PubMed Health⌕ Search

SEARCH · PubMed Health

Results for “optimal control”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 253 records · Page 14Linked to original sources
PubMed1999

A rational approach to the control of sedation in intensive care unit patients based on closed-loop control.

Optimal control of long-term sedation during therapy in the intensive care unit is difficult to achieve in a number of patients when based on commonly used clinical sedation scores alone. We therefore used the median frequency of the EEG power spectrum as a quantitative measure for closed-loop administration of propofol in 21 artificially ventilated patients (nine trauma, 12 non-trauma). The EEG setpoint was correlated with a clinical sedation score and defined such, that mechanical ventilation was tolerated. The sedative therapy was given for 31 +/- 30 h. Non-trauma patients required sedation with an EEG median frequency between 2 and 3 Hz (propofol consumption: 1.4 +/- 0.8 mg kg-1 h-1) and sedation seemed to follow some circadian patterns, whereas trauma patients needed significantly deeper sedation (EEG median frequency: 1-2 Hz; propofol consumption: 2.6 +/- 0.8 mg kg-1 h-1). We conclude that the EEG closed-loop system could safely and reliably administer propofol to maintain a predetermined level of sedation for patients in intensive care unit over a protracted time.

APACHE↗
PubMed2004

Exogenous and endogenous postprandial lipid abnormalities in type 2 diabetic patients with optimal blood glucose control and optimal fasting triglyceride levels.

The aim of this study was to evaluate exogenous and endogenous lipoprotein responses to a standard fat-rich meal in type 2 diabetic patients with optimal fasting triglyceridemia and optimal blood glucose control. Seven type 2 diabetic patients and five nondiabetic controls (age, 49 +/- 7 and 48 +/- 4 yr; body mass index, 28.3 +/- 3.6 and 25.1 +/- 3.6 kg/m(2); mean +/- SD) were given, after at least 12 h of fasting, a standard fat-rich meal. Before and over the 6 h after the meal, serial blood samples were taken for determination of glucose, insulin, lipids, lipoproteins, apolipoprotein B-48 (apo B-48), apo B-100, free fatty acids, and lipoprotein lipase activity. The main abnormality in the postprandial lipid response of diabetic patients involved large very low density lipoproteins. In these particles, apo B-48, apo B-100, cholesterol, and triglyceride incremental areas were, in fact, significantly higher in diabetics compared with controls [7.08 +/- 2.65 vs. 1.17 +/- 0.88 mg/liter.h, 65.5 +/- 11.5 vs. 12.4 +/- 1.77 mg/liter.h, 29.7 +/- 3.9 vs. 13.1 +/- 3.1 mg/dl.h (0.77 +/- 0.10 vs. 0.34 +/- 0.08 mmol/liter.h), 170 +/- 31 vs. 94 +/- 22 mg/dl.h (1.93 +/- 0.35 vs. 1.06 +/- 0.25 mmol/liter.h)] (all P < 0.05; mean +/- SEM). Postprandial preheparin lipoprotein lipase plasma activity was, if anything, higher in diabetic patients. In conclusion, even with fasting normotriglyceridemia and optimal blood glucose control, type 2 diabetic patients are characterized, in the postprandial period, by a significant increase in large very low density lipoproteins of both endogenous and exogenous origins.

Blood Glucose↗
PubMed1996

Exponentially adjusted moving mean procedure for quality control. An optimized patient sample control procedure.

The idea of using patient samples as the basis for control procedures elicits a continuing fascination among laboratorians, particularly in the current environment of cost restriction. Average of normals (AON) procedures, although little used, have been carefully investigated at the theoretical level. The performance characteristics of Bull's algorithm have not been thoroughly delineated, however, despite its widespread use. The authors have generalized Bull's algorithm to use variably sized batches of patient samples and a range of exponential factors. For any given batch size, there is an optimal exponential factor to maximize the overall power of error detection. The optimized exponentially adjusted moving mean (EAMM) procedure, a variant of AON and Bull's algorithm, outperforms both parent procedures. As with any AON procedure, EAMM is most useful when the ratio of population variability to analytical variability (standard deviation ratio, SDR) is low.

Algorithms↗
PubMed1993

Control strategies for arterial blood pressure regulation.

