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Biomedical subjects

P Cluzel

Publications and source records attributed to P Cluzel.

At least 55 records · Page 3Linked to original sources
PubMed1996

DNA: an extensible molecule.

The force-displacement response of a single duplex DNA molecule was measured. The force saturates at a plateau around 70 piconewtons, which ends when the DNA has been stretched about 1.7 times its contour length. This behavior reveals a highly cooperative transition to a state here termed S-DNA. Addition of an intercalator suppresses this transition. Molecular modeling of the process also yields a force plateau and suggests a structure for the extended form. These results may shed light on biological processes involving DNA extension and open the route for mechanical studies on individual molecules in a previously unexplored range.

Chemical Phenomena↗
PubMed1996

Pulmonary artery stenosis and periarteritis nodosa.

A severe arterial stenosis involving the origin of the posterior and anterior basal branches of the right lower lobe artery was discovered in a 86 year-old Caucasian woman who presented with a typical periarteritis nodosa. We believe it was specific because its discovery was concomitant to the diagnosis of periarteritis nodosa and no other cause was obvious.

Aged↗
PubMed1995

A model of the human lumbar vertebral column: a preliminary study.

Finite element modelling of the human lumbar vertebral column employs data-processing procedures for study of the linear and nonlinear elasticity of materials such as are currently used in mechanics or in civil engineering. Thanks to developments in computer science, requiring a close collaboration between doctors and engineers, we put forward in this preliminary study a linear computerised model of the lumbar column comprising 4824 meshes and 6813 nodes. By reducing the simplificatory hypotheses and integrating new parameters, this model as developed is capable of important clinical applications in surgery and ergonomics.

Computer Graphics↗
PubMed1995

Factors influencing cardiopulmonary effects of inhaled nitric oxide in acute respiratory failure.

The aim of this prospective study was to determine factors influencing effects of inhaled nitric oxide (NO) on the pulmonary circulation and on gas exchange in critically ill patients with acute lung injury. Twenty-one hypoxemic patients with acute respiratory failure (PaO2 = 127 +/- 69 mm Hg during intermittent positive pressure ventilation, FiO2 = 1), were mechanically ventilated with 2 ppm NO and pure oxygen. The effect of positive end-expiratory pressure (PEEP) on alveolar recruitment was assessed on an anatomic basis using a high-resolution and spiral thoracic computed tomographic (CT) scan. Four conditions were studied in random order: zero end-expiratory pressure (ZEEP), ZEEP + 2 ppm NO, 10 cm H2O PEEP, 10 cm H2O PEEP + 2 ppm NO. During ZEEP and PEEP, NO significantly decreased pulmonary vascular resistance index (PVRI), mean pulmonary arterial pressure (MPAP), true pulmonary shunt (Qs/QT), and alveolar dead space (VDA/VT) and significantly increased PaO2 (p < 0.01). During ZEEP, NO-induced decreases in PVRI (delta PVRI) and MPAP (delta MPAP) were significantly correlated to baseline PVRI and MPAP (delta PVRI = -0.5 PVRI + 125, r = 0.97, p < 0.01 and delta MPAP = -0.28 MPAP + 4.8, r = 0.69, p < 0.05). These changes were not potentiated by PEEP-induced alveolar recruitment. The NO-induced increase in PaO2 (delta PaO2) was not significantly correlated with baseline PaO2 but was correlated with baseline PVRI (delta PaO2 = 0.11 PVRI + 30, r = 0.67, p < 0.05). In patients in whom PEEP was associated with alveolar recruitment, NO increased PaO2 by 66 +/- 24 mm Hg during ZEEP and by 104 +/- 26 mm Hg during PEEP (p < 0.01). In patients in whom PEEP did not induce alveolar recruitment, the NO-induced increase in PaO2 was similar during ZEEP and PEEP conditions (+70 +/- 15 mm Hg versus +76 +/- 12 mm Hg, NS). In patients with adult respiratory distress syndrome, factors determining NO-induced improvement in arterial oxygenation and pulmonary vascular effects are PEEP-induced alveolar recruitment and the baseline level of pulmonary vascular resistance.

Administration, Inhalation↗
PubMed1995

[The intervertebral disk. Attempt at a "finite element" model].

Intervertebral disk composite model is unsatisfactory definite in biomechanical behaviour despite multiples technics used. Using histologic and histoenzymology it's possible to determinate proportions of collagen fibers in the different parts of the disk. A trustworthy finite element 3D model is proposed and tried by real experiments.

Biomechanical Phenomena↗
PubMed1994

Preliminary opto-electronic study on vertebral movement.

