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1.
Cerebral CO2 vasoreactivity evaluation by transcranial Doppler ultrasound technique: a standardized methodology 总被引:2,自引:0,他引:2
Objective: In normal subjects cerebral CO2 vasoreactivity is measured during spontaneous hyperventilation, breathholding, or adding CO2 to inspiratory gases. The correlation between CO2 and cerebral blood flow may, however, be invalidated by the effects of a modified respiratory pattern on venous return, sympathovagal balance, and cathecolamine release. Moreover, the duration of the test, usually not considered, may play an important role. This may justify the scattering of values found in literature. We evaluated a new standardized method for overcoming these confounding factors.¶Design: Experimental.¶Participants: Twenty-one healthy volunteers.¶Methods: Subjects were connected through a mouthpiece to a mechanical ventilator set in the intermittent positive pressure ventilation mode. The ventilator was fed by two 40-l tanks, one of which contained 5 % CO2. The inspiratory CO2 concentration was varied at fixed time intervals from 0 % to 5 % without modifying ventilator settings. End-tidal CO2 was measured at the mouthpiece. Mean blood velocity (Vm) and pulsatility index (PI) in the middle cerebral artery were measured by means of transcranial Doppler ultrasound.¶Results: The test was easily applicable and well tolerated. No hemodynamic alterations were observed during the tests. The correlation between CO2 and Vm was always linear and highly significant (R 2 > 0.8, p < 0.0001). A low intersubject variability was observed. No difference was found between the two hemispheres, nor between the sexes.¶Conclusions: The strict standardization of the technique, avoiding hemodynamic interference, may explain the low intersubject variability. The value of this technique in ventilated neurosurgical patients is still speculative, but it might allow the collecting of valuable data together with a reduction in exposure to CO2, and hence cerebral blood flow modifications. 相似文献
2.
Michele Umbrello Giovanni Mistraletti Davide Corbella Marco Cigada Silvia Salini Alberto Morabito Gaetano Iapichino 《Journal of critical care》2012
Purpose
Within the evidence-based medicine paradigm, randomized controlled trials represent the “gold standard” to produce reliable evidence. Indeed, planning and implementing randomized controlled trials in critical care medicine presents limitations because of intrinsic and structural problems. As a consequence, observational studies still occur frequently. In these cases, propensity score (PS) (probability of receiving a treatment conditional on observed covariates) is an increasingly used technique to adjust the results. Few studies addressed the specific issue of a PS correction of repeated-measures designs.Materials and Methods
Three techniques for correcting the analysis of nonrandomized designs (matching, stratification, regression adjustment) are presented in a tutorial form and applied to a real case study: the comparison between intravenous and enteral sedative therapy in the intensive care unit setting.Results
After showing the results before and after the use of PS, we suggest that such a tool allows to partially overcoming the bias associated with the observational nature of the study. It permits to correct the estimates for any observed covariate, while unobserved confounders cannot be controlled for.Conclusions
Propensity score represents a useful additional tool to estimate the effects of treatments in nonrandomized studies. In the case study, an enteral sedation approach was equally effective to an intravenous regime, allowing for a lower level of sedation and spare of resources. 相似文献3.
Ferdinando Bottoni Emanuele Perego Pietro Airaghi Mario Cigada Sergio Ortolina Giuseppe Carlevaro Vito De Molfetta 《Albrecht von Graefes Archiv fur klinische und experimentelle Ophthalmologie》1999,237(7):573-582
· Background: A study was carried out to elucidate the anatomical and functional outcome after surgical excision of subfoveal
choroidal neovascular membranes in high myopia. · Methods: Sixty-five patients with high myopia (≥6 diopters), well-defined
subfoveal neovascular membranes on fluorescein angiography and preoperative visual acuity ≤20/100 were selected for surgery.
A standardized surgical technique was used in all cases, by a single surgeon. The main outcomes assessed were Snellen visual
acuity, surgical retinal pigment epithelium defect and postoperative perfusion of the choriocapillaris. Multifactor analysis
of variance and chi-square/Fisher’s exact test statistics were used to assess the association between patients’ pre- and postoperative
characteristics and outcome measures. · Results: Follow-up ranged from 6 to 48 months (mean 16 months). Mean postoperative
visual acuity (0.18) was significantly better than mean preoperative visual acuity (0.09). Visual acuity improved by at least
two lines in 29 eyes (45%) and was unchanged in 24 (37%). Overall, 43 eyes (66%) had visual acuity of 20/200 or better and
15 (23%), 20/60 or better. Predictive factors with a significant effect on final visual acuity were mean visual acuity, preoperative
status of retinal pigment epithelium and postoperative perfusion of the choriocapillaris. Postoperative perfusion was detected
in 31 (48%) of the total 65 eyes and in 12 (67%) of the 18 eyes with normal retinal pigment epithelium at baseline. The mean
postoperative retinal pigment epithelium defect was 4.6 times larger than the original neovascular membrane. In selected patients,
SLO macular scotometry showed areas of retained retinal sensitivity within the atrophic scar. · Conclusion: The natural history
of subfoveal neovascularization in high myopia is rarely visually restorative. By contrast, surgical excision of the membranes
is feasible and may restore visual acuity in selected patients. This therapeutic approach merits a formal multicenter clinical
trial.