This paper reviews the theoretical development of automatic control strategies for arterial blood pressure regulation. The literature is classified by control strategy. Proportional-integral-derivative controllers, optimal controllers, adaptive controllers, and rule-based controllers are the most commonly encountered strategies in the literature. A brief description of each control scheme is given, followed by examples of each from the literature. Validation methods for the control performance vary from computer simulations to clinical tests on human patients. A number of reports of clinical success support the feasibility of advanced control systems in this problem. Issues on control systems in the clinical environment are also discussed.

Animals↗
PubMed1996

Space stress and genome shock in developing plant cells.

In the present paper I review symptoms of stress at the level of the nucleus in cells of plants grown in space under nonoptimized conditions. It remains to be disclosed to what extent gravity "unloading" in the space environment directly contributes to the low mitotic index and the chromosomal anomalies and damage that is frequently, but not invariably, demonstrable in space-grown plants. Evaluation of the available facts indicates that indirect effects play a major role and that there is a significant biological component to the susceptibility to stress damage equation as well. Much remains to be learned on how to provide strictly controlled, optimal environments for plant growth in space. Only after optimized controls become possible will one be able to attribute any observed space effects to lowered gravity or to other significant but more indirect effects of the space environment.

Cell Cycle↗
PubMed2005

Optimal modal fourier-transform wavefront control.

Optimal modal Fourier-transform wavefront control combines the speed of Fourier-transform reconstruction (FTR) with real-time optimization of modal gains to form a fast, adaptive wavefront control scheme. Our modal basis is the real Fourier basis, which allows direct control of specific regions of the point-spread function. We formulate FTR as modal control and show how to measure custom filters. Because the Fourier basis is a tight frame, we can use it on a circular aperture for modal control even though it is not an orthonormal basis. The modal coefficients are available during reconstruction, greatly reducing computational overhead for gain optimization. Simulation results show significant improvements in performance in low-signal-to-noise-ratio situations compared with nonadaptive control. This scheme is computationally efficient enough to be implemented with off-the-shelf technology for a 2.5 kHz, 64 x 64 adaptive optics system.

Journal Article↗
PubMed1996

Blood pressure control of drug treated hypertension in 18 general practices.

This study examined the blood pressure (BP) control and number of drugs prescribed for a sample of hypertensive patients from 18 practices in Northeast England. Out of a total of 35,379 registered patients aged 40-69 years, 2995 (8.5%) were on treatment for hypertension. Data was abstracted from the practice records of a random sample of 691 patients. Using British Hypertension Society standards, BP control was optimal for systolic pressure (less than 160 mm Hg) in 469 (68%), and for diastolic pressure (less than 90 mm Hg) in 345 (50%), but only 269 (39%) had optimally controlled systolic and diastolic pressures. Sixty-one per cent were taking one drug and 39% two or more; 82% of patients aged 40-49 years but only 61% of those aged 60-69 years had optimally controlled systolic pressures. Forty-three per cent of the 40 to 49-year-old group and 56% of the 60 to 69-year-old group had optimally controlled diastolic pressures. A strong inverse relationship was found between age and systolic BP control but there was no association between age and diastolic pressure or the number of drugs being prescribed. Sub-optimal BP control is a major problem and remedial strategies should stress the greater gain from treating older patients.

Adult↗
PubMedDate not supplied

Adaptive, model-based control by the Open-Loop-Feedback-Optimal (OLFO) controller for the effective fed-batch cultivation of hybridoma cells.

Although fed-batch suspension culture of animal cells continues to be of industrial importance for the large scale production of pharmaceutical products, existing control concepts are still insufficient. Changes in cell metabolism during cultivation and between similar cultivations, the complexity of the cell metabolism, and the lack of on-line state variables restrict the transfer of available control strategies established in bioprocess engineering. A process control strategy designed to achieve optimized process control must account for all these difficulties and fit sophisticated requirements toward adaptability and flexibility. The combination of a fed-batch process and an Open-Loop-Feedback-Optimal (OLFO) control provides a new approach for cell culture process control that couples an efficient cultivation concept to a capable process control strategy. The application of an adaptive, model-based OLFO controller to a hybridoma cultivation and experimental results are presented.

Algorithms↗