PubMed Health⌕ Search

SEARCH · PubMed Health

Results for “Experimental validation”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 325 records · Page 18Linked to original sources
PubMed2003

Determination of regional flow by use of intravascular PET tracers: microvascular theory and experimental validation for pig livers.

UNLABELLED: Today, the standard approach for the kinetic analysis of dynamic PET studies is compartment models, in which the tracer and its metabolites are confined to a few well-mixed compartments. We examine whether the standard model is suitable for modern PET data or whether theories including more physiologic realism can advance the interpretation of dynamic PET data. A more detailed microvascular theory is developed for intravascular tracers in single-capillary and multiple-capillary systems. The microvascular models, which account for concentration gradients in capillaries, are validated and compared with the standard model in a pig liver study. METHODS: Eight pigs underwent a 5-min dynamic PET study after (15)O-carbon monoxide inhalation. Throughout each experiment, hepatic arterial blood and portal venous blood were sampled, and flow was measured with transit-time flow meters. The hepatic dual-inlet concentration was calculated as the flow-weighted inlet concentration. Dynamic PET data were analyzed with a traditional single-compartment model and 2 microvascular models. RESULTS: Microvascular models provided a better fit of the tissue activity of an intravascular tracer than did the compartment model. In particular, the early dynamic phase after a tracer bolus injection was much improved. The regional hepatic blood flow estimates provided by the microvascular models (1.3 +/- 0.3 mL min(-1) mL(-1) for the single-capillary model and 1.14 +/- 0.14 min(-1) mL(-1) for the multiple-capillary model) (mean +/- SEM mL of blood min(-1) mL of liver tissue(-1)) were in agreement with the total blood flow measured by flow meters and normalized to liver weight (1.03 +/- 0.12 mL min(-1) mL(-1)). CONCLUSION: Compared with the standard compartment model, the 2 microvascular models provide a superior description of tissue activity after an intravascular tracer bolus injection. The microvascular models include only parameters with a clear-cut physiologic interpretation and are applicable to capillary beds in any organ. In this study, the microvascular models were validated for the liver and provided quantitative regional flow estimates in agreement with flow measurements.

Animals↗
PubMedDate not supplied

[Experimental validation of the Evidence-Based Occupational Health paradigm and of the PICO model in the decision making process applied by occupational health physicians].

BACKGROUND: Health care organizations are increasingly aware of the need to apply quality assurance principles to serve their mission and there is an increasing pressure on health professionals to ensure that the practice is based on evidence of appropriateness. Medical specialists of different disciplines, including occupational health, are presently required to shift from habitual practices to evidence-based practices, and have began to use an approach based on the paradigm of Evidence-Based Medicine and of Evidence-Based Occupational Health (EBOH). OBJECTIVE AND METHODS: The study was carried out to analyse how the paradigm of the EBOH could be implemented in the search, analysis and synthesis of the best available evidence to apply in the decision-making process in occupational health practice. Out of 464 medical examinations consecutively performed by 4 occupational health physicians, 6 cases were selected on the basis of their complexity and the need for further investigation. Each case was submitted to each of the 4 physicians, who were asked to make a decision according to the EBOH paradigm: i.e., (i) identification of the problem according to the PICO model, (ii) solution of the problem according to his/her internal evidence or experience (iii) search for scientific external evidence, (iv) critical appraisal of such evidence, (v) application of the evidence in the decision-making process, (vi) comparison between internal evidence and external evidence. Outcome measurements, including satisfaction of the physicians, were collected. RESULTS: No differences were found between the decisions based on external evidence or on internal evidence in about 50% of the cases (13/24). In about 1/3 of the cases (7/24) no agreement was observed between the decisions taken on the basis of internal and external evidence. In some cases (5/24) no useful information was added for the purposes of decision-making. In about 50% of the cases the professionals were satisfied with the information found in databases, due to its usefulness both in increasing their knowledge and in improving their practice. CONCLUSIONS: Due to their involvement in a corporate system, the participants were aware of the need to practice according to quality assurance principles and to relinquish ineffective and obsolete practices. They agreed with the need to search for the best available evidence with the aim of guaranteeing efficacious interventions. In spite of a number of obstacles to the application of the EBOH paradigm to occupational health practice, the study demonstrated that such approach can be successfully applied in this field and that it can be proposed for the search of appropriate solutions to the problems usually encountered in professional practice.

Decision Support Systems, Clinical↗
PubMed2006

Quantification of subendocardial and subepicardial blood flow using 15O-labeled water and PET: experimental validation.

UNLABELLED: The purpose of this study was to assess the feasibility and accuracy of quantifying subendocardial and subepicardial myocardial blood flow (MBF) and the relative coronary flow reserves (CFR) using (15)O-labeled water (H(2)(15)O) and 3-dimensional-only PET. METHODS: Eight pigs were scanned with H(2)(15)O and (15)O-labeled carbon monoxide (C(15)O) after partially occluding the circumflex (n = 3) or the left anterior descending (n = 5) coronary artery, both at rest and during hyperemia induced by intravenous dipyridamole. Radioactive microspheres were injected during each of the H(2)(15)O scans. RESULTS: In a total of 256 paired measurements of MBF, ranging from 0.30 to 4.46 mL.g(-1).min(-1), microsphere and PET MBF were fairly well correlated. The mean difference between the 2 methods was -0.01 +/- 0.52 mL.g(-1).min(-1) with 95% of the differences lying between the limits of agreement of -1.02 and 1.01 mL.g(-1).min(-1). CFR was significantly reduced (P < 0.05) in the ischemic subendocardium (PET = 1.12 +/- 0.45; microspheres = 1.09 +/- 0.50; P = 0.86) and subepicardium (PET = 1.2 +/- 0.35; microspheres = 1.32 +/- 0.5; P = 0.39) in comparison with remote subendocardium (PET = 1.7 +/- 0.62; microspheres = 1.64 +/- 0.61; P = 0.68) and subepicardium (PET = 1.79 +/- 0.73; microspheres = 2.19 +/- 0.86; P = 0.06). CONCLUSION: Dynamic measurements using H(2)(15)O and a 3-dimensional-only PET tomograph allow regional estimates of the transmural distribution of MBF over a wide flow range, although transmural flow differences were underestimated because of the partial-volume effect. PET subendocardial and subepicardial CFR were in good agreement with the microsphere values.

