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Biomedical subjects

Philippe Blanc

Publications and source records attributed to Philippe Blanc.

5 recordsLinked to original sources
PubMed2006

Cement/clay interactions-- a review: experiments, natural analogues, and modeling.

The concept of storing radioactive waste in geological formations calls for large quantities of concrete that will be in contact with the clay material of the engineered barriers as well as with the geological formation. France, Switzerland and Belgium are studying the option of clayey geological formations. The clay and cement media have very contrasted chemistries that will interact and lead to a degradation of both types of material. The purpose of this review is to establish an exhaustive list of laboratory experiments so as to identify the reaction sequences in the evolution of both the clay minerals and accessory minerals during their alteration in an alkaline environment. We review the data on clay dissolution kinetics in this environment, and include an invaluable study of natural analogues that allow one to correlate the phenomena in time. The available data and experiments make it possible to construct predictive numerical models. However, as the quality of the data is inhomogeneous, we recommend a continuation of the thermodynamic and kinetic data acquisition. It is obvious that the numerical modeling of the alkaline disturbance will be more relevant if it can combine the advantages of the different detailed models: mineralogical completeness, combined modeling of the clay and cement media, evolution of the porosity, consideration of the pCO2 and all the surface reactions.

Aluminum Silicates↗
PubMed2006

A nonlinear parametric model for phenanthrene sorption.

Two models for phenanthrene sorption prediction are discussed and checked against experimental data. The first model, based on a two-site Langmuir expression, displays too large uncertainties. The second is based on a modified Langmuir relation and provides a better description of the whole dataset. It includes an experimentally derived relation between the site maximal concentration and chemical parameters of the substrate: TOC amount and polarity index (O+N)/C. The model is tested against sorption isotherms of phenanthrene acquired with six different substrates. Calculated values display satisfying accordance with experimental data. Validity of the model is tested with an isotherm that does not belong to the set of data used for the regression, with good results. Some discrepancies may arise from analytical uncertainty and structural aspects not included within the model.

Journal Article↗
PubMed2002

Rational use of antibiotics in the intensive care unit: impact on microbial resistance and costs.

OBJECTIVE: To evaluate the impact of an intensive care unit (ICU) antibiotic-use policy on the microbial resistance in nosocomial infections and costs. DESIGN: Comparative study before and after policy implementation. SETTINGS: An eleven-bed ICU in a general hospital. PATIENTS: All patients admitted for at least 48 h during a 5year period (1994-1998). INTERVENTIONS: In 1995, implementation of an antibiotic-use policy. MEASUREMENTS AND MAIN RESULTS: Patients' general characteristics, incidence of nosocomial infections, antibiotic-selective pressure (the number of days of antibiotic treatment for 1,000 days of presence in the ICU), presence and types of multi-resistant micro-organisms and costs linked to antibiotic use were recorded before (1994) and after implementation of the policy (1995-1998). For each year, patients' general characteristics and the incidence of nosocomial infections were the same. Costs linked to antibiotics use showed a progressive reduction (100% for 1994, 81% for 1995, 65% for 1998). Antibiotic-selective pressure diminished (from 940 days of antibiotic use per 1,000 days (1994) to 610 (1998), p<10(-5)). A statistically significant reduction in nosocomial infections due to antimicrobial resistant micro-organisms was observed (from 37% (1994) to 15% (1998) of nosocomial infections, p<10(-5)) after 3 years of implementation of the policy, essentially due to a reduction in methicillin-resistant Staphylococcus aureus and ceftriaxone-resistant Enterobacteriaceae. Nosocomial infections due to ceftazidime-resistant Pseudomonas species or extended-spectrum ss-lactamase Enterobacteriaceae showed no reduction. CONCLUSIONS: Antibiotic-use policy allowed a reduction in antibiotic-selective pressure, costs linked to antibiotics and selective reduction of nosocomial infections due to antimicrobial resistant micro-organisms.

Algorithms↗
PubMed2002

Evaluation of left ventricular filling pressure by transthoracic Doppler echocardiography in the intensive care unit.

OBJECTIVE: To determine whether Doppler transmitral and pulmonary venous flow pattern is related to left ventricular filling pressures in critically ill patients. DESIGN: Prospective clinical investigation. SETTING: Medical intensive care unit of a university hospital. PATIENTS: Fifty-four mechanically ventilated patients (age, 63 +/- 16 yrs) were investigated via transthoracic echocardiography and Doppler. Main diagnoses were pneumonia (31%), acute exacerbation of chronic obstructive pulmonary disease (24%), congestive heart failure (11%), and poisoning (11%). INTERVENTIONS: Doppler examinations were performed simultaneously with measurements of pulmonary artery occlusion pressure via a right heart catheter. MEASUREMENTS AND MAIN RESULTS: Pulmonary artery occlusion pressure correlated with transmitral peak E-wave velocity (r =.46) and E/A ratio (r =.55). Pulmonary artery occlusion pressure inversely correlated with deceleration time of the transmitral E-wave (r = -.52), pulmonary venous peak S-wave velocity (r = -.37), and systolic fraction of the pulmonary forward flow (r = -.56). An E/A ratio >2 predicted a pulmonary artery occlusion pressure >18 mm Hg with a positive predictive value of 100%. A duration of pulmonary venous A-wave reversal flow exceeding the duration of the transmitral A-wave forward flow predicted a pulmonary artery occlusion pressure >15 mm Hg with a positive predictive value of 83%. A systolic fraction of the pulmonary venous forward flow <0.4 predicted a pulmonary artery occlusion pressure >12 mm Hg with a positive predictive value of 100%. CONCLUSION: Transmitral and pulmonary venous flow patterns measured by transthoracic Doppler echocardiography can be used to estimate the left ventricular filling pressure in critically ill patients.

Adult↗