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Biomedical subjects

M Duvelleroy

Publications and source records attributed to M Duvelleroy.

At least 37 records · Page 2Linked to original sources
PubMed1982

[Transcapillary fluid exchanges. A program in Basic].

Transcapillary fluid exchanges are analysed with the Wiederhielm's model programmed in this study in Basic language. The physiological variable which are taken in account are: arterial and venous capillary pressures, interstitial pressure and the colloid osmotic pressure of plasma and tissue proteins. This model shows the relationship between filtration, reabsorption, plasma leakage and the lymph flow. Edema resulting from venous and lymphatic obstruction or from a decrease in plasma oncotic pressure are simulated.

Blood Pressure↗
PubMed1981

[Uptake of oxygen in the lung: a program for the microcomputer].

Written for pedagogic purpose, this paper describes a Basic program of the alveolar diffusion and shunt effect, for personal computer. Equations and algorythms are described first. Then the program is explained in great detail in order to be easily implemented. Nine typical situations are stimulated and discussed.

Computers↗
PubMed1981

[Ventilation perfusion distribution: a program for personal computer (author's transl)].

Ventilation perfusion inequality, is analysed with the help of a program written in Basic language, easily implemented on a personal computer. For a gas exchange unit, the main equation describes a mass balance for oxygen, assuming absence of diffusion barrier. The use of a large number of these units allows for calculation of the resulting arterial PO2 in case of abnormal ventilation blood flow distribution. Several simulations are made to study the effect of local variations of VA/Q ratio, and oxygen inhalation upon arterial PO2.

Computers↗
PubMed1979

Effect of an increase in HbO2 affinity on the calculated capillary recruitment of an isolated rat heart.

The effect of an increase in hemoglobin O2 affinity on myocardial O2 delivery was studied in a blood perfused working rat heart preparation. In a first series of experiments P50 (PO2 for which saturation is 50%) was lowered by use of carbon monoxide. The heart was alternatively perfused with the blood sample of P50 = 32 mm Hg and the blood sample of P50 = 17 mm Hg. O2 capacity of both samples was kept the same by appropriate hemodilution. In a second serie of experiments change of P50 was obtained by the use of adult human erythrocytes containing hemoglobin creteil with a P50 of 13.6 mm Hg. As P50 decreased from 25 to 10 mm Hg, coronary sinus PO2 (PcsO2) diminished from 26 +/- 2 to 18 +/- 2 mm Hg (-29 +/- 2%), coronary sinus O2 content (CcsO2) increased by 15 +/- 3%, myocardial oxygen consumption did not change significantly. The percentage of increase of coronary flow was 23 +/- 4%. Analysis of these results with a simple mathematical model of O2 delivery suggest that increase in HbO2 affinity is corrected by a simultaneous increase in coronary flow and capillary recruitment.

Animals↗
PubMed1979

[Theoretical, experimental and clinical effects of variations in hematocrit during hemodilution].

By decreasing both viscosity and maximum oxygen capacity, a fall in hematocrit has two opposing effects on oxygen transport. The resultant of these effects was studied using a mathematical model representing the circulatory system and the oxygen transport system. This simulation showed that hemodilution decreased mean aortic pressure, increased central venous pressure and cardiac output. Oxygen supply to the tissues was maximum at a hematocrit of 30 p. cent. Blood volume was an essential parameter. These theoretical concepts of an optimum hematocrit of 30 p. cent were confirmed in the isolated rat heart perfused by blood with varying hematocrits. A clinical study in general surgery involving 307 patients where the hematocrit was reduced to below 32 p. cent by replacing blood loss by Ringer lactate or a fluid gelatin type solution, showed the good tolerance of normovolaemic hemodilution when used carefully, and its value in the prevention of post-operative thrombo-embolic disease.

Adult↗
PubMed1978

Computer analog simulation of a model for the regulation of ago-antagonistic couples.