Opto-electronic systems utilising measurement of displacement of skin markers allows study of movement in the living subject. The authors have used this method in a kinematic study of the thoracic and lumbar spine measuring the displacement of skin markers placed over the spinous processes. It was possible to approach the physiological state of these complex movements once the apparatus had been calibrated to the correct level, and the error margins minimised. Repeated measurements confirmed the reliability of this method even if movement of the skin with respect to the bony reference points introduced some margin of error. Three dimensional displacement of the vertebrae were measured during voluntary movements of the spine demonstrating the complex geometry. Since opto-electronics are non-invasive they constitute an important advance in the study of the kinematics of the spine.

Adult↗
PubMed1994

Inhaled nitric oxide in acute respiratory failure: dose-response curves.

OBJECTIVE: To determine the dose-response curve of inhaled nitric oxide (NO) in terms of pulmonary vasodilation and improvement in PaO2 in adults with severe acute respiratory failure. DESIGN: Prospective randomized study. SETTING: A 14-bed ICU in a teaching hospital. PATIENTS: 6 critically ill patients with severe acute respiratory failure (lung injury severity score > or = 2.5) and pulmonary hypertension. INTERVENTIONS: 8 concentrations of inhaled NO were administered at random: 100, 400, 700, 1000, 1300, 1600, 1900 and 5000 parts per billion (ppb). Control measurements were performed before NO inhalation and after the last concentration administered. After an NO exposure of 15-20 min, hemodynamic parameters obtained from a fiberoptic Swan-Ganz catheter, blood gases, methemoglobin blood concentrations and intratracheal NO and nitrogen dioxide (NO2) concentrations, continuously monitored using a bedside chemiluminescence apparatus, were recorded on a Gould ES 1000 recorder. In 2 patients end-tidal CO2 was also recorded. RESULTS: The administration of 100-2000 ppb of inhaled NO induced: i) a dose-dependent decrease in pulmonary artery pressure and in pulmonary vascular resistance (maximum decrease--25%); ii) a dose-dependent increase in PaO2 via a dose-dependent reduction in pulmonary shunt; iii) a slight but significant decrease in PaCO2 via a reduction in alveolar dead space; iv) a dose-dependent increase in mixed venous oxygen saturation (SVO2). Systemic hemodynamic variables and methemoglobin blood concentrations did not change. Maximum NO2 concentrations never exceeded 165 ppb. In 2 patients, 91% and 74% of the pulmonary vasodilation was obtained for inhaled NO concentrations of 100 ppb. CONCLUSION: In hypoxemic patients with pulmonary hypertension and severe acute respiratory failure, therapeutic inhaled NO concentrations are in the range 100-2000 ppb. The risk of toxicity related to NO inhalation is therefore markedly reduced. Continuous SVO2 monitoring appears useful at the bedside for determining optimum therapeutic inhaled NO concentrations in a given patient.

Acute Disease↗
PubMed1994

Inhaled nitric oxide reverses the increase in pulmonary vascular resistance induced by permissive hypercapnia in patients with acute respiratory distress syndrome.

BACKGROUND: The aim of this prospective study was to determine if inhaled nitric oxide (NO) would reverse the increase in pulmonary arterial pressures and in pulmonary vascular resistance induced by acute permissive hypercapnia in patients with acute respiratory distress syndrome. METHODS: In 11 critically ill patients (mean age 59 +/- 22 yr) with acute respiratory distress syndrome (Murray Score > or = 2.5), the lungs were mechanically ventilated with NO 2 ppm during both normocapnic and hypercapnic conditions. Four phases were studied: normocapnia (arterial carbon dioxide tension 38 +/- 6 mmHg, tidal volume (655 +/- 132 ml); normocapnia plus inhaled NO 2 ppm; hypercapnia (arterial carbon dioxide tension 65 +/- 15 mmHg, tidal volume 330 +/- 93 ml); and hypercapnia plus inhaled NO 2 ppm. Continuous recordings were made of heart rate, arterial pressure, pulmonary artery pressure, tracheal pressure, and tidal volume (by pneumotachograph). At the end of each condition, arterial pressure, pulmonary artery pressure, cardiac filling pressures, and cardiac output were measured. Simultaneous arterial and mixed venous blood samples were obtained to measure arterial oxygen tension, arterial carbon dioxide tension, mixed venous oxygen tension, arterial hemoglobin oxygen saturation, mixed venous hemoglobin oxygen saturation, pH, and blood hemoglobin and methemoglobin concentrations (by hemoximeter). In addition, plasma concentrations of catecholamines were measured with a radioenzymatic assay. In 5 patients, end-tidal carbon dioxide tension was measured with a nonaspirative infrared capnometer. Calculations were made of pulmonary vascular resistance index, systemic vascular resistance index, true pulmonary shunt, and alveolar dead space. RESULTS: During hypercapnia, NO decreased pulmonary vascular resistance index from 525 +/- 223 to 393 +/- 142 dyn.s.cm-5.m-2 (P < 0.01), a value similar to that measured in normocapnic conditions (391 +/- 122 dyn.s.cm-5.m-2). It also reduced mean pulmonary artery pressure from 40 +/- 9 to 35 +/- 8 mmHg (P < 0.01). NO increased arterial oxygen tension (inspired oxygen fraction 1) from 184 +/- 67 to 270 +/- 87 mmHg during normocapnia and from 189 +/- 73 to 258 +/- 101 mmHg during hypercapnia (P < 0.01). NO decreased true pulmonary shunt during normocapnia (from 34 +/- 3% to 28 +/- 4%, P < 0.001) but had no significant effect on it during hypercapnia (39 +/- 7% vs. 38 +/- 8.5%). In five patients, NO resulted in a decrease in alveolar dead space from 34 +/- 7% to 28 +/- 10% in normocapnic conditions and from 30 +/- 9% to 22 +/- 10% in hypercapnic conditions (P < 0.05). CONCLUSIONS: Inhaled NO completely reversed the increase in pulmonary vascular resistance index induced by acute permissive hypercapnia. It only partially reduced the pulmonary hypertension induced by acute permissive hypercapnia, probably because the flow component of the increase in pulmonary pressure (i.e., the increase in cardiac output) was not reduced by inhaled NO. A significant increase in arterial oxygenation after NO administration was observed during normocapnic and hypercapnic conditions. A ventilation strategy combining permissive hypercapnia and inhaled NO may reduce the potentially deleterious effects that permissive hypercapnia alone has on lung parenchyma and pulmonary circulation.

