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Biomedical subjects

G Teyssier

Publications and source records attributed to G Teyssier.

At least 37 records · Page 2Linked to original sources
PubMed1993

Fetal central blood flow alterations in human fetuses with umbilical artery reverse diastolic flow.

Blood flow velocimetry studies in animal fetuses with reverse diastolic flow in the umbilical artery have shown marked changes in the fetal central circulation characterized by a retrograde diastolic flow in the descending aorta, and as far as the aortic arch, along with a significant forward diastolic flow in the arteries going to the brain. Documentation and the implications of this phenomenon in human fetuses, to date, have not been reported. Doppler echographic evaluations of the diastolic patterns in the umbilical artery, descending aorta, the aortic arch, and the common carotid artery were performed on 5 fetuses in whom reverse diastolic flow was observed in the umbilical artery. In all five cases reverse diastolic flow was observed not only in the umbilical artery but also in the aortic arch. In the carotid artery, however, a forward diastolic flow was always recorded. It can be concluded, by inference, that in these fetuses, the area of lowest resistance was no longer the placenta, as seen in normal conditions, but the cerebral circulation. Furthermore, in four fetuses the retrograde component of the flow profiles was more prominent in the aortic arch compared with the descending aorta, suggesting that, in diastole, blood was coming from the pulmonary artery through the ductus arteriosus.

Adult↗
PubMed1993

Quantitative assessment of circulatory changes in the fetal aortic isthmus during progressive increase of resistance to umbilical blood flow.

BACKGROUND: This study investigated the effects of impairment to placental flow on flow patterns through the aortic isthmus because in the fetus, this vascular segment is the link between the parallel vascular systems perfused by the left and right ventricles. METHODS AND RESULTS: A progressive increase in resistance to blood flow through the placenta was created in seven exteriorized fetal lambs by mechanical umbilical vein compression. Blood flows were measured in the ascending aorta, pulmonary artery, aortic isthmus, and umbilical artery at baseline and at each compression level. The severity of the levels of compression was determined by changes in the flow profile through the umbilical artery. An increase in placental resistance causing a fall in umbilical blood flow of approximately 50% was associated with a retrograde diastolic flow through the aortic isthmus even though the diastolic flow through the umbilical artery remained forward. Because of the systolic predominance, however, the net flow in the isthmus was forward. With a more severe increase in placental resistance corresponding to a decrease of 75% in umbilical blood flow, the net flow through the isthmus approached zero. A strong positive correlation was found between the umbilical blood flow and the net flow through the aortic isthmus (r = .89). CONCLUSIONS: Variations in Doppler blood flow velocity waveforms and integrals of the aortic isthmus can be used as a sensitive indicator of the state of the umbilical circulation.

Animals↗
PubMed1993

Effects of increased resistance to umbilical blood flow on fetal hemodynamic changes induced by maternal oxygen administration: a Doppler velocimetric study on the sheep.

A fetal lamb model was used to investigate whether the effects of maternal O2 administration on fetal blood gases and hemodynamics were modified when the fetoplacental circulation was compromised by stepwise compression of both umbilical veins. At basal state, O2 administration increased O2 saturation (SaO2) and the pulsatility index (PI) of the carotid artery Doppler wave form (p < 0.01). The first compression decreased left ventricular output (-21 +/- 16%, mean +/- 1 SD, p < 0.01) and umbilical mean velocity (-22 +/- 28%, p < 0.01) but did not modify carotid pH, SaO2, or the PI in any of the arteries studied. At this level of compression, O2 administration increased carotid SaO2 (p < 0.01) but did not affect carotid PI. After a second compression, left ventricular output and umbilical mean velocity were even more reduced [-39 +/- 21% (p < 0.01) and -53 +/- 23% (p < 0.01), respectively]. With this compression, carotid pH, SaO2, and PI decreased, whereas umbilical and descending aorta PI increased. O2 administration at this level of compression increased carotid SaO2 (p < 0.01) but did not modify carotid PI. Throughout the three stages of the experiment, O2 administration did not affect umbilical PI, descending aorta PI, or umbilical mean velocity. A good linear relationship (r = 0.77, p < 0.001) was demonstrated between left ventricular O2 delivery and carotid PI. Thus, at basal state, O2 administration induced velocity changes compatible with an increase in cerebral vascular resistance.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1993

[Citrullinemia: management and clinical course. Apropos of a familial case].

