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PubMed2007

Physical activity and motor decline in older persons.

We tested the hypothesis that physical activity modifies the course of age-related motor decline. More than 850 older participants of the Rush Memory and Aging Project underwent baseline assessment of physical activity and annual motor testing for up to 8 years. Nine strength measures and nine motor performance measures were summarized into composite measures of motor function. In generalized estimating equation models, global motor function declined during follow-up (estimate, -0.072; SE, 0.008; P < 0.001). Each additional hour of physical activity at baseline was associated with about a 5% decrease in the rate of global motor function decline (estimate, 0.004; SE, 0.001; P = 0.007). Secondary analyses suggested that the association of physical activity with motor decline was mostly due to the effect of physical activity on the rate of motor performance decline. Thus, higher levels of physical activity are associated with a slower rate of motor decline in older persons.

Activities of Daily Living↗

PubMed1986

[Combined use of thrombolysis and PTCA in myocardial infarct. Effect on global and regional ventricular function].

The study was performed to evaluate the combined effect of thrombolysis therapy and percutaneous coronary transluminal angioplasty (PTCA) on global and regional left ventricular function. In 127 patients with acute transmural myocardial infarction combined intravenous (250 000 U) and intracoronary (50 000 U) streptokinase therapy was started. When the infarct related vessel was occluded mechanical recanalization was performed with recanalization by Gruentzig balloon catheters. Patients were randomized in two groups, group I, n = 64, thrombolysis without PTCA; group II, n = 63, thrombolysis with PTCA. Both groups demonstrated no difference in relation to sex, age, infarct location, as well as CPK levels and time between onset of symptoms and start of treatment. First coronary angiography showed an open vessel in 23/64 patients (36%) of group I and in 12/63 patients (19%) of group II (p less than 0.001). Mechanical recanalization with 3 F catheters could be achieved in 27/41 patients (66%) of group I and with 4 F catheters in 26/51 patients (51%) of group II. In 9/41 patients (22%) of group I and in 18/51 patients (35%) in group II reperfusion took place before mechanical recanalization could be performed or occurred during superselective thrombolysis therapy, when mechanical recanalization failed. Thus, reperfusion rate in group I was 59/64 patients (92%) and in group II 56/63 patients (89%). PTCA was attempted in 55/56 patients in group II with a success rate of 65% and reocclusion rate of 4%. During hospital stay, reocclusion occurred in 10/59 patients in group I (17%) and in group II in 9/55 patients (16%). The patients were divided in those with and without successful angioplasty. Reocclusion was found in 3/36 patients (8%) and 6/17 patients (35%), respectively. Improvement with PTCA of regional and global left ventricular function was observed in patients with anterior myocardial infarction. With combined medical-mechanical recanalization, reperfusion rate can be increased and infarct time shortened, thus, providing the possibility of full revascularization by PTCA, improving coronary blood flow as well as improving global and regional left ventricular function.

Angioplasty, Balloon↗

PubMed2006

Neuropsychological functions in progressive supranuclear palsy, multiple system atrophy and Parkinson's disease.

BACKGROUND: Few studies have compared cognitive functions in multiple system atrophy (MSA), progressive supranuclear palsy (PSP) and Parkinson's disease (PD). AIM: To compare the results of cognitive function tests in the three diseases and examine their relation with the severity of parkinsonism. SETTINGS AND DESIGN: Clinic-based open prospective study. MATERIALS AND METHODS: Global cognitive function tests and tests specific for frontal lobe functions were used in 25 cases of each disease. UPDRS III was used to measure the severity of parkinsonism. STATISTICAL ANALYSIS: ANOVA was done for group comparisons, followed by t-test for independent samples with Bonferroni correction. Pearson's correlation test was done to assess the relation between severity of parkinsonism and cognitive functions. RESULTS: The severity of parkinsonism was worst in PD followed by PSP and least in MSA. Patients with PSP exhibited the worst performance in both sets of cognitive tests. Even though patients with MSA did better than PD in global function tests, they performed worse than PD in some frontal function tests. There was a negative correlation between severity of parkinsonism and scores in cognitive tests in the MSA group but not in others. CONCLUSIONS: Global and frontal dysfunction was worst in PSP. The frontal dysfunction in MSA was more severe than PD, correlated with the severity of parkinsonism and was worse in clinically probable than possible cases of MSA. The severity of cognitive dysfunction in these diseases may be related to the distribution and extent of pathological changes affecting the striato-frontal circuits in them.