Administration, Inhalation↗
PubMed1994

Nonpalpable breast tumors: diagnosis with contrast-enhanced subtraction dynamic MR imaging.

PURPOSE: To determine the accuracy of contrast material-enhanced subtraction dynamic magnetic resonance (MR) imaging in the diagnosis of nonpalpable breast tumors. MATERIALS AND METHODS: One hundred forty-three patients underwent surgical biopsy of a nonpalpable breast lesion. Their mammograms showed microcalcifications (n = 80), opacity (n = 52), architectural distortion (n = 10), or asymmetric density (n = 1). All patients underwent a preoperative gadolinium tetraazacyclododecanetetraacetic acid-enhanced subtraction dynamic study. Any early contrast enhancement in the breast parenchyma was considered pathologic. RESULTS: At histologic analysis, 27 intraductal carcinomas, 37 invasive carcinomas, and 79 benign lesions were found. Dynamic MR studies showed early contrast enhancement in 61 of 64 breast cancers (sensitivity, 95%) and in 37 of 79 benign lesions (specificity, 53%). Two invasive lobular carcinomas and one tubular carcinoma showed no early contrast enhancement. CONCLUSION: Subtraction dynamic MR imaging may be helpful to rule out malignancy in nonpalpable breast tumors.

Adult↗
PubMed1994

Stenoses of renal branch arteries in fibromuscular dysplasia: results of percutaneous transluminal angioplasty.

PURPOSE: To evaluate percutaneous transluminal renal angioplasty (PTRA) in the treatment of renal branch artery stenoses caused by fibromuscular dysplasia. MATERIALS AND METHODS: The authors retrospectively studied the files of 20 consecutive hypertensive patients with 25 branch artery stenoses associated with 10 main renal artery lesions. Results at clinical and angiographic follow-up were assessed by means of life-table analysis. RESULTS: PTRA was technically successful in 21 of the 25 renal branch artery stenoses (84%). One of the technical failures was treated by means of selective embolization. Nine of the 10 associated main renal artery lesions were successfully dilated, and the 10th was improved. Immediately after PTRA, at 6-month follow-up, and at long-term follow-up, 70%, 76%, and 68% of the patients, respectively, were cured and 25%, 24%, and 16% were improved. Stenosis recurred in 9% of the branch arteries and was associated with clinical relapse; these arteries were redilated, and all patients were considered cured at the second 6-month follow-up. CONCLUSION: PTRA should be considered the first-line treatment for hypertension due to renal branch artery stenosis in fibromuscular disease.

Adolescent↗
PubMed1994

[Sequencing of DNA by mechanical opening of the double helix: a theoretical evaluation].

We propose and evaluate a model experiment, in which the sequence of a DNA fragment is determined by mechanically opening the double helix in a controlled manner (e.g. pulling on the 3' end of one strand), and measuring the variation of the force exerted by the base pairs on a nanodynamometer (e.g. on a bead in an optical trap or a glass microneedle attached to the 5' end of the other strand). We show that the major limitation of the approach is the longitudinal elasticity of the already sequenced single strand sections, which soften the displacement-force function, and facilitate spontaneous thermal opening of the base pairs.

DNA↗
PubMed1993

High-resolution CT for specific diagnosis of diffuse chronic infiltrative lung disease.