The authors report two cases of citrullinemia in siblings which add to 68 observations from the literature. They overview the clinical presentation, diagnosis and therapeutic management of the disease. The prognosis of severe neonatal form remains poor but an early adequate management may contribute to an acceptable outcome.

Amino Acid Metabolism, Inborn Errors↗
PubMed1992

[Abdominal aortic aneurysm and Bourneville's tuberous sclerosis].

The authors report on a case of tuberous sclerosis diagnosed in the neonatal period on the basis of intracardiac tumor, rib anomalies and cerebral calcifications. At 4.5 months of age the infant presented acute abdominal pains which led to the discovery (ultrasound identification confirmed by CT scan) of a giant ectasia of the whole abdominal aorta. The infant died 2 days later from the rupture of this aortic aneurysm.

Aortic Aneurysm, Abdominal↗
PubMed1992

[Non traumatic acute suppurative mediastinitis].

Acute mediastinitis is uncommon. When it occurs, it usually follows an esophageal perforation or thoracic surgery. We report on a case of a 2-year-old girl with non traumatic mediastinitis secondary to a pharyngitis, due to Staphylococcus aureus. The anatomic pathways that connect the cervical region with the mediastinum explains how the infection can spread within the cervicothoracic spaces. Knowledge of this anatomy is also important in evaluating the possible causes of symptoms and signs in this area, and the possible complications of infections in these regions. The treatment associates antibiotics and drainage of the abscess by either surgical procedure or computed tomography guided selective needle aspirations.

Acute Disease↗
PubMed1992

Cardiac two-dimensional imaging and reference values for blood flow velocities in the ovine fetus.

Since the ovine model is the most commonly used for foetal haemodynamic investigation it was felt important 1) to investigate the technical difficulties involved with ultrasound fetal cardiac imaging in this species and 2) to establish normal reference values for ovine cardiac and umbilical blood flow velocity measurements. Both two-dimensional and pulsed Doppler techniques were used for this assessment in 25 unsedated ewes. All morphological features described in human features to identify the ventricular cavities could be found in the ovine fetus with the two-dimensional echocardiogram. Specific differences included a flatten thorax as visualized from the lateral position, the mesocardial position of the heart, and a large left azygos vein behind the left atrium draining blood into a dilated coronary sinus. The mean peak velocities (cm/sec) of the early diastolic wave (E) and the atrial wave (A), along with their calculated ratio, were not statistically different between the two atrio-ventricular valves (E: 30.6 +/- 6.6, 31.2 +/- 6.1; A: 43.0 +/- 8.3, 41.6 +/- 8.0; E/A: .72, .76 for mitral and tricuspid valves respectively). A significant difference was observed between the acceleration times of the blood ejected into the aorta and the pulmonary artery, with the time interval being shorter in the pulmonary artery (Aorta: 0.052 +/- 0.011; Pulmonary artery: 0.037 +/- 0.009 s). A mean pulsatility index of the umbilical artery of 0.89 was recorded. The data recorded in this study should serve as a reference base for further non-invasive studies of the ovine foetal circulatory system using the ultrasound technique.

Animals↗
PubMed1991

Diastolic circulatory dynamics in the presence of elevated placental resistance and retrograde diastolic flow in the umbilical artery: a Doppler echographic study in lambs.

To evaluate the effects of elevated placental resistance on the diastolic blood flow in the main arteries of the fetus, placental resistance was mechanically increased in six exteriorized lambs. A string was inserted into the exposed section of the umbilical cord and placed around the veins isolating them from the arteries. Doppler flow velocities waveforms were measured by placing a lightweight acoustic bag on the umbilical cord. Placental resistance was increased by tightening the string until retrograde diastolic flow was observed in the umbilical artery. All measurements were obtained within 10 minutes. Heart rate, PO2, PCO2, and pH before umbilical vein compression were 177 +/- 24 beats/min, 16.4 +/- 1.8 mm Hg, 42.5 +/- 4 mm Hg, and 7.3 +/- 0.05, respectively, and 112 +/- 38 beats/min, 5.9 +/- 1.5 mm Hg, 56.6 +/- 7.0 mm Hg, and 7.2 +/- 0.05, respectively, after umbilical vein compression. The patterns of diastolic flow observed after compression were descending aorta, retrograde; aortic arch, retrograde; ascending aorta, bidirectional; cephalic aorta, forward, which were quite different from their respective baseline patterns. It is concluded that the appearance of reverse diastolic flow in the umbilical artery indicates that (1) the lowest vascular resistance in the fetal circulatory network is no longer at the placental but at the cerebral level, and (2) preplacental blood with low oxygen content from the descending aorta and pulmonary artery is being shifted toward the brain.