A system of quadratic differential equations is proposed within the framework of 'non-linear mechanics', but also outside this framework in respect of certain features, and it is used with a view to formalising a feedback control system. The model helps to simulate states of balance or imbalance within an ago-antagonistic couple and to suggest methods for correcting the imbalances, which do not require modification of the parameter space. Its possibilities of synchronic or diachronic functioning are emphasised. The model may apparently be used for the construction of similar models which include several ago-antagonistic couples. Finally, the aims of such a model, which could be considered as an 'action' model, are defined; its place would be assigned midway between a black-box system and 'knowledge' models.

Computers↗
PubMed1978

Hemoglobin Creteil: oxygen transport by erythrocytes. In-vitro and in-vivo studies in a high oxygen-affinity mutant hemoglobin.

Hemoglobin Hb) Creteil alpha2beta(2)89 (F5) Ser leads to Asn is a high oxygen-affinity variant that has a low cooperativity, a decreased Bohr effect, and does not interact with diphosphoglycerate (DPG) (1). This hemoglobin variant was silent by routine electrophoresis. Careful analyses of the oxygen dissociation curves of erythrocytes, determined at varying pH and Pco2 in fresh and DPG-depleted cells, gave extensive information on the abnormal function of the mutant hemoglobin. From the O2 dissociation curves of the erythrocytes of the heterozygous subject it appeared that Hb Creteil is inappropriate for O2 transport to the tissues because it remained completely saturated with O2 at normal physiologic levels of Po2. In-vivo measurements showed that only one half of the total hemoglobin present actually participated in oxygen transport. Polycythemia should therefore be maintained within clinically tolerable limits because it helps to keep arterial Po2 and Pvo2 close to their normal values and thus protects the individual from a permanent increase in blood flow.

Adult↗
PubMed1971

[Oxygen transport].

Explore the source record for details and available documents.

Blood Circulation↗
PubMedDate not supplied

Red blood cell aggregation and microcirculation in rat cremaster muscle.

Using intravital microscopy of the rat cremaster muscle, we studied the effects of changing red blood cell (RBC) aggregation on RBC arteriolar velocity and perfused capillary density (PCD). To modify RBC aggregation, 2 and/or 10% dextran (molecular weights 40,000, 70,000 or 480,000) or fresh rat plasma was infused into adult male rats via a normovolemic hemodilution procedure. The high-molecular-weight dextrans (70,000 and 480,000) both induced RBC hyperaggregation associated with similar dose-dependent decreases in RBC arteriolar velocity (30 and 40% for dextran concentrations of 2 and 10%, respectively) and in PCD (35 and 37%, respectively, for the two concentrations). Conversely, with 40,000 molecular weight dextran or plasma, we observed a 30% increase in RBC arteriolar velocity, but no change in PCD or hyperaggregation. Intravenous injection of the antiaggregating drug troxerutin (10(-3) M), either before or after 2% dextran 70,000, significantly inhibited the effects of this dextran on RBC arteriolar velocity and on PCD. We conclude that RBC hyperaggregation can lead to changes in both arteriolar velocity and PCD and may, therefore, impair tissue oxygenation.

Animals↗
PubMedDate not supplied

[Analytical and analogical study of a model of the adrenal-postpituitary function (author's transl)].

After an analyitical study of mathematical models connected with osmotic or volemic regulations, and the mention of its contribution to the therapeutic act, the authors approach the stimulation, by the mean of an analogical computer, of the complete and non-linear model which associates both types of regulation. So it is possible to attempt to determine the level of adrenal and vasopressin actions according to: 1 degree the sum of the agonistic effects and the difference of their antagonistic effects; 2 degrees the perturbations brought to the system; 3 degrees the parametric values of the model. Theoretical and empirical curves seem to be in favour of such a formulation.

Adrenal Cortex↗
PubMedDate not supplied

[Autotransfusion].