Aged↗

PubMed2003

Comparative value of ECG-gated blood pool SPET and ECG-gated myocardial perfusion SPET in the assessment of global systolic left ventricular function.

Both electrocardiographically (ECG) gated blood pool SPET (GBPS) and ECG-gated myocardial perfusion SPET (GSPET) are currently used for the measurement of global systolic left ventricular (LV) function. In this study, we aimed to compare the value of GSPET and GBPS for this purpose. The population included 65 patients who underwent rest thallium-201 GSPET imaging at 15 min after (201)Tl injection followed by planar (planar(RNA)) and GBPS equilibrium radionuclide angiography immediately after 4-h redistribution myocardial perfusion SPET imaging. Thirty-five patients also underwent LV conventional contrast angiography (X-rays). LV ejection fraction (EF) and LV volume [end-diastolic (EDV) and end-systolic (ESV) volumes] were calculated with GBPS and GSPET and compared with the gold standard methods (planar(RNA) LVEF and X-ray based calculation of LV volume). For both LVEF and LV volume, the inter-observer variability was lower with GBPS than with GSPET. GBPS LVEF was higher than planar(RNA) (P<0.01) and GSPET LVEF (P<0.01). Planar(RNA) LVEF showed a slightly better correlation with GBPS LVEF than with GSPET LVEF: r=0.87 and r=0.83 respectively. GSPET LV volume was lower than that obtained using X-rays and GBPS (P<0.01 for both). LV volume calculated using X-rays showed a slightly better correlation with GBPS LV volume than with GSPET LV volume: r=0.88 and r=0.83 respectively. On stepwise regression analysis, the accuracy of GSPET for the measurement of LVEF and LV volume was correlated with a number of factors, including planar(RNA) LVEF, signal to noise ratio, LV volume calculated using X-rays, summed rest score and acquisition scan distance (i.e. the radius of rotation). The accuracy of GBPS for the measurement of LVEF and LV volume was correlated only with the signal level, the signal to noise ratio and the acquisition scan distance. Both GSPET and GBPS provide reliable estimation of global systolic LV function. The better reliability of GBPS and in particular its lower sensitivity to different variables as compared with GSPET favours its use when precise assessment of global systolic LV function is clinically indicated.

Adult↗

PubMed2001

Direct coronary artery perfusion from the left ventricle.

OBJECTIVES: Trends in coronary bypass surgery require less invasive techniques and more conduits. We investigated the ability of direct coronary perfusion from the left ventricle to support regional and global cardiac function. METHODS: A conduit was established between the left ventricle and left anterior descending coronary artery (n = 6) with an interposed Starling resistor that allowed for graded regulation of backward flow. Changes of coronary flow, regional function in the territory of the left anterior descending coronary artery, and reactive hyperemia were studied. In 3 separate dogs, functional tolerance to increased heart rate was tested. In another 3 dogs, left ventricle-left anterior descending and left ventricle-left circumflex coronary artery conduits were established simultaneously (double conduit), and global function was tested. RESULTS: Without flow regulation, flow through the left ventricle-left anterior descending conduit exhibited high peaking (102 +/- 35 mL/min), midsystolic forward flow, and large pandiastolic backward flow (peaking at -47 +/- 22 mL/min). Mean coronary flow and regional function were maintained at 46.0% +/- 7.1% (35.8%-54.2%) and 45.3% +/- 29.1% (-1.8%-74.2%) of their respective normal values. When the Starling resistor was used to regulate backward flow, these values increased to 70.8% +/- 12.5% (56.8%-90.4%) and 70.2% +/- 27.8% (23.6%-107.7%), respectively. Coronary and functional reserve with a left ventricle-left anterior descending conduit were not observed. With the double conduit, global ventricular contractility indexed by end-systolic pressure-volume relation averaged 46% +/- 35% of its normal value. CONCLUSIONS: A left ventricle-coronary artery conduit supplied approximately 45% of normal blood flow and regional function, and both were improved by regulation of backward flow. Therefore, a conduit from the left ventricle to an epicardial vessel could serve as a rapidly deployable means of revascularizing totally occluded coronary vessels for which suitable natural conduits are not available.

Anastomosis, Surgical↗

PubMed2006

The relationship between perceived and objective cognitive functioning in multiple sclerosis.

