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Biomedical subjects

M Berson

Publications and source records attributed to M Berson.

At least 19 recordsLinked to original sources
PubMed1995

Vascular resistance quantification in high flow resistance areas using the Doppler method.

The objective of the present study is to define and validate on an animal model (ewe) a new Doppler parameter for the assessment and monitoring of the vascular resistances in high resistance to flow areas (lower limbs, placenta with vascular disease). The high resistance index (HRI) was derived from the transmission line theory and defined as: HRI = D/S with S the amplitude of the systolic peak and D that of the diastolic reverse flow. Validation of the HRI was performed on adult ewes. Distal lower limb vascular resistances were evaluated from the Doppler femoral waveform (HRI) and compared with the classic vascular resistances (Rv), calculated from pressure and flow (mmHg/mL/min). The femoral flow variations were measured by duplex (echo-Doppler) method and the mean pressure through an arterial catheter inserted into the abdominal aorta. Two tests were used in this study: (1) A calibrated venous compression of the lower limbs extremity: The femoral flow dropped by 29%, the pressure and heart rate did not change, the HRI increased by 37% (p < 0.01), and the vascular resistance (Rv) by 46% (p < 0.01). (2) The intravenous injection of 1 mg adrenaline: The arterial pressure increased by 70% (p < 0.001), the heart rate and femoral flow dropped by 50% (p < 0.001), and 35% (p < 0.001), the HRI increased by 70% (p < 0.01) and the vascular resistances (Rv) by 140% (p < 0.01). During the two tests, the HRI changed in proportion with the "classic" vascular resistances.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1995

Assessment of the fetal PO2 changes by cerebral and umbilical Doppler on lamb fetuses during acute hypoxia.

The objective of the present study was to validate one or a combination of fetal Doppler parameters in order to assess acute fetal hypoxia in an ovine model. Acute hypoxia was induced by reducing umbilical, or maternal aortic flow (approx. 70%). A CW Doppler probe was fixed on the fetal cervical skin, facing the internal carotid artery and the fetal abdominal skin adjacent to the umbilical arteries. (The angle between Doppler beam and flow vector remained constant.) A "Doptek 3000" spectrum analyser was used to measure the maximal and mean Doppler frequencies. Heart rate (HR), umbilical blood flow (UBF), carotid blood flow (CBF), umbilical RI (URI), cerebral RI (CRI) and cerebroplacental ratio (CPR = CRI/URI) were calculated in real time. A catheter was inserted into the fetal femoral artery, for blood gas (PO2, PCO2 pH) and blood pressure (BP) measurements. After 1 min of aorta compression (70% aortic flow reduction), the URI increased by 10% (P < 0.05), and the UBF decreased by 10% (P < 0.05), but the CRI decreased by 20% (P < 0.02), and the CBF did not change significantly. Fetal PO2 and CPR fell down after 1 min (59% and 38%, respectively; P < 0.001), although strong fetal heart rate decelerations were observed. The blood pressure, PCO2 and pH did not change significantly during this test. Throughout the 12 min of cord compression (70% umbilical flow reduction) the URI increased (70% to 80% P < 0.001), and the UBF decreased (approx. 60%; P < 0.001), but the CRI decreased (approx. 25%; P < 0.01), and the CBF remained constant (+/- 5%; ns). Fetal PO2 and CPR all decreased during the compression (30% to 44% and 40% to 60%, respectively; P < 0.001). HR, pH and PCO2 did not change significantly. During cord compression the blood pressure did not change significantly. In both cases, the CPR decreased significantly (P < 0.001) with the PO2 in the same direction and with a comparable amplitude (-30% to -50%). Nevertheless, the drop in CPR was greater during cord compression than during aorta compression, probably because the compression of the cord induced a central hypovolemia in addition to the hypoxia. The CPR was found to be the hemodynamic parameter that followed most closely the PO2 acute changes. The amplitude of the variations of this parameter (-30% to -50%) were quite similar to those of the PO2 during the period of acute hypoxia.(ABSTRACT TRUNCATED AT 400 WORDS)

Acute Disease↗
PubMed1995

[Quantification and monitoring of vascular resistance in the lower limbs by the Doppler method (animal model)].

