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Biomedical subjects

P Demo

Publications and source records attributed to P Demo.

At least 19 recordsLinked to original sources
PubMed2006

Size distribution of nuclei in a closed system.

Kinetic equations describing the formation of nuclei from a supersaturated vapor in a closed system are solved numerically to determine the size distribution of nuclei at various times. Depletion of vapor phase during phase transition process is taken into account. Evolution of the size distribution of nuclei is analyzed. Due to the decrease of the supersaturation of the vapor phase, a maximum appears in the size distribution of nuclei, which disappears at sufficiently long time. Supersaturation of the mother phase decreases to a value close to 1.

Journal Article↗
PubMed2005

Duration of nucleation process in supercooled halide melts.

We present a model allowing to estimate the so-called time lag of nucleating halide melts using electrical conductivity measurements. Due to the complex-forming nature of molten halide salts we suppose two basic types of charge carriers in the melt: complexes (playing the role of monomers-building units) and clusters of a newly forming solid phase. Within context of the nonstationary nucleation theory we determined a formula expressing the time dependency of electrical conductivity of such a system and compared this result with the experimental data obtained for the melts of PbBr2, PbCl2, and KPb2Cl5. In terms of this formula the time lag of nucleation may be estimated. This important quantity characterizing the moment from which the nucleated clusters only grow to the macroscopic sizes has been found to be approximately 75% of the total duration of the nucleation process itself.

Journal Article↗
PubMed2003

When the ICU patient refuses vital supports.

The aim of this paper is to discuss the problem of caring for ICU patients who request forgoing of intensive supports; in particular, evaluating their competence and building effective relationships among the patients themselves, their relatives and the health care team. The histories of 2 adult competent ICU patients 2 asked that vital intervention be forgone are presented, together with the discussion of problems posed by such a request and of possible solutions which respect patients' autonomy and bystanders needs. These patients were hospitalized in an Italian general 14 bed ICU. The patients' request were weighted against their prognosis and their view of life, in order to evaluate their reliability. Also the refusal of either treatment or outcome was evaluated, in order to effectively safeguard the patients' interests. The request of one patient was satisfied and he was allowed to die, after all the involved people had understood and accepted the final decision. The second patient, who was somehow forced to undergo intensive treatment, is alive and satisfied with having been cured. In Italy too, autonomy is an increasingly applied principle in end-of-life decisions in ICUs. It is usually tempered by a consideration about the patients' best interest as perceived by involved bystanders.

Cardiopulmonary Resuscitation↗
PubMed1999

Analytical approach to time lag in binary nucleation.

We present an analytical formula for the time required to establish steady state in a nucleating binary system. To test our solution, we evaluate the time lag for a range of activities of both components at the vapor-liquid transition, and show that our result is in much better agreement with a purely numerical simulation than other available analytical formulas, which overestimate the time lag by factors of from 2 to 200.

Journal Article↗
PubMed1993

Heart rate variability and severe brain damage: preliminary data.

Severe brain damage may cause alterations of cardiovascular function: heart rate, particularly, require the integrity of the vagal, sympathetic and central nervous systems. We studied brain-heart functional relation and neurovegetative modulation by spectral analysis of heart rate variability (HRV). This technique allows separate evaluation of the sympathetic and vagal components of heart rate modulation. In order to correlate changes in HRV with brain damage, we performed 45 recordings in 6 patients (5/1 M/F) by means of autoregressive analysis (AAR). All patients were admitted to the ICU for severe brain damage (anoxic, traumatic or vascular). In 4 patients clinical outcome was brain death, in 2 permanent vegetative status. Two different patterns were found: one in patients with brain death, the other in patients with vegetative status. The small number of patients does not allow definitive conclusions from collected data, but that application of spectral analysis of HRV seems to be a useful monitoring of brain damage subjects.

Adolescent↗
PubMed1991

[Propofol in single bolus for treatment of elevated intracranial hypertension].

Eleven patients with intracranial pressure (ICP) above 20 mmHg despite hyperventilation and neurosedation were treated with a bolus of propofol (1.5 mg/kg) i.v. At baseline and 1-2-5-10-15-30-45 minutes after propofol administration we recorded the values of PIC, systolic arterial pressure (SAP) and mean arterial pressure (MAP), heart rate (HR) and cerebral perfusion pressure (CPP), calculated as MAP less PIC. In the first ten minutes after propofol we observed a statistically significant (p less than 0.05) decrease of ICP and SAP. MAP decreased in the first five minutes only. Consequently HR increased at the same time. CPP decreased in the first two minutes after administration of the drug, but without statistical evidence. We conclude that propofol, in our opinion, can be used to treat intracranial hypertension but the hemodynamic effects in hypovolemic patients must be taken into consideration.

Adolescent↗
PubMed1990

Intra-operative monitoring by means of somatosensory evoked potentials during cerebral aneurysms surgery.

During cerebral aneurysms surgery, brain tissue may suffer for global or local ischemia due to deliberate hypotension and surgical manoeuvres. Somatosensory evoked potentials (SEPs) can detect functional derangements consequent to hypoxia, before a permanent brain damage is produced. Forty two patients, undergoing cerebral aneurysms surgery for treatment of SAH, were evaluated intraoperatively with SEP recordings. It has been stressed that no permanent neurological damage is to be expected if the absolute value of Central Conduction Time (CCT) does not exceed 9.5 ms for 10 min at least and the cortical waves are visible throughout the whole procedure. SEP changes are strictly related with MAP decrease and surgical handlings.

Adult↗
PubMed1990

The transcranial Doppler ultrasonography in the evaluation of vasospasm and of intracranial hypertension after subarachnoid hemorrhage.

The transcranial doppler (T.C.D.) is a non-invasive technique useful for the evaluation of vasospasm and intracranial hypertension in patients with subarachnoid hemorrhage (S.A.H.). Eighteen patients with recent S.A.H. were studied by means of T.C.D. device: in 14 patients the source of bleeding was a ruptured aneurysm of the circle of Willis, while the remaining 4 presented a negative four-vessels angiography. All the patients were studied 5 and 10 days after the bleeding. Our data showed that the ultrasonographic demonstration of vasospasm and/or I.C.H. is clearly related to the clinical status of the patients. No significant T.C.D. difference was noticed between the "sine materia" S.A.H. patients and the ones with ruptured aneurysm.

Blood Flow Velocity↗