The relationship between perceived cognitive functioning and objective cognitive functioning was studied in 221 patients with multiple sclerosis. Perceptions of global cognitive functioning as well as perceptions of performance on specific cognitive tests were assessed. Patients' perceptions of global cognitive functioning in their daily lives were unrelated to their objective performance on the full cognitive test battery. However, patients' perceptions of their performance on specific tasks correlated with their objective performance on those tasks, even though they underestimated their performance on these tasks. The present study also evaluated predictors of patients' perceived cognitive functioning. Depression, anxiety, fatigue, and level of disability predicted perceptions of global cognitive functioning, whereas objective cognitive performance did not. These results add to our understanding of patients' expressed concerns regarding their cognitive functioning in the wake of multiple sclerosis, suggesting that such concerns should be interpreted with caution by clinicians.

Adult↗

PubMed2004

Left ventricular long-axis function is reduced in patients with rheumatic mitral stenosis.

Left ventricular long-axis function evaluated by M-mode or tissue Doppler echocardiography has been shown to be useful indexes of left ventricular systolic function; however it has not been evaluated in patients with mitral stenosis. We examined the left ventricular long-axis function of the patients with pure mitral stenosis and normal global systolic function as assessed by fractional shortening of the left ventricle (LV). Fifty-two patients with pure mitral stenosis and twenty-two healthy controls were evaluated by echocardiography. Although there was no statistically significant difference in global systolic function, M-mode derived systolic motion of the septal side and (12 +/- 3 vs 14.4 +/- 1.5 mm, P = 0.016) the lateral side of mitral annulus (13.2 +/- 3 vs 16.8 +/- 2 mm, P = 0.001) were both significantly lower in the patients with mitral stenosis than control subjects. Similarly tissue Doppler systolic velocity of the septal annulus (7.6 +/- 1.1 vs 10.4 +/- 3.2 cm/s, P = 0.03) and lateral mitral annulus (7.6 +/- 1.1 vs 10.4 +/- 3.2 cm/s, P = 0.003) were also significantly lower in patients with mitral stenosis than in controls. There was a statistically significant correlation between septal annular motion and annular velocity (r = 0.643, P = 0.002). Septal annular motion and annular velocity were also correlated with left atrial ejection fraction (r = 0.338, P = 0.005 and r = 0.676, P = 0.001, respectively). Thus, patients with mitral stenosis had significantly impaired long-axis function evaluated by M-mode or tissue Doppler echocardiography despite normal global systolic function.

Adult↗

PubMed1998

The global turning probability density function for motile bacteria and its applications.

The angular turning probability density distribution for motile bacteria is usually measured in local coordinates and is therefore inconvenient for global analyses of the chemotactic bacterial migration. In this paper we present analytical derivations that convert the local angular turning probability density distribution into a global one. The explicit expression of a reduced global turning probability density function for motile bacteria was derived and its relevant properties were investigated. Depending on the angle variable being intergrated and the integration range, three types of cosine moments were separately defined and studied. Some statistical indices and parameters such as the directional persistence, persistence number, and one-dimensional reversal probability were found to be embedded in the various moments of the reduced global turning probability density function. Applications of the reduced global turning probability and its integrated moments to a three-dimensional cell balance equation in an axisymmetric system were also discussed.

Bacterial Physiological Phenomena↗

PubMedDate not supplied

Prospective assessment of sexual function in women treated for recurrent major depression.

Although multiple factors may influence the sexual function of depressed women over the course of treatment, the independent contributions of these factors are poorly understood. The current study examined the effects of depression, SSRI treatment, and sexual partner availability on women's sexual function. The sexual function of 68 recurrently depressed women was assessed at 3-month intervals over a 1-year course of treatment with interpersonal psychotherapy with or without adjunctive SSRI treatment. Random regression models assessing changes in sexual function were conducted to test the effects of three time-dependent covariates: depression symptom scores, sexual partner availability, and SSRI medication status. Controlling for the other variables, depressive symptoms were associated with decrements in sexual desire, sexual cognition/fantasy, sexual arousal, orgasmic function, and global evaluations of sexual function. SSRI treatment was associated with orgasmic difficulty only. The availability of a sexual partner was associated with increased sexual arousal, orgasmic function, and sexual behavior. Among treatment remitters, patient reports of severe sexual dysfunction did not change over the course of treatment, although mild improvement was observed in patients' global assessment of the quality of their sexual function. This report illustrates the prevalence and persistence of sexual dysfunction in this sample, and highlights the importance of monitoring both pharmacologic and psychosocial variables that can affect the sexual function of recurrently depressed women throughout the course of treatment.