The object of this study was to define and validate a non-invasive method of evaluation and monitoring of vascular resistances in the leg. Blood flow velocity was measured by Doppler ultrasound in an animal model (ewe) with similar blood flow characteristics in the lower limb as man and allowing access to the required invasive measurements for validation of the method (pressure and flow). Vascular resistances distal to the measuring point (femoral, for example) were assessed using the resistance index R = D/S, S being the peak systolic deflection and D that of diastolic reflux of the Doppler spectral analysis of flow in the femoral artery. The values and variations of this resistance index were compared with the vascular resistances calculated from measurements of pressure and flow at the point of Doppler sampling and expressed in mmHg/ml/min. Femoral flow was measured by Doppler ultrasound (Doppler-echo), and mean pressure by an arterial catheter introduced into the abdominal aorta. Compression of the lower limb veins induced a venous return resulting in a reduction of cardiac output and femoral flow. During compression, femoral flow decreased by an average of 29% (p < 0.001) although mean pressure and heart rate did not change significantly. The femoral resistance index (Rf) increased by an average of 37.5% (p < 0.01) and vascular resistances increased by 45.9% (p < 0.01). Injection of 1 mg adrenaline induced peripheral vasoconstriction with an increase in blood pressure and a decrease in heart rate and femoral flow.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1994

Concurrent changes in intracranial pressure, cerebral blood flow velocity, and brain energy metabolism in rabbits with acute intracranial hypertension.

The relationship between intracranial pressure or cerebral perfusion pressure (CPP), cerebral blood flow, and brain energy failure is unpredictable throughout the development of acute intracranial hypertension. The purpose of the present study was to correlate intracranial pressure with cerebral blood flow velocities and brain energy metabolism in adult rabbits. The acute intracranial hypertension was achieved by pressure transmission. Transcranial Doppler wave-forms were obtained from the basilar artery for monitoring cerebral blood flow velocities. 31P-Magnetic resonance spectroscopy was used to assess brain energy metabolism. The diastolic blood flow velocity began to decrease significantly (34.5%) when the intracranial pressure was equal to half the diastolic arterial pressure for a CPP of 36 +/- 18 mmHg. Circulatory cerebral resistances increased significantly (55%) for the same value of CPP. Diastolic frequency was near zero when intracranial pressure approached diastolic arterial pressure (51 +/- 12 mmHg), corresponding to a CPP of 30 +/- 15 mmHg. At the same time, only a tendency for brain energy metabolism to decrease was observed. Consequently, transcranial Doppler sonography could be proposed for the follow-up of intracranial hypertension. Magnetic resonance spectroscopy could help to monitor these patients and could be especially proposed in case of high intracranial pressure (near diastolic arterial pressure). The joint use of these two methods would help in making appropriate therapeutic decision in humans.

Animals↗
PubMed1994

Study of cutaneous extensibility in lymphoedema of the lower limbs.

We have studied changes in the elasticity and viscosity of the skin in patients with lymphoedema, using a technique involving vertical extensibility by suction. We measured parameters which included immediate extensibility (Ue, which reflects the elastic properties of the skin), and delayed extensibility (Uv which reflects intracutaneous movements of a viscous type). In grade III lymphoedema, Ue is decreased and Uv is increased. These changes are explained by volume variations and histological alterations, and tend to normalize after treatment. Our study shows that measurement of extensibility is useful in evaluation of volume variations, effects of therapy, and disease evolution, as Ue variations correlate with volume variations and with Uv changes. This technique also provides information which is useful in assessing patients' functional difficulties in relation to skin infiltration, and might be of value in lymphoedema follow-up.

Adolescent↗
PubMed1994

Ultrasound imaging of psoriatic skin: a noninvasive technique to evaluate treatment of psoriasis.

BACKGROUND: The aim of our study was to image psoriasis plaques by ultrasound to assess the changes in psoriasis and to measure and quantify them objectively. MATERIALS AND METHODS: Thirty-one psoriasis plaques were studied in 19 patients. Measurements of skin thickness were obtained with a high resolution B-mode echographic system. RESULTS: Some changes were seen in psoriatic skin. A new structural element was observed: a wide subepidermal nonechogenic band. The other changes were a decrease in dermal echoes that were less intense and less dense, and an increase in the epidermal and dermal skin thicknesses. The skin thickness was increased in all psoriasis plaques as compared to apparently normal skin (P < 0.001). The average increase was 67% for whole skin and 200% for epidermis. CONCLUSIONS: Ultrasound imaging of psoriatic skin allowed the identification of different skin changes induced by psoriasis, and particularly, the differentiation between epidermal and dermal alterations. We presume that epidermal thickness reflects epidermal proliferation and desquamation, and the increase in the dermal and whole skin thickness reflects infiltration. We feel that ultrasound imaging of psoriatic skin is a quantitative method that is as easy and noninvasive as the psoriasis area and severity index (PASI). It could be used for following up patients with psoriasis and could achieve widespread use, especially in research protocols.

