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Biomedical subjects

G Tosti

Publications and source records attributed to G Tosti.

At least 37 records · Page 2Linked to original sources
PubMed1996

In vitro testing of a left ventricular assist device. Study of the effect of its control strategy on energetic relationships inside the left ventricle.

In this study an original left ventricular assist device is tested on an open loop modular physical circuit reproducing Starling's law of the heart to set an optimal control strategy for heart recovery. It is assumed that the goals of the assistance are reduction of oxygen consumption, external work and improvement of cardiac mechanical efficiency. The assistance is evaluated by the position of a working point on the characteristic surfaces of the ventricle defined by peripheral resistance, atrial pressure and selected variables pertaining to energy (pressure-volume area, external work and cardiac mechanical efficiency). In this frame an optimal assistance for heart recovery is a compromise among different requirements corresponding to a restricted set of control parameters values: driving pressure PZB = 35 kPa and timing values T1 and T2 (systole beginning and systole ending in relation to QRS complex and cardiac cycle duration T) T1 = 0.55.T and T2 = 0.73.T.

Bioelectric Energy Sources↗
PubMed1994

A desk-top computer model of the circulatory system for heart assistance simulation: effect of an LVAD on energetic relationships inside the left ventricle.

The study of the interaction between a pneumatic left ventricle assist device (LVAD), driven with different control strategies, and the cardiovascular system is the subject of this paper. It is performed by a modular numerical model of the cardiovascular system connected to a numerical model of the LVAD. The circulatory system is simulated by a lumped parameter numerical model. The ventricle is represented by a time-varying elastance model to reproduce the Starling law of the heart. The effect of the LVAD on the cardiovascular system is evaluated, on the left ventricle alone, by an open-loop circuit consisting of the models of the ventricle, the LVAD and the arterial tree. The analysis is performed in terms of energy variables (such as external work and oxygen consumption and cardiac mechanical efficiency versus control strategy. The LVAD is driven by different control strategies: a fixed heart rate (with different delays from the onset of the natural ventricle contraction) and a variable heart rate.

Cardiovascular Physiological Phenomena↗
PubMed1992

A modular numerical model of the cardiovascular system for studying and training in the field of cardiovascular physiopathology.

A modular numerical model of the cardiovascular system has been developed to reproduce the most important circulatory phenomena in terms of pressure and volume relationships. It is an easy tool to use, designed to be used with a friendly approach on any IBM or compatible personal computer: it offers a wide selection of graphical and numerical outputs and can be rearranged easily for a particular experiment. A set of subroutines related to different circulatory phenomena has been developed; they can be assembled easily together and communicate with each other by two variables. A full description of the existing subroutines is presented in this paper with three different application examples resulting from the rearrangement of the existing software modules: the first concerns the behaviour of the natural ventricle model itself and can be regarded as a ventricle stand-alone characterization test in terms of preload and afterload sensitivities, the second is related to the use of a pneumatic ventricle instead of the model of the natural ventricle, and the third is a full model of the cardiocirculatory system.

Cardiology↗
PubMed1991

Effect of magnetic fluids on the efficiency of an electromagnetic actuator prototype.

An electromagnetic actuator to substitute ventricular function presents some advantages compared with different energy converters. The drastic reduction of the moving parts leads to greater reliability and an accurate control system can be set up. Its major limitations concern weight, heat dissipation and, finally, the overall pump efficiency which is usually rather low. We investigated the possibility of using magnetic fluids in an electromagnetic actuator. Limitations intrinsic to the magnetic fluids prevent their being used as pumping elements but they can be useful to increase the pump efficiency by reducing losses in the magnetic circuit. A remarkable increase in pump efficiency was attained. It is necessary to point out that in designing the electromagnetic actuator the focus was on the pump efficiency with and without the magnetic fluids more than on its performance.

Electromagnetic Phenomena↗
PubMed1990

Central vision impairment from optic disk drusen in the young.

Reduced visual acuity apparently due to the effects of drusen on the optic nerve is rare. We describe two young patients with central vision impairment from optic disk drusen: a man with a reduction of visual acuity to light perception, a women with a very fast evolution of the drusen, that, not visible at the clinical onset, could be documented in autofluorescence one month later. The appearance of drusen in disks initially diagnosed as pseudopapilledema is supposed to be related to axonal degeneration from abnormal axoplasmic flow.

Adult↗
PubMed1988

Thimerosal: a hidden allergen in ophthalmology.

We report 36 patients with thimerosal-induced follicular allergic contact conjunctivitis. 18 patients had follicular conjunctivitis without eyelid involvement, while 5 patients had follicular conjunctivitis associated with an allergic contact dermatitis of the eyelids; all these patients had been using thimerosal-containing eye drops. A further 13 patients were soft contact lens wearers who became sensitized to their own thimerosal-containing lens solutions. All 36 patients showed a positive patch test reaction to thimerosal, while only 1 of them reacted to an ophthalmic solution. Thimerosal sensitization appears to be clinically relevant in ophthalmic patients.

Adolescent↗
PubMed1987

Audiologic abnormalities in cases of vitiligo.

The audiologic function in 50 patients affected by vitiligo was studied. Eight patients (16%) had sensorineural hypoacusis when first seen by us. The relationships between melanocytes of the inner ear and auditory function are discussed.

Adolescent↗
PubMed1986

Retinal pigment epithelium function in alopecia areata.

Electroretinography (ERG) and electro-oculography (EOG) were performed in 98 patients affected by alopecia areata (AA) free from ophthalmologic disorders, and in 40 healthy subjects, in order to evaluate whether or not the retinal pigment epithelium of AA patients shows bioelectrical changes. ERG was normal. EOG, on the contrary, showed a significantly depressed mean value in the AA patient group. Furthermore, depressed EOG occurred more frequently in patients affected by alopecia totalis or universalis as compared with multiple patchy alopecia. These findings prompt the authors to believe that the melanocytes may play a prominent part in the pathogenesis of AA.

Action Potentials↗
PubMed1985

Ocular abnormalities occurring with alopecia areata.

This study was carried out on 83 patients with alopecia areata. Ophthalmological examinations showed lens changes in 65 patients and alterations in the retinal epithelium in 28 patients. The relationships between pigment cells and hair cycle are discussed.

Adult↗
PubMedDate not supplied

A virtual instrument (VI) for haemodynamic management in ICU and during surgery.

Systolic pressure variations (SPV) during mechanical ventilation and its single components, related to short apnea, reflect changes of the volemic condition of the patient. To introduce their determination during clinical monitoring for different fluid states and for different tidal volumes, they must be computed on-line without introducing interference with standard activities. A system computing on-line systolic pressure variation during mechanical ventilation, connected to standard monitoring devices, has been proposed. It is based on a notebook PC implemented with graphical software comprising a user panel in the form of a virtual instrument and is able to acquire, process and present signals from different instruments utilized in ICU and during surgery. It can be used as a base to assess the ability of computed parameters helpful in clinical decision. The use of a notebook PC and open software allows operators, even if non-expert in computer science, to test and implement this, as well as other innovative tools in clinical practice.

Blood Pressure Determination↗