Adult↗

PubMedDate not supplied

Validation of a simple isotopic technique for the measurement of global and separated renal function.

Schlegel and Gates described an isotopic method for the measurement of global and separated glomerular filtration rate (GFR) and effective renal plasma flow (ERPF) based on the determination by scintillation camera of the fraction of the injected dose (99mTc-DTPA-[131I]hippuran) present in the kidneys 1-3 min after its administration. This method requires counting of the injected dose and attenuation correction, but no blood or urine sampling. We validated this technique by the simultaneous infusion of inulin and polycyclic aromatic hydrocarbon (PAH) in patients with various levels of renal function (anuric to normal). To better define individual renal function we studied 9 kidneys in patients either nephrectomized or with a nephrostomy enabling separated function measurement. A good correlation between inulin, PAH clearance, and isotopic GFR-ERPF measurement for both global and separate renal function was observed.

Glomerular Filtration Rate↗

PubMed2005

Global ischemia downregulates the function of metabotropic glutamate receptor subtype 5 in hippocampal CA1 pyramidal neurons.

Within the hippocampus, electrophysiological and immunohistochemical studies showed that metabotropic glutamate receptor subtype 5 (mGluR5) is the major postsynaptic mGluR expressed in CA1 pyramidal neurons. To better understand the role of mGluR5 in ischemia-induced neuronal death, whole-cell patch-clamp recordings using hippocampal slices were performed to investigate the functional change of mGluR5 in CA1 pyramidal neurons following transient global ischemia. Our results indicated that 6 to 24 h after global ischemia, mGluR5-induced cationic currents and mGluR5-mediated enhancement of NMDA-evoked currents in CA1 pyramidal neurons were significantly reduced. Further TaqMan real-time quantitative RT-PCR assay showed that mGluR5 mRNA expression in hippocampal CA1 region or single CA1 pyramidal neurons was significantly downregulated following ischemic insults. The present study suggests that transient global ischemia downregulates mGluR5 function of CA1 pyramidal neurons by decreasing mGluR5 mRNA and that the resulting reduced mGluR5-mediated excitotoxicity could contribute to the survival of CA1 pyramidal neurons after ischemic insult.

Animals↗

PubMed2001

Perfusion and functional abnormalities outside the septal region in patients with left bundle branch block assessed with gated SPECT.

BACKGROUND: The presence of a left bundle branch block (LBBB) pattern on the electrocardiogram may frequently lead to perfusion defects in the septum not necessarily due to ischemic heart disease, but probably due to abnormal septal wall motion. The introduction of gated single photon emission computed tomography (SPECT) allows the evaluation of myocardial perfusion and function in one study. Accordingly, we analysed perfusion and function and the relation between perfusion and regional function in the septal region in patients with a LBBB without evidence of a previously sustained myocardial infarction. METHODS: We selected 37 patients with a LBBB without a history of a previous myocardial infarction, which was confirmed by echocardiography and/or coronary angiography. All patients underwent technetium-99m tetrofosmin gated SPECT myocardial imaging. Twelve control patients with a low likelihood of coronary artery disease and a normal technetium-99m tetrofosmin gated SPECT myocardial perfusion scintigram were selected as a reference population. The left ventricle (LV) was divided into 18 segments, which were scored for perfusion and function (wall motion and wall thickening) on a 4-point scale. RESULTS: The average LV end-diastolic volume was higher and the average LV ejection fraction was lower in patients with LBBB as compared to controls (142+/-90 vs. 81+/-18 ml, and 48+/-19 vs 62+/-7%, p=0.03 and p=0.02, respectively). Not only in the septum, but also in the other segments, reduced myocardial perfusion and abnormal wall motion/wall thickening was observed in the patients with LBBB (p<0.0001 vs controls). Patients with LBBB showed no correlation between perfusion and function in the septum, and between perfusion in septum and global LV function (r=0.21, p=0.2; r=0.10, p=0.6, respectively). Conversely, a good correlation was found between perfusion and function, either regional or global, in the remote segments (both r=0.79, p<0.0001). CONCLUSIONS: We conclude that patients with LBBB without a previous myocardial infarction show cardiomyopathic changes with perfusion and wall motion abnormalities, involving the entire left ventricle. The severity of diminished septal perfusion is not directly associated with the severity of septal wall motion abnormalities or global LV function. However, in the myocardial segments remote from the septum, reduced perfusion is closely associated with functional abnormalities.

