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Biomedical subjects

M Dauzat

Publications and source records attributed to M Dauzat.

At least 55 records · Page 3Linked to original sources
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↗
PubMed1995

Pulsed Doppler sonography for the guidance of vein puncture: a prospective study.

Blind deep venous puncture is an invasive procedure with risks of serious complications compromising the availability of veins for future punctures or endangering the patient's life. We designed a new hand-held pulsed Doppler probe for coaxial guidance of the puncture needle and a dedicated pulsed Doppler device displaying the depth of the measurement volume. We used this technique prospectively in two independent centers (the nephrology department and the intensive care unit) involving senior as well as junior staff members. Either the non-Doppler or the Doppler method were randomly selected for subclavian vein catheterization in 100 patients and for internal jugular vein catheterization in 30 patients. The success rate on the first attempt was 86.2% for the non-Doppler method versus 96.8% for the Doppler method (p = 0.03). The failure rate of the non-Doppler method used by junior staff members was 9.2%, reduced to 1.5% (p = 0.05) by secondary use of the Doppler method and/or help from a senior staff member (rescue procedure). Pulsed Doppler guidance reduced significantly the failure rate of venous punctures especially when used by seniors or by juniors after a training period.

Adult↗
PubMed1995

Short- and long-term hemodynamic effects of transjugular intrahepatic portosystemic shunts: a Doppler/manometric correlative study.

OBJECTIVE: The purposes of this study were to evaluate the effect of a well-functioning transjugular intrahepatic portosystemic shunt (TIPS) on the splanchnic and intrahepatic circulation, to determine if sonographic measurements can predict shunt dysfunction before clinical manifestations of portal hypertension occur, and to compare Doppler sonographic findings with portocaval gradient measurements before and after shunt revision. SUBJECTS AND METHODS: Forty-four patients with cirrhosis (n = 43) and myelofibrosis (n = 1) who underwent successful TIPS insertion were included in this prospective study. Indications for TIPS placement were: refractory ascites (24 patients), bleeding esophageal varices (17 patients), portal hypertensive gastropathy (two patients), and bleeding colonic varices (one patient). The portal vein and the inferior vena cava were catheterized; and the portocaval gradient was recorded before TIPS placement, at 2 and 12 months after TIPS placement, and when clinical or Doppler findings suggested shunt dysfunction. Doppler studies were done within 1 week before TIPS placement, within 2 days after TIPS placement, every 2-3 months thereafter, and before and after a TIPS revision. The Doppler studies included flow volume measurements in the portal vein and in the stent, as well as determination of the direction of flow in the segmental branches of the portal vein, in the splanchnic veins, and in portosystemic collaterals. Changes in Doppler findings and in catheter pressure measurements were compared using Spearman's rank correlation test. Significance was set at the .05 level. RESULTS: A marked decrease (-51%) in portocaval gradient was observed after TIPS placement. At Doppler sonography, portal vein velocity and diameter were both higher after TIPS placement, resulting in a marked increase in portal venous flow (170%). Mean flow velocity in the shunt was 55.8 +/- 3.6 cm/sec, and flow volumes in the shunt and in the main portal vein were 1596 ml/min and 1731 ml/min, respectively (p = nonsignificant). Dysfunction of the stent occurred in 27% of the patients. Changes in stent blood flow volume were closely related to changes in the portocaval gradient (r = -0.67, p < .001). Reduction of blood flow volume in the stent or change of direction of flow in intrahepatic portal veins or in collateral veins signaled shunt dysfunction (84% sensitivity, 89% specificity). CONCLUSION: Marked hemodynamic changes in the portal venous system occur soon after a TIPS procedure. Monitoring of shunt function with periodic Doppler sonography, including calculation of shunt blood flow, is useful in detecting shunt dysfunction before clinical signs occur.

Adult↗
PubMed1994

Microarterial anastomosis using a noncontact diode laser versus a control study.

A series of direct carotid end-to-end laser anastomosis vs. direct manual suture was carried out on a series of 70 Wistar rats (mean weight 260 g). Both common carotids (0.8-1.2 mm) were sectioned and repaired. The left side (n = 70) was submitted to laser-assisted microvascular anastomosis (LAMA) performed by means of a diode laser device (wavelength 830 nm and power output 3 W in continuous wave) without chromophore. The right side (n = 70) underwent a control manual suture (CMA). The diode laser energy was delivered into a micromanipulator coupled to a Zeiss operating microscope with a focused spot of 300 microns in diameter. After placement of three 10.0 stitches for edge coaptation, the LAMA was achieved using laser shots (average 3) of 500 mW power, 4.5 s duration, and 700 W/cm2 irradiance each. The CMA was performed by means of six 10.0 stitches. The good vascular flow was confirmed by Doppler spectral analysis (n = 466) carried out from day 0 to day 90. Light and scanning electron microscopy (n = 82) showed that re-endothelialization after LAMA was gaining ground on day 3, whereas collagenous network developed in the media scar by day 10. In contrast, after CMA the arterial repair was delayed on day 20, inducing a media fibrotic scar. The patency rate was 93% in both anastomoses. The shorter operating time (13 min for LAMA vs. 22 min for CMA) and the noncontact laser technique are the main intraoperative advantages. The technical benefits of the diode laser are pointed out.

