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P Arbeille

Publications and source records attributed to P Arbeille.

At least 19 recordsLinked to original sources
PubMed1992

New implanted Doppler sensors for the assessment of the main fetal hemodynamics.

If the fetal Doppler examination during human pregnancies provides useful information to the obstetrician, it does not allow us to collect all the biological and haemodynamic data required to understand the physiopathological mechanisms involved in the development of intrauterine growth retardation (IUGR) and hypoxia. With the animal model, it is possible to have access to the blood pressure, the blood velocity and volume, to collect blood sampling and to perform pharmacological tests, or to simulate some human pathology. Several studies have been already carried out on lamb fetuses using electromagnetic flowmeters placed around the cord and catheters, with pressure sensors placed inside the fetal aorta. Most of the time only the umbilical flow was assessed on the fetal side. The aim of the present work was to develop a new Doppler system able to monitor in real time and simultaneously, the fetal cerebral and the umbilical arterial flows as well as the uterine circulation. New flat Doppler probes have been designed, to be implanted on the fetus and on the mother, which makes possible the atraumatic assessment of fetal and maternal flows during approximately 20 days. The 4-MHz CW Doppler probe consists of two rectangular piezoelectric transducers of 13-mm wide, preoriented at 45 degrees from the surface of the probe, placed in a 6-mm-high plastic case in which small holes are made to sew the probe on the fetal skin. The sensors are fixed on the fetal skin, facing the umbilical cord, the fetal cerebral arteries and in front of the uterine arteries.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1992

Nicotine-induced changes in the cerebral circulation in ovine fetuses.

Pulsed Doppler ultrasound was used to investigate fetal and maternal ovine circulation in 16 ewes. Resistance index (R) was measured at the following sites: umbilical, fetal cerebral, and uterine arteries. Measurements were performed at days 80, 100, and 130 of gestation, day 0 being the day of mating. Normal ranges of the Doppler indices were delimited on the six control ewes. Five ewes were treated by intramuscular injection of 10 mg of nicotine 5 days per week and five others received placebo injections. No difference was found on the Doppler indices between the control group and the placebo group. The cerebral indices did not differ in the three groups at days 80 and 100 but were significantly higher at day 130 in the nicotine group in comparison to the two others (p less than 0.01). The umbilical indices were slightly elevated at days 80 and 130 in the nicotine group. No significant difference was found on the uterine indices at any of the three stages of gestation whatever the treatment. In the control and placebo groups the ewes delivered in the normal ranges of gestation length. In these groups 2 of 20 lambs (10%) died at birth. In the nicotine group 2 ewes delivered prematurely and 8 of the 13 lambs (62%) were stillborn. In conclusion, repeated nicotine injections induce vasoconstriction on the umbilical and cerebral arteries of the fetus at the end of the gestation and are associated with poor perinatal outcome.

Animals↗
PubMed1992

Hemodynamic and hormonal effects of prolonged anti-G suit inflation in humans.

This study examined the hemodynamic consequences of prolonged lower body positive-pressure application and their relationship to changes in the plasma concentration of the major vasoactive hormones. Six men [36 +/- 2 (SE) yr] underwent 30 min of sitting and then 3 h of 70 degrees head-up tilt. An antigravity suit was applied (60 Torr legs, 30 Torr abdomen) during the last 2 h of tilt. In a similar noninflation experiment, the endocrine responses were measured in the suited subjects tilted for 3 h. Two-dimensional echocardiography was used to calculate ventricular volume and cardiac output. Measurements were made 30 min before and 30 and 90 min after inflation. Immediately after inflation, mean arterial pressure increased by 7 +/- 2 Torr and heart rate decreased by 16 +/- 4 beats/min. Left ventricular end-diastolic volume and systolic volume increased significantly (P less than 0.05) at 30 and 90 min of inflation. Cardiac output increased after 30 min of inflation and returned to the preinflation level at 90 min. Plasma norepinephrine and plasma renin activity were maximally suppressed after 15 and 90 min of inflation, respectively (P less than 0.05). No such hormonal changes occurred during control. Plasma sodium, potassium, and osmolality remained unchanged during both experiments. Thus, prolonged application of lower body positive pressure induces 1) a transient increase in cardiac output and 2) a marked and sustained decrease in plasma norepinephrine and plasma renin activity, which reflect an inflation-induced decrease in sympathetic activity.