Received: 27 August 1998 Revised version received: 9 November 1998 Accepted: 10 November 1998 相似文献
4.
Milani Paolo Mazzola Marco Cigada Mario Massacesi Amedeo Setaccioli Marco Moschini Stefania Ciaccia Stefano Scotti Fabrizio Mantovani Elena Soranna Davide Zambon Antonella Bergamini Fulvio 《Albrecht von Graefes Archiv fur klinische und experimentelle Ophthalmologie》2022,260(9):2847-2857
Graefe's Archive for Clinical and Experimental Ophthalmology - To propose an algorithm of the major and minor diagnostic criteria for macular myopic choroidal neovascularization (mCNV). This... 相似文献
5.
A Cigada G Rondelli B Vicentini M Giacomazzi A Roos 《Journal of biomedical materials research》1989,23(9):1087-1095
The austenitic stainless steels used today for the manufacture of osteosynthesis devices are sensitive to crevice corrosion. In this study the corrosion properties of some duplex stainless steels were evaluated and compared to traditional austenitic stainless steels. According to our results the following ranking was established: 23Cr-4Ni less than AISI 316L less than ASTM F138 less than 22Cr-5Ni-3Mo less than 27Cr-31Ni-3.5Mo less than 25Cr-7Ni-4Mo-N. In particular the results showed that the high-performance 25Cr-7Ni-4Mo-N duplex stainless steel, with high molybdenum and nitrogen contents, can be considered not susceptible to crevice corrosion in the human body. The duplex stainless steels have also better mechanical properties at the same degree of cold working compared with austenitic stainless steels. Hence the 25Cr-7Ni-4Mo-N duplex stainless steel can be considered a convenient substitute of ASTM F138 for orthopedic and osteosynthesis devices. 相似文献
6.
Alloys based on Ni–Ti intermetallics generally exhibit special shape memory and pseudoelastic properties, which make them desirable for use in the dental field as orthodontic wires. The possibility of nickel release from these materials is of high concern, because the allergenicity of this element. The aim of this study was to test pseudoelastic Ni–Ti wires in simulated physiological conditions, investigating the combined effect of strain and fluoridated media: the wires were examined both under strained (5% tensile strain) and unstrained conditions, in fluoridated artificial saliva at 37 °C. Real time electrochemical nickel release testing was performed using a novel application of a radiotracer based method, thin layer activation (TLA). TLA was validated, in unstrained conditions, against adsorptive stripping voltammetry methodology. Control tests were also performed in non-fluoridated artificial saliva. From our research it transpired that the corrosion behaviour of Ni–Ti alloy is highly affected by the fluoride content, showing a release of 4.79 ± 0.10 μg/cm2/day, but, differently from other biomaterials, it does not seem to be affected by elastic tensile strain. The application of the TLA method in the biomedical field appears a suitable technique to monitor in real time the corrosion behaviour of biomedical devices. 相似文献
7.
Visai L De Nardo L Punta C Melone L Cigada A Imbriani M Arciola CR 《The International journal of artificial organs》2011,34(9):929-946
Titanium oxide is a heterogeneous catalyst whose efficient photoinduced activity, related to some of its allotropic forms, paved the way for its widespread technological use. Here, we offer a comparative analysis of the use of titanium oxide as coating for materials in biomedical devices. First, we introduce the photoinduced catalytic mechanisms of TiO2 and their action on biological environment and bacteria. Second, we overview the main physical and chemical technologies for structuring suitable TiO2 coatings on biomedical devices. We then present the approaches for in vitro characterization of these surfaces. Finally, we discuss the main aspects of TiO2 photoactivated antimicrobial activity on medical devices and limitations for these types of applications. 相似文献
8.
Farè S Brunella MF Bruschi G Cigada A Vitali E 《The International journal of artificial organs》2005,28(7):701-710
In the present study, twelve explanted mechanical heart valves (MHVs)with pyrolitic carbon tilting disc and 14 bileaflet MHVs were analyzed to investigate the effects of material properties on valve performance and patients' general health conditions. Optical and scanning electron microscopy was used to investigate material imperfections, wear patterns or damages to housing and occluder components. All analyzed tilting disc valves exhibited wear effects, particularly due to abrasion and impact to both disc and housing. Wear of pyrolitic carbon disc and housing did not influence their in vivo performance. In the bileaflet MHVs, breakaway of the pyrolitic carbon coating sometimes caused malfunctioning and required surgical retrieval of the valve. In all cases, occurrence of clinical symptoms was more likely when wear effects were located in critical areas. The study supports a correlation between the properties of the MHVs material and patients' symptoms. 相似文献
9.
10.