The risk of contracting certain disorders following a blood transfusion is currently becoming worrisome not only for physicians who are aware of this problem, but also for patients who, with increased media attention on AIDS, are more afraid of this potential risk than of the surgical or anesthetic risks. In fact, hepatitis constitute the major risk involved in homologous transfusion since some 60,000 cases are reported each year in France. Prevention of transmission of disease by blood transfusion is based on decreasing homologous transfusions and especially by saving blood. Indeed, when surgery is planned, units of the patient's blood can be obtained in the weeks prior to it to be used during the operation or the immediate follow-up period. In case of emergency surgery, blood is collected preoperatively making it possible to obtain hemodilution during surgery and an autotransfusion if necessary at the conclusion of the procedure. Finally, there are methods to recover blood at the actual site of the surgical procedure.

Acquired Immunodeficiency Syndrome↗
PubMedDate not supplied

[Simulation of transcapillary exchange of liquids].

The transcapillary exchanges of liquids between vascular and interstitial sections can be described with the help of a mathematical model describing variation in filtration, reabsorption, plasmatic flux and lymphatic flow in relation to the different active pressures, that is to say the arteriolar and venular pressures, the oncotic pressures of the proteins, and interstitial pressure. Also taking into account the modifications of the volemia in relation to blood loss and perfusions, modifications of the essential haemodynamic variables and diuresis, it is possible to reproduce various situations following the reduction in venous or lymphatic return, hypovolemia, and hypoproteinemia. The advantages in these simulations is demonstrated by the example of a blood depletion, compensated or otherwise, as follows: volemia, proteinemia, lymphatic flow. These simulations permit us to follow the sequence of events accompanying haemodilution, and to assess the qualities of a plasmatic substitute: oncotic strength, demi-vie, effect on the extravascular mobilisation of proteins. They also provide a reflexion tool permitting a better comprehension of transcapillary exchanges and the optimisation of strategies of vascular refill.

Body Fluids↗
PubMedDate not supplied

Cardiac effects of phytic acid induced high P50 with free and limited coronary blood flow.

A blood preparation with a large increase in P50, obtained by a new technique to encapsulate inositol hexaphosphate (IHP) in erythrocytes was evaluated on an isolated heart model. Each heart was alternatively perfused with control stored human blood (P50 = 2.12.+/- 0.9 mmHg) and IHP-treated human blood (P50 = 42.5 +/- 9.33 mmHg). Changes of perfusates were performed when coronary blood flow (CBF) was free and adapted to a constant perfusion pressure (FREE CBF). Changes of perfusates were also performed at a constant but restricted CBF corresponding to 55% of basal value (RESTRICTED CBF). Both bloods were oxygenated and equilibrated to achieve the same acid-base balance, arterial PO2 and O2 content. When CBF was not restricted, switching from control blood to IHP-treated blood, induced a decrease in CBF (-23%), an increase in coronary sinus PO2 (57%) and a decrease in coronary sinus O2 content associated with an increase in myocardial O2 consumption (14%). These metabolic changes were associated with a decrease in left ventricular developed pressure (LVDevP) (-15%) and its maximal positive derivative (-12%). When CBF was restricted, switching from control blood to IHP-treated blood, induced an increase in perfusion pressure (59%). This vasoconstriction was associated with the same changes in the blood gas measurements as those observed when CBF was not restricted, while LVDevP increased significantly (7%). It is concluded that the beneficial effects on myocardial metabolism from the increase in P50 with IHP, are lessened by the cardiodepressive effect of the blood preparation which is predominant when CBF is not restricted.

Animals↗
PubMedDate not supplied

[Hemodilution in persistent postphlebitic ulcers].

By definition, rebel post-phlebitic ulcers are very difficult to cure. However, it has recently been apparent that the classic treatments associated with permanent normovolemic haemodilution are more effective. Two research procedures have been implemented simultaneously to try and explain this beneficial effect of haemodilution, one based on an experimental study of isolated rabbit hearts, and the other on a theoretical model of the blood-flow at capillary level. These studies lead us to believe that a better distribution of tissular oxygenation might be one of the mechanisms responsible for the beneficial effect of permanent normovolemic haemodilution in treatment of rebel post-phlebitic ulcers.

Animals↗