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Biomedical subjects

M Dauzat

Publications and source records attributed to M Dauzat.

At least 19 recordsLinked to original sources
PubMed1998

Short- and medium-term duplex sonography follow-up of deep venous thrombosis of the lower limbs.

PURPOSE: We conducted this study to assess the progression or regression of venous thrombi during and after treatment and to search for criteria of embolism risk. METHODS: We prospectively studied 75 patients with lower limb deep venous thrombosis. We used B-mode sonography for the diagnosis and follow-up of these thrombi. Pulmonary scintigraphy was performed at days 1 and 10. We evaluated the topography, echogenicity, and structure of the thrombus; the location and wall attachment of its head; and the vein diameter. Each venous segment was semiquantitatively scored as follows: 0, no thrombosis; 1, partially obstructive thrombosis; or 2, complete thrombosis. RESULTS: The decreases in the total thrombosis score were 4%, 11%, 51%, 72%, and 84% on days 5, 10, 30, 90, and 365 (1 year), respectively. Pulmonary embolism occurred in 27 patients, of whom 16 were asymptomatic. Thrombi in iliac veins exhibited a slower regression rate than those in calf and femoral veins. Pulmonary embolism occurred in 54% of patients with versus 24% of patients without a floating thrombus head. CONCLUSIONS: Sonography is useful for the early detection of thrombus progression and the evaluation of embolism risk, which seems to be greater in patients with a floating thrombus head.

Disease Progression↗
PubMed1998

Doppler study of mesenteric, hepatic, and portal circulation in alcoholic cirrhosis: relationship between quantitative Doppler measurements and the severity of portal hypertension and hepatic failure.

To determine the relationship between quantitative Doppler parameters of portal, hepatic, and splanchnic circulation and hepatic venous pressure gradient (HVPG), variceal size, and Child-Pugh class in patients with alcoholic cirrhosis, we studied forty patients with proved alcoholic cirrhosis who underwent Doppler ultrasonography, hepatic vein catheterization, and esophagoscopy. The following Doppler parameters were recorded: time-averaged mean blood velocity, volume flow of the main portal vein flow, and resistance index (RI) of the hepatic and of the superior mesenteric artery. Doppler findings were compared with HVPG, presence and size of esophageal varices, and Child-Pugh class. There was a significant inverse correlation between portal velocity and HVPG (r = -.69), as well as between portal vein flow and HVPG (r = -.58). No correlation was found between RI in the hepatic artery or superior mesenteric artery and HVPG. No correlation was found between portal vein measurements and presence and size of varices. Severe liver failure was associated with lower portal velocity and flow. In patients with alcoholic cirrhosis, only portal vein blood velocity and flow, but neither hepatic nor mesenteric artery RI, are correlated to the severity of portal hypertension and to the severity of liver failure.

Adult↗
PubMed1998

Training is required to improve the reliability of esophageal Doppler to measure cardiac output in critically ill patients.

OBJECTIVES: Assessment of and effect of training on reliability of esophageal Doppler (ED) versus thermodilution (TD) for cardiac output (CO) measurement. DESIGN: Prospective study. SETTING: Intensive care unit of a university hospital. PATIENTS: 64 consecutive critically ill patients requiring a pulmonary artery catheter, sedation, and mechanical ventilation. INTERVENTIONS: Esophageal Doppler CO measurements were performed by the same operator, whereas TD CO measurements were carried out by other independent operators. A training period involving the first 12 patients made the operator self-confident. In the remaining patients, the reliability of ED was assessed (evaluation period), using correlation coefficients and the Bland and Altman diagram. Between training and evaluation periods, correlation coefficients, biases, and limits of agreement were compared. MEASUREMENTS AND RESULTS: During training and evaluation periods, 107 and 320 CO measurements were performed in 11 out of 12 patients and in 49 out of 52 patients, respectively. Continuous CO monitoring was achieved in 6 out of 11 patients and in 38 out of 49 patients during training and evaluation periods, respectively. Between the two periods, correlation coefficients increased from 0.53 to 0.89 (p < 0.001), bias decreased from 1.2 to 0.1 l x min(-1) (p < 0.001), and limits of agreement decreased from 3.2 to 2.2 l x min(-1) (p < 0.001). CONCLUSION: A period of training involving no more than 12 patients is probably required to ensure reliability of CO measurement by ED.

