Separation and preconcentration phenomena in internally heated poly(dimethylsilicone) capillaries: preliminary modelling and demonstration studies.

The concept of achieving low-resolution separations in internally heated capillary membranes is discussed in terms of controlling the diffusion coefficients of volatile organic compounds in poly(dimethylsilicone) membranes in space and time. The behaviour of 1,1,1-trichloroethane in polydimethylsilicone was used in conjunction with a mixed-physics finite element model, incorporating second order partial differential equations, to describe time and spatial variations of mass-flux, membrane temperature and diffusion coefficients. The model, coded with Femlab, predicted highly non-linear diffusion coefficient profiles resulting from temperature programming a 500 [micro sign]m thick membrane, with an increase in the diffusion coefficient of approximately 30% in the last 30% of the membrane thickness. Simulations of sampling hypothetical analytes, with disparate temperature dependent diffusion coefficient relationships, predicted distinct thermal desorption profiles with selectivities that reflected the extent of diffusion through the membrane. The predicted desorption profiles of these analytes also indicated that low resolution separations were possible. An internally heated poly(dimethylsilicone) capillary membrane was constructed from a 10 cm long, 1.5 mm od capillary with 0.5 mm thick walls. Thirteen aqueous standards of volatile organic compounds of environmental significance were studied, and low-resolution separations were indicated, with temperature programming of the membrane enabling desorption profiles to be differentiated. Further, analytically useful relationships in the [micro sign]g cm(-3) concentration range were demonstrated with correlation coefficients >0.96 observed for linear regressions of desorption profile intensities to analyte concentrations.

Carbamazepine-associated severe left ventricular dysfunction.

INTRODUCTION: The cardiovascular effects of carbamazepine are well-known but left ventricular dysfunction is rarely reported. CASE REPORT: We describe 2 cases of severe carbamazepine-associated left ventricular dysfunction during massive self intoxications in young patients without preexistent cardiac disease. We compare our cases to the available literature and discuss the mechanisms implied in the development of left ventricular dysfunction following carbamazepine overdose. Bedside echocardiography was useful in both diagnosis and treatment.

[Use of the helium-oxygen mixture in pneumology practice]. / Utilisation du mélange hélium-oxygène en pratique pneumologique.

Therapeutic use of the helium-oxygen mixture (heliox) was first reported in 1934. Medical use was further restricted to physiological studies. Density and viscosity of Heliox are very different from those of air or oxygen. This can explain how Heliox can induce modifications in the airway flow. In diseases of the main or small airways (upper airway obstruction, chronic obstructive pulmonary disease, asthma), such modifications could induce a diminution in the resistive component of the work of breathing and therefore protect against the risk of developing a respiratory failure. This explains a renewed interest of clinicians for Heliox since the beginning of the eighties. To date, the good tolerance of heliox seems to be well established. Inversely, scientific validation of the therapeutic indications of the mixture in airway diseases are lacking. Moreover, potential therapeutic indications of the mixture are not restricted to airway diseases. Various applications, such as adult respiratory distress syndrome, pneumothorax, fiberoptic bronchoscopy, and mechanical ventilation, are suggested by preliminary reports. Obtaining a synthetic vision of older and more recent studies is the purpose of this review.

[Hemodynamic effects of enoximone and comparison with dobutamine in patients with chronic respiratory insufficiency and pulmonary arterial hypertension]. / Effets hémodynamiques de l'énoximone et comparaison avec la dobutamine chez l'insuffisant respiratoire chronique avec HTAP.

The aim of this study was to assess the effects of enoximone on the right ventricle and pulmonary hypertension in 10 patients (53 to 84 years) with chronic obstructive airway disease resulting in acute or chronic respiratory failure requiring mechanical ventilation in 9 cases. These effects were compared with those of dobutamine. All patients were in sinus rhythm and 6 had signs of right ventricular failure. Haemodynamic and 2D echocardiographic (study of left and right ventricular function) measurements were made under basal conditions (TB1), with 10 micrograms/kg/mn of dobutamine (TDob), again under basal conditions (TB2) three hours after the end of the dobutamine infusion, and then 30 minutes after an intravenous bolus (1 mg/kg) of enoximone (TE1) relayed by an infusion of 10 micrograms/kg/mn at 3 hours (TE2) and at 12 hours (TE3). The results (x +/- SD) were studied by a 2 factor variance analysis and compared by Student's test with Dunnett's correction. Cardiac index increased similarly by about 45% with enoximone (2.8 +/- 0.8 vs 4.1 +/- 1 l/min/m2; p less than 0.001 at TE2) and dobutamine, although the heart rate did not change significantly. Systemic arterial resistance fell significantly with enoximone (31.3 +/- 11 vs 21.3 +/- 6.8 IU; p less than 0.05 at TE2) but mean arterial pressures were unchanged; mean pulmonary artery pressures decreased from TE1 to TE3 (27.6 +/- 6.9 vs 22.6 +/- 6.3 mmHg; p less than 0.05 at TE2) mainly because pulmonary artery diastolic pressures decreased from TE1 to TE3 (20.1 +/- 4 vs 11.1 +/- 5.2 mmHg; p less than 0.05 at TE3).(ABSTRACT TRUNCATED AT 250 WORDS)