Bundle-Branch Block↗

PubMed1987

Early and late global and regional left ventricular function after experimental transmural myocardial infarction: relationships of regional wall motion, wall thickening, and global performance.

Experimental myocardial infarction of the posterolateral wall of the left ventricle was produced in dogs by injecting 80 micron microspheres into the left circumflex coronary artery to determine changes in regional myocardial function after infarction, to examine how the changes in regional myocardial function relate to the changes in global left ventricular function, and to examine the relationship between regional wall motion and wall thickening after myocardial infarction. Serial measurements of global ventricular and regional myocardial function were made in six dogs before and during 20 days after infarction, with the use of M-mode echocardiography and chronic Swan-Ganz catheter implantation. One hour after infarction, stroke volume index had decreased 49% from baseline, percent fractional shortening had decreased 52%, lateral wall motion had decreased 80%, and lateral wall thickening had decreased 100%. By 6 days after infarction, stroke volume index had increased 41% from its low point, percent fractional shortening had increased 34%, and lateral wall motion had increased 100% toward but not to baseline. Lateral wall thickening did not return following infarction. Peak and end-systolic circumferential wall stresses and systemic arterial blood pressure remained stable. End-systolic diameter increased acutely (36%) after infarction and did not change during the 20-day time period, while end-diastolic diameter gradually increased, resulting in the increase in percent fractional shortening. In conclusion, after posterolateral wall infarction, wall motion can return without an improvement in regional myocardial function, presumably because the infarcted region stiffens, allowing it to be pulled inward.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed2004

Testing the goodness-of-fit of a multifaceted preventive intervention for children at risk for conduct disorder.

OBJECTIVE: To determine the importance of parents' global adaptive functioning as a predictor of participation rate and subsequent child social competence outcome in 3 program components of an evidence-based, multifaceted, preventive intervention for at-risk children. METHOD: Families of program children (n = 124, mean age 6.6 years at recruitment) were offered 3 program components that continued for 3 years: a 6-week summer program, a biweekly family program that included concurrent parent and child education and skills training groups, and a flexibly tailored home visitation family support program. We used structural equation modelling to test hypotheses about the effects of parental characteristics on program attendance in each of the program components over 3 years, as well as their relation to children's social competence. RESULTS: Predictors of attendance included child IQ, socioeconomic status (SES), and single-parent status for some components but not others, depending on parents' global adaptive functioning. Predictors of child social competence outcome were mediated by attendance in specific program components and were dependent on parent global adaptive functioning. Some components contributed decisively to social competence outcomes, and others did not, despite subjects' participation. CONCLUSIONS: Common family characteristics (that is, child IQ, SES, and single-parent status) predict program attendance differently, depending on parents' global adaptive functioning. Parents' global adaptive functioning determined whether attendance in specific program components mediated children's social competence. In this preventive intervention, as in clinical practice, only knowledge of the goodness-of-fit between participant characteristics and program attributes can ensure optimum benefit.

Adaptation, Psychological↗

PubMed2006

Multisegment and halfscan reconstruction of 16-slice computed tomography for assessment of regional and global left ventricular myocardial function.

RATIONALE AND OBJECTIVES: We sought to prospectively compare multisegment and halfscan reconstruction of 16-slice computed tomography (CT) for the assessment of regional and global left ventricular myocardial function with magnetic resonance imaging (MRI) as the reference standard. MATERIALS AND METHODS: Forty-two patients underwent CT with 16 x 0.5-mm detector collimation. Electrocardiogram-gated reconstructions were generated with multisegment reconstruction (using up to 4 segments correlated with the raw data of up to 4 heartbeats) and standard halfscan reconstruction. Steady-state free-precession cine MRI was acquired within 24 hours. RESULTS: More normal myocardial segments were identified correctly with multisegment (95%, 620/656) compared with halfscan reconstruction (88%, 582/656) of CT (P < 0.001). Also, the accuracy (92% [657/714] vs. 87% [620/714]) and rate of nondiagnostic segments (0% vs. 5% [33/714]) were significantly better when using multisegment reconstruction (P < 0.001). The image quality with multisegment reconstruction was significantly superior to that achieved with halfscan reconstruction (P < 0.001). In the assessment of global left ventricular function, multisegment and halfscan reconstruction of CT showed high correlations for all parameters with MRI, whereas Bland-Altman analysis revealed smaller limits of agreement for assessment of myocardial mass with multisegment reconstruction (P = 0.025), but no significant differences between both reconstruction techniques in the measurement of left ventricular volumes as compared with MRI. CONCLUSIONS: Multisegment reconstruction of 16-detector row CT improves image quality and assessment of regional wall motion compared with standard halfscan reconstruction.