Aged↗
PubMed1998

Can cerebrovascular microemboli induce cognitive impairment in patients with prosthetic heart valves?

Doppler ultrasonography can be used to detect the presence of emboli in the cerebral arterial circulation. Emboli can be produced by different sources and can be of different nature: solid elements as thrombi, platelet aggregates or atheromatous material, or gaseous when they are produced during the decompression phase of diving or during extracorporeal circulation (ECC) procedures. A more recent source of emboli has been found in the mechanical prostheic heart valves (MHV). The emboli generated by MHV are likely of gaseous nature and are found in the middle cerebral artery blood flow at a variable rate, where they are detected by transcranial Doppler sonography. The mechanism of production of these microbubbles may be related to the rapid leaflet motion especially at closure when very high local pressure gradients appear, which may be able to provoke a release of the disolved blood gas. Solid element emboli constitute a major cause of cerebrovascular disease and particularly stroke. Conversely, gaseous emboli coming from ECC or MHV are considered as clinically silent. Nevertheless, cognitive alterations have been reported after ECC. As the MHV carriers are chronically submitted to embolic events, it can be assumed that cognitive impairments may occur also in these patients. A preliminary study was designed to inpatients attention and memory in patients with normally functioning MHV and microemboli, with biological prosthesis and in normal subjects. In the two groups of patients, episodic memory was significantly altered relatively to the control group. In the MHV carriers group, a significant decrease in working memory performance was observed relatively to the two other groups. These results confirm a long term effect of the microembolization occuring during ECC and point out the effect of the chronic exposition to microemboli.

Bioprosthesis↗
PubMed1998

Pulsed Doppler ultrasonography guidance for catheterization of the subclavian vein: a randomized study.

BACKGROUND: Catheterization of the subclavian vein may lead to severe complications. The current randomized study compared a technique of pulsed Doppler ultrasonography guidance and the standard method for subclavian vein catheterization. METHODS: Standard and Doppler ultrasonography guidance methods were performed by the same physician in 286 patients, 143 in each group. Primary end points were immediate complications (arterial puncture, pneumothorax, wrong position of catheter tip), failures, the number of subclavian vein catheterizations with immediate complication or failure, the number of skin punctures per catheterization, and the time to placement of the guide wire. The secondary end points were the determination of predicting factors of successful cannulation in each group. RESULTS: Both groups were similar according to morphologic parameters of the patients. A greater number of subclavian vein catheterizations were performed on the right side using Doppler guidance (105 vs. 73, P < 0.01). Doppler guidance decreased complications (5.6% vs. 16.8%, P < 0.01), largely because of a smaller number of catheters for which the tip was defined to be in incorrect position (0.7% vs. 7.7%, P < 0.01). The time to catheterization was longer with Doppler guidance (300 vs. 27 s, P < 0.001). Failures, catheterizations of the subclavian vein with immediate complications or failure, and the total number of skin punctures per catheterization were similar in both groups. Using Doppler guidance, the presence of a good Doppler signal (124 of 143) was predictive of successful catheterization (123 successful cannulations, P < 0.001). CONCLUSIONS: Doppler guidance reduces the incidence of inappropriately positioned subclavian catheters.

Adult↗
PubMed1997

Diagnosis of acute lower limb deep venous thrombosis with ultrasound: trends and controversies.

Acute deep venous thrombosis of the lower limb is a common and threatening condition whose clinical diagnosis is known to be unreliable. Sonography has gradually superseded venography as the primary diagnostic procedure. A review of the medical literature shows that sonography offers a high level of sensitivity and specificity in symptomatic patients but suffers from a lack of sensitivity at the calf level and in asymptomatic patients. Technologic progress, as well as increased operator experience, may improve sensitivity. Nevertheless, several critical issues remain unresolved, such as the significance of free-floating thrombi, the usefulness of calf and bilateral examination, the criteria that are essential to the diagnosis, the risk of compression sonography, and sonography's role in the direct detection of venous emboli.