Adult↗
PubMed1992

Hemodynamic foundation of umbilical arterial Doppler waveform analysis.

This paper reviews various in vitro and in vivo studies which have been conducted to investigate the influence of central and peripheral circulatory factors on the Doppler indices. These studies indicate that the Doppler indices are affected by both central and peripheral hemodynamics. Of the central factors, the heart rate influences the indices predominantly through the variations during the diastolic phase of the cardiac cycle. This was confirmatory of the clinical findings. Of the other central factors, cardiac contractility may not affect the rising slope of the Doppler waveform. Regarding the peripheral hemodynamics, both in vitro and in vivo studies confirm that the indices reflect the changes in the peripheral resistance; however, opposition to flow in a pulsatile flow can be adequately described only by impedance. Initial in vivo and in vitro studies demonstrate that the indices correlate well with the impedance parameters. However, this is true only when the central circulation remains stable.

Animals↗
PubMed1992

Head-down tilt bedrest. HDT'88--an international collaborative effort in integrated systems physiology.

An international collaborative project, initiated by the DLR-NASA Life Sciences Working Group, led to the performance of a head-down tilt bedrest (HDT) study at the DLR Institute for Aerospace Medicine. Scientific and operational questions were addressed in preparation for the D-2 Spacelab mission. Principal areas of interest were cardiovascular regulation and fluid/electrolyte metabolism. The results are detailed in a series of 13 reports to which the present paper serves as an introduction.

Adaptation, Physiological↗
PubMed1992

Cardiovascular response to lower body negative pressure before, during, and after ten days head-down tilt bedrest.

The haemodynamic response to lower body negative pressure (LBNP) was studied in 6 test subjects before (baseline), during, and after (recovery) ten days of 6 degrees head-down bedrest. The LBNP protocol consisted of a 35 min control period, application of a staircase differential pressure profile (15 min at -15 mmHg; 5 min at -30 mmHg; 15 min at -40 mmHg), and a 10 min post-stress observation period. Cardiac output was measured by a foreign gas rebreathing technique. Finger plethysmographic arterial blood pressure (BP), ECG, and heart rate (HR), lower limb crossectional area, and the electrical impedance of three body segments were recorded continuously. As expected, HDT caused a decrease in plasma volume and total body fluid volume. Resting CO at the end of HDT was 16% below the baseline level and similar to CO in the upright position before HDT. Stroke volume (SV) was also reduced, but there were no significant changes in control HR or BP. Absolute changes in CO and SV during LBNP were similar at baseline and during HDT, but the relative changes were larger during HDT. HR and vasoconstriction responses were enhanced, but presyncope occurred in two subjects. Reduced cardiac filling with decreased stroke volume at rest is the apparent primary cause of the altered LBNP response during HDT.

Adult↗
PubMed1992

Results of a 4-week head-down tilt with and without LBNP countermeasure: I. Volume regulating hormones.

The volume regulating hormones were studied during a 4-week head-down tilt (CNES HDT) in five subjects with and without (controls) lower body negative pressure (LBNP). LBNP was applied 3 times a day for 3 weeks, 4 times a day for 4 d, and 6 times a day for 3 d the last week. In both groups we observed a significant decrease in body weight (3% in controls, 0.8% in LBNP), a significant increase in plasma renin activity and aldosterone (with an amplification of their rhythms), and a significant decrease in norepinephrine with no difference between the two groups. The only major hormonal difference was observed for atrial natriuretic factor (ANF), which decreased significantly in the control group and increased in the LBNP group. These results are compared with the improvement in orthostatic tolerance (OT) after HDT in the LBNP group in the same protocol (17). We conclude that many factors could be involved in the improvement of OT. The results suggest that better conservation of plasma volume in the LBNP group might have prevented a decrease in ANF. Whether ANF plays a role in the regulation of baroreceptor reflex with an improvement in OT is currently unknown.

Aldosterone↗
PubMed1992

Results of a 4-week head-down tilt with and without LBNP countermeasure: II. Cardiac and peripheral hemodynamics--comparison with a 25-day spaceflight.