Adult↗
PubMed1994

Cerebral vasodilation capacity: acute intracranial hypertension and supra- and infra-tentorial artery velocity recording.

This experiment is the first to compare cerebral vasomotor reactivity in the supra- and infra-tentorial regions in baseline conditions and during progressive acute intracranial hypertension. The increase in intracranial pressure was performed using liquid pressure transmission in two groups of 16 rabbits by elevating a saline infusion bottle connected to the subdural space. Cerebral microvessel dilation capacity was studied using acetazolamide arterial infusion during three stages of 20 min: at baseline conditions, with an intracranial pressure value equal to half the diastolic arterial pressure and with an intracranial pressure equal to the diastolic arterial pressure. The effects of acetazolamide in the basilar artery and in the carotid siphon were simultaneously monitored by transcranial Doppler sonography during all the experiments. The changes in cerebral vasomotor reactivity occurred with the same intensity and latency in both vascular compartments in baseline conditions. The maximum amplitude of changes happened 30 s later in the basilar artery than in the carotid siphon. When intracranial pressure was above half the diastolic arterial pressure, the vasomotor tone began to decrease in the carotid siphon which supplies a small region of the rabbit brain, whereas it was maintained in the basilar artery. This effect could be explained by brain tissue hypertension. Vasomotor reactivity had nearly disappeared in all the cerebral arteries investigated when intracranial hypertension was equal to the diastolic arterial pressure. These results show evidence of a direct and late effect of acute elevation of intracranial pressure on cerebral microvascular tone. This begins in the supra-tentorial region but there is an early local effect on the carotid siphon due to the brain tissue pressure.

Animals↗
PubMed1993

Detection of fetal breathing and cardiac movements and rhythms in ultrasonic Doppler signal recorded on the surface of the maternal abdomen.

It is proposed to use information on the direction of reflector movement and extensive filtering in the detection of fetal breathing and cardiac movements in the ultrasonic Doppler signal recorded on the surface of the material abdomen. The method appears fairly insensitive to spurious signals and allows those of interest to be distinguished without any reference technique. A decision rule for breathing and cardiac rhythm detection, incorporating movement direction, amplitude, shape and periodicity criteria, is also proposed.

Female↗
PubMed1993

[Refinement of a new Doppler sensor for studying fetal hemodynamic disorders (animal model)].

Fetal Doppler techniques applied in the human have furnished information of the regional haemodynamics of fetal circulation but has in general been associated with haemodynamic data obtained by vessel puncture, i.e. arterial pressure or blood gases. With animal models, further data can be obtained in the course of induced pathologies or during dynamic test (hypoxia, drugs). Several studies on utero-placental haemodynamics have been conducted using electromagnetic sensors and implanted catheters. This type of technique is only possible for certain vessels (usually the cord vessels) and, for example, cannot be used to investigate the cerebral area. The aim of this work was to develop a Doppler sensor which could be implanted in utero on the fetus and would permit a real time measurement of the major fetal blood flows. The sensor was made of 2 continuous Doppler transducers (13 mm x 4 mm) with a 45 degrees inclinasion to the sensor surface and carried on a parallellopipedic support system measuring 20 mm x 6 mm. The active surface of the transducer has a silicone film covering. The sensor is placed on the skin of the fetus, facing the artery to be explored, and oriented towards capture of a quality signal. The sensor is then sutured to the skin and the coaxial leads of the 2 transducers are exposed through the skin of a pregnant ewe. The leads are connected to a Doppler control panel later after the operative period. Three sensors can be implanted simultaneously to monitor umbilical, cerebral and uterine blood flows.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
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

High-resolution real-time ultrasonic scanner.

High spatial resolution is required for echographic exploration of the skin, microvessels or small laboratory animals. With the scanner described here, high resolution is obtained by means of a strongly focused, wide-band 17 MHz center frequency transducer (-6 dB bandwidth: 22 MHz). The movement of this transducer above the skin provides a 6 mm wide and 5 mm deep echographic cross-section with an image rate of 15 images/s. The resolution is about 0.08 mm in axial and 0.2 to 0.3 mm in lateral directions. The device was tested on phantoms in water and in vivo on normal and pathological skin in the Department of Dermatology. With the easy-to-handle probe, explorations were made on psoriasis, basocellular carcinoma, malignant melanoma and sarcoidosis.