Acute Disease↗
PubMed1997

Non-invasive quantification of diaphragm kinetics using m-mode sonography.

PURPOSE: The standard conditions of spirometry (i.e., wearing a noseclip and breathing through a mouthpiece and a pneumotachograph) are likely to alter the ventilatory pattern. We used "time motion" mode (M-mode) sonography to assess the changes in diaphragm kinetics induced by spirometry during quiet breathing. METHODS: An M-mode sonographic study of the right diaphragm was performed before and during standard spirometry in eight patients without respiratory disease (age 34 to 68 yr). RESULTS: During spirometry, the diaphragm inspiratory amplitude (DIA) increased from 1.34 +/- 0.18 cm to 1.80 +/- 0.18 cm (P = 0.007), whereas the diaphragmatic inspiratory (T1 diaph) increased from 1.27 +/- 0.15 to 1.53 +/- 0.23 sec, (P = 0.015, without change in diaphragmatic total time interval (Ttot diaph). Therefore, the diaphragm duty cycle (T1 diaph/Ttot diaph) increased from 38% +/- 1% to 44% +/- 4% (P = 0.023). The diaphragm inspiratory (DIV) and expiratory (DEV) motion velocity (P = 0.007). CONCLUSION: M-mode sonography enabled us to demonstrate that the wearing of a nose clip and breathing through a mouthpiece and a pneumotachograph induce measurable changes in diaphragm kinetics.

Adult↗
PubMed1997

Flow pulsatility in the portal venous system: a study of Doppler sonography in healthy adults.

OBJECTIVE: The purpose of our study was to describe Doppler sonography patterns of venous flow in the portal system of healthy subjects and to compare pulsatility of flow with subjects' body mass, degree of inspiration, and body position. SUBJECTS AND METHODS: Doppler signals from the main, right, and left portal veins; superior mesenteric vein; splenic vein; and inferior vena cava of 23 healthy adults were prospectively studied. Pulsatility of flow was quantified using an index of venous pulsatility (VPI = [maximum frequency shift-minimum frequency shift]/maximum frequency shift). Antegrade flow peak velocities were also related to ECG tracings the time between two R waves being divided into four equal parts for analysis. The caliber variations of the main portal vein and inferior vena cava were measured with M-mode sonography. Doppler tracings were obtained with subjects in supine and sitting positions and during mid and deep inspiration. The subjects' heights and weights were obtained and the body mass index calculated (weight/[height2]). RESULTS: In the portal vein, the VPI was 0.48 +/- 0.31 (mean +/- SD). Marked pulsatility of venous flow (VPI > 0.5) was found in 12 of 23 subjects. We found an inverse correlation between the VPI and the subjects' body mass index (r = -.76; p < .001). Portal vein pulsatility decreased significantly during sitting (p < .05) and deep inspiration (p < .01). The portal VPI was correlated with caliber variation of the inferior vena cava (r = .59; p < .05). In the portal venous system, antegrade flow peak velocities occurred most often during the third quarter of the cardiac cycle, particularly in the splenic vein. CONCLUSION: Doppler sonography shows pulsatile portal venous flow in healthy adults, especially in thin subjects. This pulsatility has an inverse correlation to body mass. The finding of a pulsatile portal vein needs to be interpreted in clinical context and does not necessarily imply dysfunction of the right side of the heart.

Adult↗
PubMed1997

[The venous valve: non-invasive imaging of its functioning].

B Mode and TM mode Imaging are useful tools to illustrate directly the venous valve motion. Using B Mode, venous valve are echogenic with a particular kinetic as regards its topography. So it's possible to determine in TM Mode a "pseudo-cardiac" valvular motion (jugular vein) and a "pseudo-diaphragmatic" motion for the lower limbs veins. Valvular motion assures unidirectional venous flow.

Humans↗
PubMed1997

[Diaphragm kinetics coupled with spirometry. M-mode ultrasonographic and fluoroscopic study; preliminary results].

