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Biomedical subjects

M Guerrisi

Publications and source records attributed to M Guerrisi.

6 recordsLinked to original sources
PubMed2006

Advanced lung ventilation system (ALVS) with linear respiratory mechanics assumption for waveform optimization of dual-controlled ventilation.

The present paper describes the functional features of an advanced lung ventilation system (ALVS) properly designed for the optimization of conventional dual-controlled ventilation (DCV), i.e. with pressure-controlled ventilation with ensured tidal or minute volume. Considering the particular clinical conditions of patients treated with controlled ventilation the analysis and synthesis of ALVS control have been performed assuming a linear respiratory mechanics. Moreover, new airways pressure waveforms with more physiological shape can be tested on simulators of respiratory system in order to evaluate their clinical application. This is obtained through the implementation of a compensation procedure making the desired airways pressure waveform independent on patient airways resistance and lung compliance variations along with a complete real-time monitoring of respiratory system parameters leading the ventilator setting. The experimental results obtained with a lung simulator agree with the theoretical ones and show that ALVS performance is useful for the research activity aiming at the improvement of both diagnostic evaluation and therapeutic outcome relative to mechanical ventilation treatments.

Computer Simulation↗
PubMed2002

Bioelectrical impedance measures in different position and vs dual-energy X-ray absorptiometry (DXA).

BACKGROUND: Bioelectrical impedance analysis (BIA) is a safe, low-cost, non-invasive, rapid method for the assessment of body composition. It has therefore a great potential to be employed for epidemiological and clinical studies. However, many devices are available to estimate total body water (TBW), fat-free mass (FFM) and fat mass (FM) by bioelectrical impedance measurements. Moreover, bipedal devices allowing measurements in the only standing position are recently developed. They are easy and practical to use without operator, so a large diffusion can be forecasted in fields as sport and diet programs. Comparison of body composition estimation by a bipedal device with bioimpedance devices currently used, using dual-energy X-ray absorptiometry (DXA) as reference method. METHODS: The study was performed on 18 healthy women volunteers, age 32.0+/-10.7 years divided in two groups at different levels of body fatness. A Xitron 4000 impedance analyser, a BIA-101 RJL System, and the bipedal device Tanita were used for comparison. The measurements were performed in standing and supine position for Xitron and RJL devices. DXA measurements were performed with a total body scanner DPX, Lunar. RESULTS: FM and FFM were not statistically different when measured with Xitron and RJL in comparison with DXA, while these variables were significantly different between Tanita and DXA measurements. No significant difference were found between measurements in the supine and standing position with the Xitron and RJL system. CONCLUSIONS: Our results suggest that FM and FFM evaluated by bipedal device Tanita are significantly different from FM and FFM measured by DXA in both normal and obese population.

Absorptiometry, Photon↗
PubMed1985

A new approach to non-invasive quantitative study of hepatic haemodynamics using radiocolloids in vivo.

A non-invasive radioisotopic method for the study of liver haemodynamics is described. Data collected by means of a computerised gamma camera for about 4 min after intravenous administration of 99Tcm human serum albumin colloids were analysed using a new mathematical model formulated on a physiopathological basis. Several quantities of possible clinical interest were determined, namely parameters related to liver blood flows, intrahepatic shunts, the intrahepatic space of distribution of the tracer, transit times and extraction efficiency. Results are not affected, within certain limits, by the shape of the radioactive bolus and, with the exception of extraction efficiency, they appear to be independent of the size of the radiocolloidal particle. The dose employed (3-4 mCi) is comparable with that used in liver scintigraphy. Results in 19 subjects with normal liver function, 45 patients with liver cirrhosis and 7 patients with focal liver lesions were in good agreement, from a quantitative viewpoint, with known physiopathological data, thus validating this method in comparison with other more traumatic and/or less practical techniques, which provide less complete information on liver haemodynamics. The method proposed appears to be sufficiently accurate, reproducible, safe and practical, and may thus be considered suitable for routine use in the assessment of functional aspects of liver perfusion for clinical purposes.

Cysts↗
PubMed1983

On the interpretation of the early part of the liver time-activity curve: double tracer experiment.

A double tracer experiment was performed in one normal subject and in one cirrhotic patient to better understand the tracer kinetics in the liver area during the first minute after injection. From a comparison of the time-activity curves obtained in each subject by subsequent iv administration of a nonextracted and an extracted (colloidal) tracer it was possible to distinguish the contribution due to the transport mechanism through intrahepatic and extrahepatic circulation and that due to reticuloendothelial extraction. Three main phases were identified on the curves and an attempt was made to interpret their significance. Results of the study may be of interest for the development of models which could possibly provide more reliable noninvasive quantitation of liver hemodynamics and reticuloendothelial function with the use of one or both types of tracer.

Hemodynamics↗
PubMed1980

A new automatically controlled electric TAH.

Cardiovascular regulatory mechanisms are implemented by means of a very complex control system involving neural, humoral, and mechanical agents. The state of the art in TAH today reveals that we have passed a stage where we can be satisfied with a 6 or 9 mo survival. Development and implementation of a versatile control theory must be another milestone before a TAH can really serve the prospective patient population requiring such a device. This study reveals the vital role and merits as well as the feasibility of incorporating such a control theory into the device.

Heart, Artificial↗