131 research outputs found
Aortic dP/dtmax accurately reflects left ventricular contractility when effective preload independence is achieved
peer reviewe
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
Model-based cardiovascular monitoring of acute pulmonary embolism in porcine trials
Introduction:
Diagnosis and treatment of cardiac and circulatory dysfunction can be error-prone and relies heavily on clinical
intuition and experience. Model-based approaches utilising measurements available in the Intensive care unit
(ICU) can provide a clearer physiological picture of a patient’s cardiovascular status to assist medical staff with
diagnosis and therapy decisions. This research tests a subject-specific cardiovascular system (CVS) modelling
technique on measurements from a porcine model of acute pulmonary embolism (APE).
Methods:
Measurements were recorded in 5 pig trials, where autologous blood clots were inserted every two hours into
the jugular vein to simulate pulmonary emboli. Of these measurements only a minimal set of clinically available or
inferable data were used in the identification process (aortic and pulmonary artery pressure, stroke volume, heart
rate, global end diastolic volume, and mitral and tricuspid valve closure times).
The CVS model was fitted to 46 sets of data taken at 30 minute intervals (t=0, 30, 60, …, 270) during the induction
of APE to identify physiological model parameters and their change over time in APE. Model parameters and
outputs were compared to experimentally derived metrics and measurements not used in the identification
method to validate the accuracy of the model and assess its diagnostic capability.
Results:
Modelled mean ventricular volumes and maximum ventricular pressures matched measured values with median
absolute errors of 4.3% and 4.4%, which are less than experimental measurement noise (~10%). An increase in
pulmonary vascular resistance, the main hemodynamic consequence of APE, was identified in all the pigs and
related well to experimental values (R=0.68). Detrimental changes in reflex responses, such as decreased right
ventricular contractility, were noticed in two pigs that died during the trial, diagnosing the loss of autonomous
control. Increases in the ratio of the modelled right to left ventricular end diastolic volumes, signifying the
leftward shift of the intra-ventricular septum seen in APE, compared well to the clinically measured index
(R=0.88).
Conclusions:
Subject-specific CVS models can accurately and continuously diagnose and track acute disease dependent
cardiovascular changes resulting from APE using readily available measurements. Human trials are underway to
clinically validate these animal trial results
Pulmonary embolism diagnostics from the driver function
Ventricular driver functions are not readily measured in the ICU, but can clearly indicate the development of pulmonary embolism (PE) otherwise difficult to diagnose. Recent work has developed accurate methods of
measuring these driver functions from readily available ICU measurements. This research tests those methods by assessing the ability of these driver functions to diagnose the evolution of PE
Enhanced insulin sensitivity variability in the first 3 days of ICU stay: implications for tight glycemic control
Effective tight glycemic control (TGC) can improve outcomes, particularly in cardiovascular surgery, but is
difficult to achieve. Variability in insulin sensitivity/resistance resulting from the level and evolution of stress
response, particularly early in a patient’s stay, can lead to hyperglycemia and variability, which are associated
with mortality. This study quantifies the daily evolution of the variability of insulin sensitivity for cardiovascular
surgical and all other ICU patients
Amplitude equations for Rayleigh-Benard convective rolls far from threshold
An extension of the amplitude method is proposed. An iterative algorithm is developed to build an amplitude equation model that is shown to provide precise quantitative results even far from the linear instability threshold. The method is applied to the study of stationary Rayleigh-Benard thermoconvective rolls in the nonlinear regime. In particular, the generation of second and third spatial harmonics is analyzed. Comparison with experimental results and direct numerical calculations is also made and a very good agreement is found.Peer reviewe
Effect of various Neurally adjusted ventilatory assist (NAVA) gains on the relationship between diaphragmatic activity (Eadi max) and tidal volume (Vt)
ESICM 2011 programme is available in notes
http://www.springerlink.com/content/m0xth64u3885w270/</a
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