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M Chauveau

Publications and source records attributed to M Chauveau.

At least 19 recordsLinked to original sources
PubMed2001

Modeling of the deformation of flexible tubes using a single law: application to veins of the lower limb in man.

The topic of this study mainly concerns a representative model of the behavior of flexible ducts such as elastic tubes or veins. This model is based on a phenomenological approach of the inflation and collapse of the tube. It leads to a single "universal" analytical expression of the tube law, valid fir a wide range of' positive and negative transmural pressures, which presents a significant improvement compared to previous theoretical studies defined with different expressions on restricted ranges of pressure. Moreover, the theoretical approaches most often require simplif'ing hypotheses--no longitudinal tension, no surrounding tissues--which are quite unrealistic both in the physiological case and in the experimental setup. These theoretical models can therefore be expected only roughly to describe the actual behavior of such vessels. The representative model, on the contrary, allows one to account for the deformation--inflating as well as collapse--of elastic tubes or veins with better accuracy. The tube law is a function of six parameters chosen in order to fit the experimental data. A comparison between results obtained in our laboratory using silicone tubes and representative models is presented. The model is then applied to physiological data obtained in vivo on human leg veins.

Elasticity↗
PubMed1997

[Coronary angiography by left radial approach. A bi-center prospective pilot study].

The aim of this study was to assess prospectively the feasibility, safety and quality of coronary angiography performed by a left radial arterial approach. The investigation was performed under local anesthesia with a Lidocaine gel using Judkins 5f catheter. A bolus of heparin was injected intravenously at the start of the procedure (no heparin in phase 0.2 to 3.000 IU during phase 1 and 5.000 IU in phase 2). Between March 1994 and January 1996, after exclusion of 108 patients (15.1%) mainly because of an abnormal Allen test, coronary angiography was carried out in 540 patients aged 58.4 +/- 11.7 years, 85% of whom were men. The failure rate was 8%. The quality of opacification of the left coronary artery (scale 1 to 3) was 2.91 +/- 0.27 and of the right coronary artery was 2.96 +/- 0.18. There were no complications during the procedure. Analysis of the learning curve showed a failure rate decreasing to less than 5% after 60 procedures/operator. In the last 100 procedures, the failure rate fell to 3%, the canulation time was 2.2 +/- 2.5 min, the duration of fluoroscopy was 6.5 +/- 3.9 min and the duration of the procedure was 17.5 +/- 4.7 min (14.7 +/- 3.8 min, p < 0.01, by the femoral approach). Clinical and Doppler ultrasonographic follow-up revealed one in-hospital complication (a spontaneously regressive compressive haematoma). No clinical complications were observed at 3 months. Doppler ultrasonography showed the radial artery occlusion rate to be 71% in phase 0.32% in phase 1 and 3.2% in phase 2 (p < 0.0001). These results show that the left radial arterial approach for coronary angiography is safe and effective but requires a period of training. A 5.000 IU dose of heparin limits the risk of radial artery occlusion to 3%. The absence of complications in this large series which included the training period and the patient comfort suggest that this technique may be an excellent alternative to the femoral approach and especially the brachial approach when the Allen test is normal.

Aged↗
PubMed1996

Left radial approach for coronary angiography: results of a prospective study.

Although radial approach has been shown to be feasible for coronary angiography, angioplasty, and even stent placement, there have been no prospective evaluations of ease and safety of left radial approach for coronary angiogram. We examined procedural duration and success as well as complications in 415 consecutive patients. Radial artery occlusion was assessed immediately post-procedure and at 2 month follow-up using echo-Doppler measurements. Procedure failure rate was 9%, mean time for sheath insertion was 4.7 +/- 4.7 min, and mean procedure duration was 19.1 +/- 8.2 min. No major complications occurred. Asymptomatic radial artery occlusion was noted in 71% of the first 49 patients, decreased to 24% in the next 119 receiving 2,000-3,000 units of heparin, and to 4.3% in the last 210 receiving 5000 (p < 0.05). Comparison with the femoral approach in the same laboratory suggested that the radial approach took longer, but provided similarly high-quality results without great difficulty in coronary cannulation. Hence, the left radial approach for coronary angiography (with heparin administration) allows immediate ambulation and may be especially useful for outpatients and when the femoral approach is not possible.

Aged↗
PubMed1994

[Drug treatments of chronic venous insufficiency: pharmaco-clinical evaluation].