Most techniques used so far for the evaluation of diaphragm kinetics are either invasive (electromyography, fluoroscopy), or indirect (respiratory pressures, impedance plethysmography). The aim of this study was to determine whether assessment with ultrasound or fluoroscopy differed, and which technique appeared more suitable in the investigation of quantitative hemidiaphragmatic displacement. Six patients (3 female, 3 male, aged 29 to 40) without respiratory disease were studied during systematic X-Ray chest examination, spirometry, and abdominal sonography. The amplitude of the right diaphragm motion could be measured in all patients with M-mode sonography as well as with fluoroscopy. The vertical ascending motion of the diaphragm measured by M-mode sonography, reached 60% of its maximum amplitude at 50% of inspiratory capacity. There was a significant correlation between the maximum amplitude of diaphragm motion as measured by M-mode sonography (5.8 +/- 0.4 cm; r = 0.89; p = 0.019) or fluoroscopy (5.6 +/- 0.7 cm; r = 0.84; p = 0.036) and the inspiratory capacity (2.73 +/- 0.39 l). M-mode sonography has technical, quantitative and qualitative advantages over fluoroscopy and should be the method of choice in the investigation of suspected diaphragmatic movement disorder. When coupled with other techniques like spirometry, this technique could represent a useful adjunct to functional respiratory studies.

Adult↗
PubMed1996

Angiographic embolization of intrahepatic arterioportal fistula.

We report the case of a posttraumatic arteriovenous fistula between the right hepatic artery and the right portal vein remarkable in that clinical manifestations, including portal hypertension and mesenteric insufficiency findings, appeared latently and progressively worsened. This hepatoportal fistula was diagnosed by Doppler sonography and successfully treated by transcatheter embolization of feeding hepatic artery branch with steel coils. We emphasize the interest of pulsed Doppler in the diagnosis of hepatoportal fistula, in assessment of hemodynamic changes related to the fistula and in follow-up after treatment.

Angiography↗
PubMed1996

Power doppler sonography: basic principles and clinical applications in children.

Power Doppler sonography is a new technique that displays the strength of the Doppler signal in color, rather than the speed and direction information. It has three times the sensitivity of conventional color Doppler for detection of flow and is particularly useful for small vessels and those with low-velocity flow. Power Doppler sonography shows potential for detecting areas of ischemia in the kidney, brain, and prepubertal testis and for demonstrating hyperemia in areas of inflammation. Its increased sensitivity to motion and flash artifact, however, limits its application in children. Power Doppler is useful as an adjunct to conventional color and pulsed Doppler sonography.

Child↗
PubMed1996

Pulmonary gas exchange capacity is reduced during normovolaemic haemodilution in healthy human subjects.

PURPOSE: To test the hypothesis that a physiological compensatory mechanism maintains respiratory gas exchange during normovolaemic haemodilution. METHODS: Pulmonary gas exchange capacity was evaluated in seven healthy subjects by measuring the lung diffusion of carbon monoxide (DLCO). During the measurement, various breath-holding times, inspiratory volumes, and sitting or supine positions, were randomly selected in an attempt to alter pulmonary capillary perfusion. KCO was calculated as the percentage of theoretical values of the ratio of DLCO by alveolar volume and normalized by sex, age, and height. Normovolaemic haemodilution (NH) was performed by bleeding an average blood volume of 1 L with simultaneous Dextran 60 replacement to obtain an haematocrit below 35%. RESULTS: After NH, haemoblogin concentration [Hb] decreased from 14.94 +/- 0.96 to 12.5 +/- 0.98 g.dl-1 (P < 0.001). KCO decreased (P < 0.02) but remained closely correlated to [Hb] at every lung volume (P < 0.02). Breathholding time and body position had no effect. CONCLUSION: Moderate NH impairs pulmonary gas exchange capacity in awake, resting healthy subjects. There is no evidence of any compensatory mechanism since the KCO vs [Hb] relationship is unchanged.

Adult↗
PubMed1996

Pulse wave velocity measurement by cross-correlation of Doppler velocity signals. Application to elderly volunteers during training.