Cardiovascular hemodynamics were assessed by ultrasound echography and Doppler during a 28-d head-down tilt "CNES HDT: 87-88," and during the 25-d French-Soviet spaceflight "Aragatz 88." For both studies we used the same ultrasound methodology. The main hemodynamic parameters of the left heart function and of the peripheral arterial system (cerebral, renal, femoral arteries) were measured four times during the HDT (day 7, 14, 21, 28) and twice post-HDT. The same measurements were performed six times during the flight (day 4, 5, 15, 18, 20, 24) and five times postflight. During the HDT, two groups were studied: six subjects no countermeasures and six subjects with repeated lower body negative pressure (LBNP). In the first group the cardiac volumes and the cardiac output were significantly decreased, whereas in the group with LBNP these parameters were superior to the basal value. In the group without LBNP the cerebral flow was maintained because of a decrease of the brain vascular resistance. In this group the renal vascular resistance was decreased as inflight. In the lower limbs we observed a loss of the vasomotor control. The vascular resistance was decreased after the end of the HDT and the subjects suffered orthostatic intolerance. In the population with LBNP, we did not observe the same decrease of vascular resistance during the HDT, and after the HDT no sign of orthostatic intolerance was observed. During the flight, the left ventricular volume was significantly decreased. The carotid flow was maintained owing to a decrease of the cerebral vascular resistance.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1991

[Evaluation of cerebral hemodynamics by transcranial Doppler in anesthesia and reanimation].

Doppler technics are widely used for the investigation of the peripheral flows. The main objective of the method is to detect and quantify the vascular disease (stenosis, arterio-venous malformation) at the level of the carotid bifurcation or on the intracranial vessels. The spectral analysis provides informations on the velocity profile, and allows to quantify systolic, diastolic, and mean frequencies from which the usual haemodynamic parameters are determined. In case of vasospasm, the maximal frequency increases significantly (> 3 kHz). The amplitude of the diastolic flow is related to the vascular resistance. Vascular disease or distal vessel compression make the resistance increase; on the contrary vasodilation decreases the vascular resistance. The Doppler index R = S-D/S, with S and D the systolic and diastolic amplitude is generally accepted to change in proportion with the vascular resistance. The blood flow volume can be evaluated from the mean Doppler frequency, the vessel diameter, and the angle theta between the vessel and the Doppler beam. In case of intracranial arteries the diameter cannot be accurately measured by echography. Nevertheless if the diameter does not change and the angle theta remains constant, the variations of the mean frequency represent the blood flow volume changes. If there is a vasospasm, this method cannot be used, and the only possibility to evaluate the cerebral blood flow changes is to measure the variations of the common carotid blood flow or carotid mean frequency. The haemodynamic parameters are used in anesthesiology or in intensive care.(ABSTRACT TRUNCATED AT 250 WORDS)

Anesthesia, General↗
PubMed1990

[The contribution of color-coded Doppler in early vascular complications of kidney transplantation].

Ultrasound techniques and radionuclide studies are very often used to assess vascularization of renal transplants. Although, in acute tubular necrosis or acute rejection, it is difficult to choose between these two techniques, in 3 recent cases of renal artery thrombosis, we conclude that color coded Doppler is preferable to nuclear medicine or duplex system to diagnose this form of thrombosis.

Adult↗
PubMed1989

Doppler assessment of the intracerebral circulation of the fetus.

Fetal cerebral arteries have been explored during normal pregnancies (n = 40). The index of cerebral resistance (Rc) as defined by Pourcelot (Rc = (S-D)/S where S is the systolic amplitude and D is the diastolic amplitude) shows variations similar to the placental index (Rp). During normal pregnancy, the cerebral index is higher than the placental index and the cerebro-placental ratio (Rc/Rp) is greater than one. This preliminary study of the umbilical and cerebral circulation during 21 pathological pregnancies with hypertension seems to demonstrate that when fetal growth retardation is also present (n = 6) either or both of the indices Rc and Rp may be outside the normal range but the cerebro-placental ratio (CPR) is always less than one. However, a larger number of patients needs to be explored in order to evaluate the clinical usefulness of such an observation.

Adult↗