There are many methods for the assessment of venotropic drugs. Clinical trials based on randomized comparison with placebo are essential. The different methodes used for the evaluation of the functional effects are chosen on the basis of their performance and pertinence for the study objectives. These include three aims which we feel are essential: increased venous tone, decreased capillary permeability and reversal of microcirculatory impairment. Calf plethysmography is highly adapted for the evaluation of venous tone. The mercury gauge works well, but the future will tell if air plethysmography is more adapted here. For capillary permeability, fluoresceine angioscopy is without a doubt the most sensitive and specific method. Unfortunately many laboratories do not have this equipment. If it is not available, the suction cup test or the Landis isotope test may be used although these tests have their limits. For impaired microcirculation, the most interesting test is the laser-Doppler; the results are well correlated with the severity of the chronic venous insufficiency and return to normal after treatment. TcPO2 and capillaroscopic measurements are less sensitive, but are useful in severe cases. Other investigations may be important in individual cases depending on the impact of the medication under study. Drug-induced serum fibrinolytic activity can be measured by the euglobulin lysis time. A haemorheologic effect can be assessed with routine assays (Haematocrit, serum fibrinogen) and measured with tests of red cell deformability and erythrocyte agreggation capacity.

Blood Viscosity↗
PubMed1994

Inhibition of substance P-induced microvascular leakage by inhaled methoxamine in rat airways.

1. The effect of the inhaled alpha-adrenoceptor agonist, methoxamine (MTX), was studied on experimental airway oedema induced by injection of substance P (SP) in the rat. Sprague-Dawley rats (300-350 g) were anaesthetized with sodium thiopentone, tracheotomized and artificially ventilated. 2. MTX or its vehicle was administered by inhalation. Airway resistance and blood pressure were monitored continuously. Evans Blue dye (EB, 20 mg kg-1) was injected through a jugular catheter 1 min before SP (14.8 nmol kg-1). Airways were dissected out, weighed and placed in formamide for EB extraction and determination by spectrophotometry. 3. EB extravasation induced by SP was significantly reduced in distal intraparenchymal bronchi by inhaled MTX at doses of 50 micrograms kg-1 (58 +/- 9 vs 96 +/- 9 ng EB mg-1 tissue after vehicle, P < 0.001) and 100 micrograms kg-1 (69 +/- 11 vs 137 +/- 26 ng EB mg-1 tissue after vehicle, P < 0.01). Inhaled MTX by itself (100 micrograms kg-1) increased blood pressure: 172 +/- 6 vs 132 +/- 10 mmHg baseline (P < 0.02), but neither induced extravasation nor increased airway resistance. 4. In another set of experiments without SP, MTX was administered intravenously 1 min after EB. At 100 micrograms kg-1, i.v. MTX increased blood pressure to a similar extent as inhaled MTX (180 vs 147 mmHg baseline, P < 0.01), increased airway resistance and caused leakage of plasma proteins in distal intraparenchymal bronchi (79 +/- 7 vs 47 +/- 1 ng EB mg-1 tissue, P < 0.02). 5 Similarly, after sequential i.v. injections of doubling doses of MTX (50-800 microg kg-1), a marked EB extravasation was found in the airways. This was abrogated by pretreatment with prazosin (100 microg kg-1)but not with propranolol (2 mg kg-1).6 These results suggest that microvascular leakage and airway oedema induced by i.v. MTX may be linked to an increase in pressure in the pulmonary circulation, resulting from vasoconstriction of the pulmonary vasculature and acute cardiac dysfunction due to systemic hypertension.7 Our results with inhaled MTX show that direct deposition of MTX at the bronchial vasculature induces a reduction in SP-induced microvascular leakage in rat airways and that inhaled MTX does not share the untoward effect of i.v. MTX inducing airway oedema.

Administration, Inhalation↗
PubMed1992

Bronchial provocation tests in small animals: a quantified and automated procedure.

Bronchial provocation tests using aerosols in laboratory animals are difficult to standardize and quantify, because the amount of drug actually reaching the airways is unknown. To improve the quantification of aerosolized inhaled stimuli, we designed an apparatus that allows, in anesthetized intubated ventilated animals, control of temperature and hygrometry of inspired air, computerized measurement of pulmonary resistance, and fully automated delivery of a known amount of aerosolized drug directly into the trachea. Calibration of the aerosol delivery involved direct measurement of liquid delivered at the tip of the tracheal cannula. Despite all our efforts at standardization and full automation of all steps, reproducibility of aerosol delivery was poor, with stroke-by-stroke differences of 26 or 42%, according to whether an air-jet or an ultrasonic nebulizer was used. Histamine dose-response curves performed in 15 guinea pigs with this device confirmed marked differences among animals and also disclosed large intraindividual changes in bronchial responsiveness.

Aerosols↗
PubMed1988

Breathing dry air causes acute epithelial damage and inflammation of the guinea pig trachea.