Basal Cell Carcinoma↗
PubMed1992

Acute intracranial hypertension and basilar artery blood flow velocity recorded by transcranial Doppler sonography: an experimental study in rabbits.

The relationship between intracranial hypertension and basilar artery blood flow is not well known, and it is not yet definite that the reduction of cerebral flow depends on cerebral perfusion pressure rather than microvessel compression. The purpose of the study described here was to investigate the effect of acute intracranial pressure on the basilar flow velocity, the cerebral perfusion pressure, and the systemic arterial pressure. The basilar Doppler signal was recorded continuously in 24 New Zealand rabbits by transcranial pulsed Doppler method. The acute intracranial hypertension was induced by the progressive raising, in steps of 5 mmHg, of a saline infusion bottle connected to an epidural sensor. The intracranial hypertension induced a decrease in diastolic and mean flow velocities in the basilar artery, and an increase in the resistance index. Cerebral perfusion pressure was significantly correlated with flow parameters. The basilar diastolic flow began to decrease significantly from a 35-40 mmHg intracranial pressure and for a 37 mmHg + 20 SD cerebral perfusion pressure, without significant variation of arterial pressure. Diastolic flow dropped to zero for a 53 mmHg intracranial pressure and a 30 mmHg + 15 SD cerebral perfusion pressure. These results show that high intracranial pressure values are necessary for significantly reducing basilar artery blood flow. This effect, and the increase of circulatory cerebral resistance, occurred before significant changes in systemic arterial pressure.

Animals↗
PubMed1991

Evaluation of cerebral blood flow in rabbits with transcranial Doppler sonography: first results.

A transcranial Doppler sonographic system with a special 2-MHz probe for prolonged experimentation has been developed for Doppler waveform recordings from the basilar artery on rabbits. Measurements were made from the maximum velocity wave form, and Pourcelot's resistance index was used to express the results. The diastolic flow, similar to that observed in humans in physiological conditions, decreases with increased intracranial pressure during chronic intracranial hypertension. This Doppler model may be valuable for assessing rapid changes of cerebral blood flow in conscious animals during prolonged or acute experimental procedures.

Animals↗
PubMed1989

Visualization of the fetal circle of Willis and intra-cerebral arteries by color-coded Doppler.

We report here the visualization of the intra-cerebral vessels in a normal fetus of 28 weeks gestational age, by color-coded Doppler. The color-flow mapping method makes it possible to identify very small vessels that up to date could not be detected on B-mode imaging, and will permit new clinical and physiological studies of the circulation in specific areas of the fetal brain.

Cerebral Arteries↗
PubMed1989

Very high frequency pulsed Doppler apparatus.

A study of a method for exploration of microvessels is presented. Theoretical considerations taking into account the backscattering of ultrasound wave from a red cell and the attenuation versus frequency (up to 180 MHz) show that a frequency in the range of 80 to 120 MHz is most favorable for small depths of exploration (300 microns). The characteristics of the 113 MHz Doppler system which was built are described. The minimum detectable signal is 3 microV, the lateral resolution around 20 microns and the minimum length of the Doppler sample volume about 80 microns. The Doppler data are displayed in the form of a frequency spectrum. The first encouraging tests carried out using 20 microns rectangular glass capillary tubes and 50 to 150 microns microvessels of the mesentery of rat have demonstrated the resolution and the sensitivity of the system. A discussion illustrates the difficult problem of motion artefacts and the improvements which have to be made. From a technical point of view the authors think that it is possible to work with such a high frequency but there are two main difficulties: the processing of a very low frequency Doppler spectrum and the optimization of the probe (dimensions and shape).

Animals↗
PubMed1988

Fetal cerebral circulation assessment by Doppler ultrasound in normal and pathological pregnancies.

During normal pregnancies (n = 40) the cerebral index (Rc = S - D/S) (with S = systolic and D-telediastolic amplitudes) is always higher than the placental index (Rp), and the cerebro/placental ratio (Rc/Rp) greater than 1. Of 29 pregnant women with hypertension (including two twins), 17 delivered normally (Rc, Rp and CPR normal), 14 delivered an hypotrophic fetus, in 12 out of these 14 pregnancies one of the two indices (Rc or Rp) was abnormal and the cerebro/placental ratio, CPR, was always less or equal to 1. CPR sensitivity was 86% the specificity 100%. In 11 pregnancies with idiopathic fetal-growth retardation, the CPR was less or equal to 1 in eight cases (73% of the cases), and greater than 1 in three cases (three false-negative results).

Cerebrovascular Circulation↗