Adult↗

PubMed1991

[Reference values of global and regional myocardial function for stress echocardiography].

Two-dimensional echocardiography has become a sensitive method to differentiate between normal and pathological myocardial function during exercise. Examining 50 healthy volunteers we determined normal values for global and regional left-ventricular function during bicycle exercise. Ejection fraction increased from 59 +/- 10% at rest to 85 +/- 7% at 210 watts workload, endsystolic volume decreased from 22.1 ml/m2 at rest to 7.1 ml/m2 at 210 watts. Enddiastolic volume showed a tendency to decrease from 55 +/- 21 ml/m2 at rest to 45 +/- 23 ml/m2 at 210 watts. Quantitative analysis showed an extended distribution both for Centerline- and Radiant-Method, during exercise Centerline-Method was superior. Two-dimensional echocardiography is useful for assessment of global and regional myocardial function during exercise. Decrease of ejection fraction or increase of endsystolic volume seems to be a pathological marker. Enddiastolic volume is a less useful parameter for evaluating left-ventricular function during stress. Quantitative analysis of left ventricular wall motion can be applied with restrictions.

Adult↗

PubMed1999

Modified ultrafiltration improves global left ventricular systolic function after open-heart surgery in infants and children.

OBJECTIVES: Modified ultrafiltration increases blood pressure and cardiac index following open-heart surgery in children, but it is unclear if this is secondary to an improvement in global left ventricular function. A previous report has suggested that left ventricular systolic function as assessed in a single chord is improved by ultrafiltration (Davies MJ, Nguyen K, Gaynor JW, Elliott MJ. Modified ultrafiltration improves left ventricular systolic function in infants after cardiopulmonary bypass. J Thorac Cardiovasc Surg 1998;115:361--370). The prominent vascular actions of modified ultrafiltration necessitate left ventricular assessment using load-independent indices of systolic and diastolic function. METHODS: In 22 consecutive infants and children undergoing open-heart surgery, left ventricular function was assessed following bypass and then 10 min later. Sixteen children (median weight 8.1 kg) underwent modified ultrafiltration during this period, the remainder (median weight 7.3 kg) were controls for spontaneous recovery without ultrafiltration. Real-time pressure-volume loops, with transient inferior caval vein snaring were generated from conductance and microtip pressure catheters inserted through the LV apex. From these, load-independent (slope of the end-systolic pressure-volume [Ees] and end-diastolic pressure-volume [Eed] relationships) and load-dependent (Pmax, maximum LV pressure; Ped, end-diastolic LV pressure; maximum [dP/dtmax] and minimum [dP/dtmax] time derivatives of LV pressure; tau, time constant of isovolumic relaxation) indices of left ventricular function were measured. RESULTS: Haemoconcentration was achieved in all modified ultrafiltration patients, median increase in haematocrit 34% (interquartile range 21%, 42%), final haematocrit 0.40 (0.35, 0.41). Ees increased 58% (9, 159, P = 0.005). The changes in Eed, Pmax, Ped, dP/dtmax, dP/dtmin, and tau were not significantly different from the control group. CONCLUSION: Modified ultrafiltration improves global left ventricular systolic function in infants and children following open-heart surgery.

Cardiac Surgical Procedures↗

PubMed1999

MELISSA: global control strategy of the artificial ecosystem by using first principles models of the compartments.

MELISSA is a micro-organisms based ecosystem conceived as a tool for understanding the behaviour of artificial ecosystems, and developing the technology for a future biological life support system for long term space mission. The driving element of MELISSA is the recovering of oxygen and edible biomass from waste (faeces, urea). Due to its intrinsic instability and the safety requirements of manned missions, an important control strategy is developed to pilot this system and to optimize its recycling performance. This is a hierarchical control strategy. Each MELISSA compartment has its local control system, and taking into account the states of other compartments and a global desired functioning point, the upper level determines the setpoints for each compartment. The developed approach is based on first principles models of each compartment (physico chemical equations, stoichiometries, kinetic rates, ...). Those models are used to develop a global simulator of the system (in order to study the global functioning). They are also used in the control strategy, which is a non linear predictive model based strategy. This paper presents the general approach of the control strategy of the loop from the compartment level up to the overall loop. At the end, some simulation and experimental results are presented.

Biomass↗