Pilot Trials of STAR Target to Range Glycemic Control

ESICM 2011 programme is available in files INTRODUCTION. Tight glycemic control (TGC) has shown benefits in cardiac surgery ICU patients. STAR (Stochastic TARgeted) is a flexible, model-based TGC protocol accounting for patient variability with a stochastically derived maximum 5% risk of blood glucose (BG) below 90 mg/dL. OBJECTIVES. To assess the safety, efficacy and clinical workload of the STAR TGC controller in pilot trials

The Sudbury Neutrino Observatory

The Sudbury Neutrino Observatory is a second generation water Cherenkov detector designed to determine whether the currently observed solar neutrino deficit is a result of neutrino oscillations. The detector is unique in its use of D2O as a detection medium, permitting it to make a solar model-independent test of the neutrino oscillation hypothesis by comparison of the charged- and neutral-current interaction rates. In this paper the physical properties, construction, and preliminary operation of the Sudbury Neutrino Observatory are described. Data and predicted operating parameters are provided whenever possible.Comment: 58 pages, 12 figures, submitted to Nucl. Inst. Meth. Uses elsart and epsf style files. For additional information about SNO see http://www.sno.phy.queensu.ca . This version has some new reference

Derivative weighted active insulin control algorithms and trials

Close control of blood glucose levels significantly reduces vascular complications in diabetes. Heavy derivative controllers utilising the data density available from emerging biosensors are developed to provide tight, optimal control of elevated blood glucose levels. A two-compartment human model is developed for intravenous infusion from physiologically verified subcutaneous infusion models to enable a first of its kind, proof-of-concept clinical trial. Results show tight control with very similar performance to modelled behaviour and strong correlation between modelled insulin used versus the amounts used in clinical trials to validate the models and methods developed

Modelling Acute Renal Failure using Blood and Breath Biomarkers in Rats

InvitedThis paper compares three methods for estimating renal function, tested in rats. Acute Renal Failure (ARF) was induced via a 60-minute bilateral renal artery clamp in 8 Sprague-Dawley rats and renal function was monitored for 1 week post-surgery. A two-compartment model was developed for estimating renal function via a bolus injection of a radio-labelled inulin tracer, and was compared with the current gold standard plasma creatinine measurement, modified using the Cockcroft-Gault equation for rats. These two methods were compared with Selected Ion Flow Tube-Mass Spectrometry (SIFT-MS) monitoring of breath analytes. Determination of renal function via SIFT-MS is desirable since results are available non-invasively and in real time. Relative decreases in renal function show excellent correlation between methods, and indicate good promise for fast, non-invasive determination of renal function via breath testing

Correlation of Breath Biomarkers with Current Gold Standards for Modelling Acute Renal Failure in Rats

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Modelling acute renal failure using blood and breath biomarkers in rats

Invited. Available online 21 August 2010This paper compares three methods for estimating renal function, as tested in rats. Acute renal failure (ARF) was induced via a 60-min bilateral renal artery clamp in 8 Sprague–Dawley rats and renal function was monitored for 1 week post-surgery. A two-compartment model was developed for estimating glomerular filtration via a bolus injection of a radio-labelled inulin tracer, and was compared with an estimated creatinine clearance method, modified using the Cockcroft–Gault equation for rats. These two methods were compared with selected ion flow tube-mass spectrometry (SIFT-MS) monitoring of breath analytes. Determination of renal function via SIFT-MS is desirable since results are available non-invasively and in real time. Relative decreases in renal function show very good correlation between all 3 methods (R2 = 0.84, 0.91 and 0.72 for breath-inulin, inulin-creatinine, and breath-creatinine correlations, respectively), and indicate good promise for fast, non-invasive determination of renal function via breath testing

Metabolic Model of Autoregulation in the Circle of Willis

The Circle of Willis (CoW) is a ring-like structure of blood vessels found at the base of the brain. Its main function is to distribute oxygen-rich arterial blood to the cerebral mass. In a previous study, a one dimensional model of the CoW was created to simulate a series of possible clinical scenarios such as occlusions in afferent arteries, absent or string-like circulus vessels, or arterial infarctions. The model captured cerebral haemodynamic autoregulation by using a Proportional-Integral-Derivative (PID) controller to modify arterial resistances. Although some good results and correlations were achieved, the model was too simple to capture all the transient dynamics of autoregulation. Hence, a more physiologically accurate model has been created that additionally includes the oxygen dynamics that drive the autoregulatory response. Results very closely match accepted physiological response and limited clinical data. In addition, a se4t of boundary conditions and geometry is presented for which the autoregulated system cannot provide sufficient perfusion, representing a condition with increased risk of stroke and highlighting the importance of modelling the haemodynamics of the CoW. The system model created is computationally simple so it can be used to identify at-risk cerebral arterial geometries and conditions prior to surgery or other clinical procedures

Lumped Parameter and Feedback Control Models of the Auto-Regulatory Response in the Circle of Willis

The Circle of Willis (CoW) is a ring-like structure of blood vessels found beneath the hypothalamus at the base of the brain, which distributes blood to the cerebral mass. Simple models of cerebral blood flow dynamics would create a tool capable of diagnosing potential outcomes of surgical or other therapies. A one-dimensional flow model is developed to capture the auto-regulation dynamics by which cerebral blood perfusion is maintained. Figure 1 shows a CoW schematic composed of circulus, afferent (inflow) and efferent (outflow) arteries. Positive flow around the CoW is clockwise but not restricted in direction, while flow in afferent and efferent vessels is restricted to the directions shown. Flow in efferent vessels is regulated by time varying peripheral resistances modelling the effects of auto-regulation in the smaller blood vessels they supply. While many individuals have complete and symmetrical CoW geometry, it is not uncommon for some elements to be restricted or omitted (van der Zwan and Hillen 1991) with the communicating vessels having a higher occurrence of omission (Alpers and Berry 1963)

Cerebral Haemodynamics and Auto-Regulatory Models of the Circle of Willis

Technical Note. Journal is online only.The Circle of Willis (CoW) is a ring-like structure of blood vessels found beneath the hypothalamus at the base of the brain distributing blood to the cerebral hemispheres. A one-dimensional computational fluid dynamic [1-D CFD] model is developed to capture the auto-regulation dynamics that maintain blood perfusion pressure with a goal of developing diagnostic tools for stroke prediction. The afferent and circulus arteries have constant resistances, and the efferent arteries have variable resistors limited to changes in radius of up to 40% to capture auto-regulatory behaviour. Auto-regulation is modelled by feedback control coupled with peripheral resistance dynamics to create a non-linear system. Solutions are obtained far more quickly than higher dimensional CFD models via a unique non-linear solution method. The overall model enables simulation of different CoW geometries for different patient conditions. The CoW is simulated with a 20mmHg arterial pressure drop in the right internal carotid artery for the balanced configuration and each case where a single circulus vessel is omitted. Results match the 20% drop in flowrate, and 20 second response time from published clinical data and prior research. No single omission leads to failure in reaching the required efferent flowrates, highlighting the overall robustness of this arterial structure. A high stroke risk case, however, fails to achieve the required flowrate in the left posterior communicating artery (LPCA2), representing a potential stroke. All of these results agree well with known clinical results, indicating the potential of this model for pre-determining potential outcomes of surgical or other procedures