model and those from the original two-compartment model. Repeatability in SI was similar between models (new model inter/intra-dose variability 3.6/12.3% original model −8.5/11.3%).
When frequent C-peptide samples may be available, the added hepatic compartment does not offer significant diagnostic, repeatability improvement over the two-compartment model. However, a novel and successful three-compartment modelling strategy was developed which provided accurate estimation of endogenous insulin production and the subsequent SI identification from sparse C-peptide data.
Acceptance and Commitment Therapy (ACT) is a form of Cognitive Behavioral Therapy that includes a specific therapeutic process, “psychological flexibility,” and focuses on behavior change rather than ...symptom reduction. One relatively well-developed research area includes ACT applied to chronic pain. The current systematic review examines outcome domains included as primary, secondary and process variables in controlled trials of ACT-based pain treatment studies, and also summarizes evidence for efficacy. The review of outcome domains is to establish whether these are in-line with recommendations, consistent with the theory underlying ACT, and optimal for further development. A systematic search identified 1034 articles and ten studies were selected as eligible for review. Overall, 15 outcome domains were assessed using 39 different measurement tools across the ten RCTs. The outcome domains assessed in the reviewed trials were, to an extent, in-line with recognized guidelines. Six of the ten studies identified primary and secondary outcomes; one included just one outcome and three did not categorize outcomes. All ten trials included a measure of some aspect of psychological flexibility; however these were not always formally identified as process variables. Pain and emotional functioning were the most frequently measured outcome domains. A review of outcome results suggests that ACT is efficacious particularly for enhancing general, mostly physical functioning, and for decreasing distress, in comparison to inactive treatment comparisons. It is recommended that future RCTs (a) formally define outcomes as primary, secondary and process variables, (b) consider including measures of physical or social functioning, rather than pain and emotional functioning, as primary outcomes, (c) address existing risks of bias, such as reporting bias, and (d) include more components of psychological flexibility, such as cognitive defusion and self-related variables.
•There are now at least ten RCTs (using an inclusive definition of this term) that address ACT for chronic pain.•These include assessment of 15 separate outcome domains with 39 different instruments.•Articles on ACT for chronic pain do not always classify their measures as primary, secondary, or process, but should do.•ACT appears superior to inactive treatments for chronic pain.
Abstract A majority of patients admitted to the Intensive Care Unit (ICU) require some form of respiratory support. In the case of Acute Respiratory Distress Syndrome (ARDS), the patient often ...requires full intervention from a mechanical ventilator. ARDS is also associated with mortality rate as high as 70%. Despite many recent studies on ventilator treatment of the disease, there are no well established methods to determine the optimal Positive End-Expiratory Pressure (PEEP) or other critical ventilator settings for individual patients. A model of fundamental lung mechanics is developed based on capturing the recruitment status of lung units. The main objective of this research is to develop a minimal model that is clinically effective in determining PEEP. The model was identified for a variety of different ventilator settings using clinical data. The fitting error was between 0.1% and 4% over the inflation limb and between 0.3% and 13% over the deflation limb at different PEEP settings. The model produces good correlation with clinical data, and is clinically applicable due to the minimal number of patient specific parameters to identify. The ability to use this identified patient specific model to optimize ventilator management is demonstrated by its ability to predict the patient specific response of PEEP changes before clinically applying them. Predictions of recruited lung volume change with change in PEEP have a median absolute error of 1.87% (IQR: 0.93–4.80%; 90% CI: 0.16–11.98%) for inflation and a median of 5.76% (IQR: 2.71–10.50%; 90% CI: 0.43–17.04%) for deflation, across all data sets and PEEP values ( N = 34 predictions). This minimal model thus provides a clinically useful and relatively simple platform for continuous patient specific monitoring of lung unit recruitment for a patient.
Abstract
The present paper investigates a severe gear backlash problem encountered in a stiff stay machine that is capable of producing a 26-line fence up to 2.6 m in height at a speed of 80 ...stays/min. Related problems in the literature typically concentrate on the effect of gear backlash on the ability to control a shaft. However, in this case, very good control of the reference speed of the shaft was maintained in spite of the gear backlash. The problem was that the commanded torques were excessively large and threatened to damage the gearbox. This problem motivated a complete analysis of the system's dynamics including the development of a model to better understand the response and allow the identification of external loads on the system. It was found that the method of sensing the shaft position (resolvers) was a major factor as well as the upgrading of the motor, which was over-responding to disturbances in the shaft. The model was validated using several torque limiting experiments and gave accurate prediction of the machine's major dynamics. The simulation tool developed provides the basis to predict the effect of different loads, wire types, and/or motors on the machine for future designs, minimizing the amount of experimentation on the machine.
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