Pulse wave velocity (PWV) measurement is widely used for the indirect assessment of arterial wall distensibility. In order to improve its measurement technique, we built a system performing the calculation of the cross-correlation function of Doppler velocity signals. In 12 normal subjects and 10 patients, the mean difference between duplicate measurements was 0.7 +/- 7.8% (NS). We tested this technique in 15 elderly volunteers before and after a three months training period. Brachial and tibial systolic blood pressure decreased respectively from 18.1 +/- 2.2 kPa to 16.7 +/- 1.9 kPa (p = 0.008) and from 21.1 +/- 3.4 kPa to 18.4 +/- 2.5 kPa (p = 0.003), while lower limb PWV decreased from 8.96 +/- 1.26 to 7.92 +/- 1.22 m.s-1 (p = 0.016). Therefore, automatic PWV measurement using the cross-correlation technique allows to demonstrate training induced changes in PWV, although concomitant changes in blood pressure must be considered in their interpretation.

Adult↗
PubMed1996

Electrophysiologic and proarrhythmogenic effects of therapeutic and toxic doses of imipramine: a study with high resolution ventricular epicardial mapping in rabbit hearts.

Electrophysiologic and proarrhythmogenic effects of imipramine were studied by use of 21 Langendorff-perfused rabbit hearts and high-resolution mapping to analyze epicardial activation of the left ventricle. In 16 hearts, a thin layer of epicardium was obtained by an endocardial cryotechnique (frozen hearts). Five hearts were kept intact (nonfrozen imipramine-treated group). Preparation stability was verified in six frozen hearts. In 10 frozen and in 5 nonfrozen hearts, 0.01, 0.1, 1.0, 2.0 and 5.0 micrograms/ml imipramine were administered. In nonfrozen imipramine-treated hearts, imipramine induced bradycardia at 5.0 micrograms/ml (291.8 +/- 40.5 vs. 495.2 +/- 54.4 msec, P = .02), one A-V block at 5.0 micrograms/ml and two monomorphic ventricular tachycardias (MVT) at 2.0 and 5.0 micrograms/ml. In 4/10 frozen hearts, three MVT were induced at 1.0 microgram/ml imipramine and one MVT at 2.0 micrograms/ml imipramine. All MVT were based on reentry around a line of functional conduction blocks. Imipramine (2.0 micrograms/ml) slowed longitudinal and transversal ventricular conduction velocities at a pacing cycle length of 1000 msec from 71.7 +/- 6.1 to 63.0 +/- 7.7 cm/sec (P = .008) and from 32.9 +/- 2.6 to 27.7 +/- 2.8 cm/sec (P = .009), respectively, and prolonged ventricular effective refractory period from 141.9 +/- 9.3 to 279.1 +/- 112.6 msec (P = .03). Imipramine induced dose- and use-dependent slowing of ventricular conduction velocity facilitating functional conduction blocks and reentrant MVT.

Animals↗
PubMed1995

Scanning electron microscopy of microarterial anastomoses with a diode laser: comparison with conventional manual suture.

A diode-laser (830 nm)-assisted carotid artery end-to-end microanastomosis (LAMA) and a contralateral manual suture anastomosis (CMA) were performed in 70 Wistar rats. The vessel sealing was performed on the left carotid by laser pulses (average 3) of 500 mW power and 4.5 sec exposure time, the beam being focused on a spot of 300 microns diameter (700 W/cm2). The CMA was achieved on the right carotid by six 10-0 stitches. From day 0 to day 210, 40 specimens underwent scanning electron microscopy. The laser impact produced a wall injury of 100 microns in width, with an immediate sealing effect due to protein denaturation and collagen fusion of media and adventitia. The anastomosis became re-endothelialized by day 3, while the longitudinal arrangement of the endothelial cells was restored from day 10 on. In the long term, a thick collagenous meshwork of collagen and elastic fibers maintained the strength of the media, while normal endothelium covered the anastomosis. Inversely, after CMA vessel repair was delayed, and the anastomotic line was more irregular and underlined by medial fibrotic scar. In both anastomoses, the patency rate was 93 percent, with nonlethal complications. The advantages of LAMA vs. CMA were: shorter operating time (13 min/22 min), reduced intraoperative trauma, better healing of endothelium, and a miniaturization of the laser source well adapted to microsurgery.

Anastomosis, Surgical↗