Animals↗
PubMed1991

Closure of the ductus arteriosus: determinant factor in the appearance of transient peripheral pulmonary stenosis of the neonate.

We speculated that a relationship may exist between transient peripheral pulmonary stenosis and the closure of the ductus arteriosus. Fifty preterm infants had pulmonary artery and ductal color Doppler flow velocity assessments performed before and after closure of the ductus arteriosus. No flow turbulence or increase in velocity was observed immediately after birth, although a significant discrepancy in size was observed between the main pulmonary artery and its two branches. After closure of the ductus, 15 infants had signs of transient peripheral pulmonary stenosis of the left pulmonary artery in association with a significant decrease of diameter at the origin of the same artery. In all 50 infants, no significant gradient was observed in the right pulmonary artery. We conclude that, at least in the preterm infant, transient peripheral pulmonary stenosis is not present at birth but is an acquired phenomenon closely related to closure of the ductus arteriosus.

Blood Flow Velocity↗
PubMed1991

[Cardiac insufficiency in children. Mechanisms and treatment].

The treatment of cardiac failure has been improved in recent years by a better knowledge of the factors that regulate the performance of the heart. In particular, we can manipulate the loading conditions of the heart, independent of, or in association with efforts to directly stimulate the contractility of the myocardium. We discuss new approaches of the treatment, especially with regard to the mechanisms of congestive heart failure.

Cardiotonic Agents↗
PubMed1990

Effect of intermittent positive pressure ventilation on diastolic ventricular filling patterns in premature infants.

Eleven preterm newborn infants had a Doppler echocardiographic examination of their ventricular filling patterns during intermittent positive pressure ventilation. Peak velocity during early ventricular filling (VE) and during atrial systole (VA) and diastolic velocity-time integral of early (IE) and late (IA) ventricular filling caused by atrial contraction were measured. The ratios of VE/VA and IE/IA were also calculated. Diastolic peak velocities, as well as the diastolic velocity-time integral of early and late ventricular filling measured through the mitral valve were significantly higher during inspiration. The peak of the wave representing the velocity during atrial systole (A) was always higher than the peak of the wave representing the velocity of early ventricular filling (E). As a result, the ratio of these two variables (E/A) was always less than 1, showing no significant variation from inspiration to expiration. The flow patterns into the right ventricle were the opposite of those observed through the mitral valve. During inspiration, a significant decrease (p less than 0.001) in peak and time integral velocities of both the early ventricular filling and atrial systole waves was observed. Heart rate did not vary with respiration. It is concluded that during positive pressure ventilation, inspiration decreases right ventricular filling and enhances left ventricular filling. Opposite changes are recorded during expiration. Early and late phases of diastolic filling are equally affected. These changes are different from those observed during spontaneous breathing and should be taken into account in the assessment of diastolic ventricular function in preterm infants requiring assisted ventilation.

Blood Flow Velocity↗
PubMed1988

Increased oxygen affinity with normal heterotropic effects in hemoglobin Loire [alpha 88(F9)Ala----Ser].

Increased homotropic allosteric effect, while maintaining normal heterotropic effects, was observed in hemoglobin Loire. The oxygen binding curves, at equilibrium, and the kinetic measurements demonstrated that the substitution of alpha 88(F9) Ala for a Ser results in increased oxygen affinity and decreased n50 value. The function of the residues involved in the Bohr effect or in the regulation by 2,3-bisphosphoglycerate is not altered. The effects of bezafibrate, which binds specifically to the alpha chains, was similar to that observed in Hb A. The functional properties of Hb Loire may be explained by a slight displacement of some key residues of the C-terminal region of the alpha chain destabilizing the T structure.

2,3-Diphosphoglycerate↗