High-resolution CT is highly contributive for correctly diagnosing chronic infiltrative lung disease, as it enables better interobserver agreement, it reveals more discriminant findings, and it provides complementary information. High-resolution CT should be considered an excellent extension to chest radiography and should be included in the routine investigation strategy of chronic infiltrative lung disease.

Humans↗
PubMed1992

Arteriovenous fistula of the internal maxillary artery in a child: case report.

Direct arteriovenous fistulae supplied by the external carotid artery are unusual. Rarely, congenital fistulae have been described involving the head and neck. We describe the first case of congenital internal maxillary arteriovenous fistula in a child. Balloon embolization is currently considered the method of choice for treatment of direct arteriovenous fistula.

Arteriovenous Fistula↗
PubMed1992

Pulmonary sarcoidosis: CT assessment of lesion reversibility.

By comparing serial computed tomographic (CT) scans obtained when sarcoidosis was clinically active and after the onset of remission, an attempt was made to differentiate inflammatory from fibrotic lesions in the lungs of patients with sarcoidosis. Twenty patients with pulmonary infiltration seen on their chest radiographs were studied. For each patient, lesions found on the first CT scan were assessed by two observers as being decreased or increased on the second CT scan. Nodules (n = 8), irregularly marginated nodules (n = 5), and alveolar or pseudoalveolar consolidation (n = 5) always disappeared or clearly decreased. Septal lines (n = 10), nonseptal lines (n = 9), and lung distortion (n = 7) remained unchanged or increased. Some findings varied among patients: Micronodules (n = 9) and subpleural thickening (n = 5) disappeared or decreased in sarcoidosis of recent origin. Many findings of pulmonary infiltration seen on the first CT scan can be considered expressions of either inflammatory (reversible CT findings) or fibrotic (irreversible CT findings) lesions.

Adolescent↗
PubMed1991

[Revascularization of occluded renal arteries. A case].

After recent treatment with an angiotensin converting enzyme inhibitor, a 62-year old woman with diabetes, hyperlipidemia and hypertension was admitted for oliguric acute renal failure due to bilateral renal artery lesions (right stenosis and left thrombosis). Hemodialysis was instituted. Percutaneous transluminal angioplasty (PTA) of the right renal artery did not improve the patient's condition, whereas left renal PTA, three weeks after admission, restored diuresis and renal function, allowing hemodialysis to be discontinued. This case underlines the capacity of functional recovery after late recanalization of a totally occluded renal artery. The best outcome predictor is the development of a collateral circulation and the visualization of distal renal arteries at arteriography. The kidney can be recanalized by surgery or PTA.

Angioplasty, Balloon↗
PubMed1991

[Contribution of imaging in the diagnosis of interstitial fibrosing lung diseases].

Standard radiography of the chest shows pulmonary infiltration and is determinant for the diagnosis of chronic diffuse infiltrative lung diseases. Since lung biopsy is an invasive exploratory technique, using computed tomography (CT) in the diagnostic approach is perfectly justified as a direct prolongation of plain radiography. CT identifies patients who, in spite of normal chest X-ray films, do have pulmonary infiltration. It is superior to radiography in suggesting the correct aetiological diagnosis, as it provides signs that are more discriminant than the radiographic signs. It also gives a better approach to the localization of lesions, thereby helping in guiding lung biopsies. Finally, once the diagnosis has been made CT remains useful in evaluating the effects of treatment of pulmonary lesions and in detecting possible complications.

Humans↗
PubMed1991

Chronic diffuse interstitial lung disease: diagnostic value of chest radiography and high-resolution CT.

The diagnostic value of chest radiography and high-resolution computed tomography (CT) in chronic diffuse interstitial lung disease (CDILD) was assessed in 140 consecutive patients with diffuse infiltration of the lung visible at radiography. Radiographs and CT scans were separately read by three independent observers without knowledge of clinical and pathologic data. The observers listed the three most likely diagnoses and recorded the degree of confidence they had in their choice on a 0%-100% probability scale. Findings at radiography and high-resolution CT were recorded by each observer and were used for a stepwise discriminant analysis between diagnoses. First-choice diagnoses of all three observers that were made with a high level of confidence (probability, greater than or equal to 75%) were more accurate with CT than with radiography (P less than .001). The superiority of high-resolution CT over radiography was most obvious for histiocytosis X and sarcoidosis; in cases of pulmonary fibrosis, CT was not significantly different from radiography. The interobserver agreement for the proposed diagnosis was significantly better with high-resolution CT (P less than .001). Twenty-one of 26 radiographic findings and 21 of 25 CT findings were discriminant. Stepwise discriminant analysis revealed the superiority of CT over radiography, since the ranking of all findings showed that the four most discriminant findings, and eight of the first 12 findings, were revealed with CT.

Adolescent↗