Drying and cooling of the airways mucosa caused by respiratory water loss may be responsible for exercise- and hyperventilation-induced asthma. Therefore we designed this study to investigate whether breathing dry air is capable of causing structural changes of the airways mucosa. Anesthetized guinea pigs breathed spontaneously through a tracheostomy either dry (n = 15) or water-saturated (n = 12) air at approximately 38 degrees C for 30 or 60 min, during which time total pulmonary resistance (TPR) was measured. Immediately afterward, the animals were killed and the lungs and airways were prepared for histological examination (light microscopy, transmission electron microscopy, and scanning electron microscopy). With dry as well as humid air, there was no change in TPR or in the structure of the main bronchi and lung parenchyma. With humid air the tracheal mucosa was normal in six guinea pigs and exhibited minor changes of the ciliae in eight and localized epithelial damage on light microscopy in the remaining animal. With dry air we found widespread loss of the ciliae on scanning electron microscopy in 10 of 12 animals, associated with detachment or sloughing of the epithelium, subepithelial vascular congestion, edema, and cellular infiltration on light microscopy. Our data demonstrate that a short exposure of the trachea to dry air causes marked epithelial lesions and local inflammation.

Air↗
PubMed1987

The arteriovenous fistula in segmental pancreatic transplantation in dogs--a hemodynamic study.

Arterial and/or venous thrombosis is a frequent complication in experimental or human pancreatic transplantation. A canine experiment was used to study the hemodynamic effects of spleno-splenic arteriovenous fistula during segmental pancreatic transplantation. An increase in blood flow, without "steal" syndrome in the pancreatic blood supply or pressure increase, was found. Thus this technique can help prevent vascular thrombosis in pancreatic transplant in dogs.

Animals↗
PubMed1986

[Doppler study in algodystrophy. Apropos of 10 cases].

Algodystrophy is usually attributed to disorders of microcirculation, and one may reasonably expect to demonstrate these by the Doppler method applied to arteries. Ten patients with algodystrophy stage I were explored and compared with 10 healthy controls and 10 patients with diseases likely to encourage the development of algodystrophy. Systolic, diastolic and mean blood flow velocities were recorded at different levels in the limbs involved and compared with velocities recorded at the same levels in the limbs of healthy subjects and in the clinically healthy limb of control patients. Algodystrophic patients actually had local circulatory abnormalities consisting of an increase in mean velocity with a diastolic component. A diastolic velocity superior to 3 cm/sec on the main arterial axis of the affected limb, or a difference of more than 5 cm/sec in mean velocity between the right and left sides provided an early diagnosis of algodystrophy with an 80 p. 100 sensitivity in this small series. Moreover, in 3 out of 10 cases Doppler velocimetry demonstrated abnormalities at varying levels of the contralateral limb.

Adult↗
PubMed1985

Quantitative Doppler blood flow measurement method and in vivo calibration.

Femoral blood flow (FBF) was measured in seven dogs, simultaneously with both an electromagnetic perivascular probe and a transcutaneous range gated Doppler velocimeter. Measurements were made in basal conditions and during intraarterial infusions of noradrenaline (10 to 400 ng . kg-1 . min-1) and isoprenaline (10 to 400 ng . kg-1 . min-1) thus allowing comparisons of ultrasonic (DBF) and electromagnetic (EMBF) blood flow at 91 different blood flow rates ranging from 5 to 300 cm3 . min-1. The linear regression line through the data of ultrasonic and electromagnetic simultaneous measurement was: DBF = 0.8 + 1.016 EMBF +/- 19.0 cm3 . min-1 with a highly significant correlation (r = 0.96, p less than 0.001) but there was a wide scattering about the mean. Errors in DBF were mainly due to positioning of the probe and determination of arterial diameter.

Animals↗
PubMed1977

[Effect of catecholamines in blood flow in arteries of distribution].

In large arteries, distributing blood to an area (hind leg of dog), the vasomotor substances (catecholamines) induce differences in flow. In case of state of vasoconstriction, the mean velocity of flow decreases, while the amplitude of pulsatile flow and the pressure increase. The radial expansion is wider. In case of state of dilatation, inverse reactions are observed.

Animals↗
PubMed1977

[Effect of localized heat on blood flow in arteries of distribution].

In large arteries distributing blood to an area (hind leg of dog), local heat induces a vasodilatation. The mechanical reactions (variations of mean velocity of flow and amplitude of pulsatile flow) express a distal dilatation. Radial expansion responds in original way (pulsation become uniform).

Animals↗
PubMedDate not supplied

[What information can digital plethysmography provide in acrosyndromes?].

Digital plethysmography records digital pulsation and measures blood flow by occlusion and perfusion pressure. The pulsatile curve is modified in vasomotor disorders of the extremities, and is delayed and flattened in obstructive arteriopathy. In Raynaud's phenomenon, the basal flow (at 22 degrees C) decreases with clinical severity, and suppression of post-ischemic blood flow by cold seems to be an attribute of Raynaud's disease. Digital perfusion pressure is usually greater than or equal to 70% of the humeral systolic pressure. When it decreases under hot conditions, organic obstructive arteriopathy is indicated; decreases due to local cooling allow quantification of hyperreactivity to cold of the digital artery.

Cyanosis↗