Anastomosis, Surgical↗
PubMed1994

Meal induced changes in hepatic and splanchnic circulation: a noninvasive Doppler study in normal humans.

The haemodynamic effects of a meal on the splanchnic and hepatic circulation were evaluated in 30 healthy volunteers, using Doppler ultrasonography. The resistance index (RI) of the superior mesenteric artery and of the left and right intrahepatic arteries, the portal vein blood flow as well as the ratio between maximal velocity in the left and right intrahepatic arteries and the adjacent portal vein were measured initially, then 15, 30, 45, and 60 min after the ingestion of a standard balanced liquid meal. Postprandial haemodynamic changes were maximal 30 min after the meal; at that time, mesenteric artery RI decreased significantly [mean -11% (SEM 14%)] whereas portal vein blood flow increased markedly [mean +79% (SEM 14%)]; a significant increase in hepatic artery RI was observed in both liver lobes. The ratio between maximal velocities of the intrahepatic artery and the intrahepatic portal vein was reduced significantly; this ratio decreased more markedly in the right lobe of the liver. These findings would suggest that there was an adaptation of hepatic artery to portal vein blood flow after a meal. The subsequent increase in intrahepatic portal vein flow velocity was found to be greater in the right lobe of the liver.

Adult↗
PubMed1994

Hemodynamic changes after transcatheter arterial embolization of hepatocellular carcinomas.

PURPOSE: To evaluate the serial hemodynamic changes that occur after transcatheter arterial embolization (TAE) of hepatocellular carcinomas (HCCs). MATERIALS AND METHODS: Twenty patients with HCCs treated with TAE were evaluated with color and duplex Doppler sonography before, immediately after, and 2 days after TAE. The changes in hepatic artery and portal vein velocity and flow were evaluated. RESULTS: The portal venous velocity and flow did not change significantly after TAE. The peak systolic velocity in the proximal hepatic artery decreased significantly (P < .01) immediately after TAE then returned to baseline values 2 days after TAE; the resistance index of the proximal hepatic artery increased significantly (P < .01) immediately after embolization, then returned to baseline values 2 days after TAE. Arterial signal in the distal hepatic artery, generally absent immediately after TAE, could be recorded 2 days after. CONCLUSION: There is a rapidly reversible decrease in hepatic arterial flow induced by embolization, without any change in portal venous flow.

Adult↗
PubMed1994

Gas bubble emboli detected by transcranial Doppler sonography in patients with prosthetic heart valves: a preliminary report.

After observing spikes in the Doppler signal of cerebral arteries of patients with neurologic symptoms and prosthetic heart valves, we then studied two groups of patients with prosthetic heart valves: seven patients with neurologic symptoms and 65 asymptomatic patients. Using transcranial Doppler sonography of the middle cerebral artery, we found Doppler spikes in six symptomatic and 24 asymptomatic patients with mechanical heart valves. No spikes were found in one symptomatic and 21 asymptomatic patients with biological valves or in 20 asymptomatic patients with mechanical valves. We concluded that gas cavitation during the opening or closure of the valve, producing bubble emboli, is the most probable explanation for these Doppler spikes in patients with mechanical prosthetic heart valves.

Aged↗
PubMed1994

[Continuous guidance for venous punctures using a new pulsed Doppler probe: efficiency, safety].

Serious complications may occur after "blind" profound venous puncture in intensive care units. To secure these punctures, we designed a new fingertip pulsed Doppler (FPD) 5 MHz probe with a lateral to center indentation to guide the needle into the ultrasonic flux. A specific ultrasound analyzer indicating depth and diameter of the vessel was made for this use. The material was first tested in an experimental animal study. Results of animal venous punctures were successful 20/21. This material was then tested on patients with previous failure of "blind" punctures: results of 4 FPD punctures were successful in all 12 cases but one (catheterization not completed). We started a prospective multi-unit randomized study with various operators (junior residents, senior staff members), compared the success rate and type, the procedure duration of blind standard versus FPD punctures. We conclude in the safety and easy use of the FPD for central venous punctures.

Animals↗
PubMed1993

Hepatic artery: effect of a meal in healthy persons and transplant recipients.

Thirty healthy volunteers and 12 liver allograft recipients (two with cirrhotic changes seen at microscopy) were given a standard meal. Doppler sonography of the right and left hepatic arteries, the superior mesenteric artery, and the portal vein was performed. The change in hepatic arterial resistance was evaluated with the resistive index (RI). After the standard meal, portal venous flow increased in both the healthy volunteers and allograft recipients (more so in the latter group). Superior mesenteric arterial RI decreased in all subjects. A postprandial increase in hepatic arterial RI, likely reflecting constriction of the hepatic artery, was seen in both groups. It was absent in the two patients with recurrent transplant cirrhosis. These results show the importance of examining hepatic arterial flow in the fasting subject, since high resistance after a meal may be falsely interpreted as a sign of disease. Absence of a postprandial change in resistance of the hepatic artery could signal abnormal liver function.

Adult↗