Algorithms↗
PubMed1990

[Experimental validation of the use of RNA hydrolysate (ENKAD) in chemical burns of the cornea].

The influence of ENKAD on the course of a severe alkaline burn of the cornea was studied in 158 rabbits (316 eyes). Cytochemically, regularity in correlations of separate amino acids: cystin, cysteine, arginine and glutaminic acid in cellular proteins of the intact cornea was established and their disorder in dynamics of the burn process is shown. Comparative assessment of therapeutic effectiveness of ultrasound, applications, subconjunctival injections and phonophoresis of ENKAD has shown that a combined usage of ultrasound and ENKAD has the most expressed positive action on the course of the burn process of the corneal burn, such as acceleration of corneal epithelialization that accomplished, on the average, by the 9.3 +/- 0.3 day (in the control--by the 20.8 +/- 1.8 day), rapid disappearance of its perifocal edema--11.05 +/- 0.7 (in the control - 29.7 +/- 1.1) day, better outcomes after the burn (in 37.5% of cases superficial limited opacifications were formed, in the control--in 7.1%). One of the factors of therapeutic action of ENKAD phonophoresis is its normalizing influence on disturbed correlation of amino acids in proteins. The results obtained allow to recommend to include ENKAD phonophoresis into a complex treatment of patients with eye burns.

Animals↗
PubMedDate not supplied

[An experimental validation of the use of various types of allografts for the replacement of mandibular defects].

The intensity of restructuring of various types of bone transplants and reaction of the adjacent tissues of the femoral distal epiphysis to these transplants was studied in rat experiments. The most manifest bone-inducing properties were detected in demineralized allobone, the least so in formalin-treated one; lyophilized and frozen transplants occupy an intermediate position between these two. These data are recommended to be borne in mind when replacing mandibular defects.

Animals↗
PubMed1990

The cavernosal acetylcholine/papaverine response. A practical in vivo method for quantification of endothelium-dependent relaxation. Rationale and experimental validation.

An in vivo method has been developed for quantifying cavernosal endothelium-dependent relaxation. The method is based on the fact that relaxation of the smooth muscle around the sinusoids of the penile corpora cavernosa activates the erectile veno-occlusive mechanism, and the degree of veno-occlusion can be precisely quantified by the pharmacologic maintenance erectile flow (PMEF) method. Pharmacologic maintenance erectile flows are determined after intracavernosal infusion of the endothelium-dependent relaxant acetylcholine (ACh) and the endothelium-independent relaxant papaverine, and expressed as an acetylcholine/papaverine ratio (APR). Control rabbits showed no changes from the test procedures themselves. In 12 test rabbits, control PMEFs after approximately 10(-7) mol ACh or papaverine averaged 0.7 and 0.5 ml/minute, respectively; APR averaged 1.3. Endothelial injury of the corpus cavernosum was produced by intracavernosal injection of 100 micrograms (16 x 10(-8) mol) of the detergent CHAPS or 1 ml of Renografin-76. Within 1 hour of injection of either agent, PMEF(ACh) increased markedly to approximately 6, PMEF(pap) increased minimally to approximately 0.9, and APR increased to about 7. These values gradually decreased to normal limits at six weeks. Endothelial injury and recovery were confirmed by electron microscopy. Thus, reduced cavernosal response to ACh relative to papaverine was indicative of endothelial injury. The ACh/papaverine response ratio offers promise as a practical and reliable in vivo method for quantifying endothelial-dependent relaxation.

Acetylcholine↗
PubMed1990

[An experimental validation of organ-preserving operations in traumatic lesions of the parenchymatous organs].

Resulting from the experiment performed on 32 dogs, the authors have established that the use of technology of tissue bioinhibition and cryogenic influence led to local cryopreservation, hypercoagulation and change in the physical properties of the damaged parenchyma. This contributes to successful performance of the organ preserving operations and prevents the development of early and long-term postoperative complications.

Animals↗
PubMedDate not supplied

[Experimental validation of the use of the masseter muscle in treating paralysis of the mimetic muscles].

In 15 rabbits the distal end of masseter muscle was surgically transposed to perioral region. After 90, 120 and 180 days the altered muscle position and reduction of functional load did not cause its degeneration. Rather, these conditions elicited a functional reordering evidenced by reduction of muscular fibers' cross-sectional area, the number of surrounding capillaries, decrease in the succinate dehydrogenase activity and increase in connective tissue layer.

Animals↗
PubMed1988

[Experimental validation of a method for the early diagnosis of the infection of vascular prostheses using 99m-TC-labelled leukocytes].

Experiments on 9 dogs were staged for a study of a method of early diagnosis of infectivity of vascular prostheses of the abdominal aorta with the help of 99m-Tc-labelled leukocytes. A sterile synthetic vascular prosthesis was used for prosthetics of the abdominal aorta in the 1st control group of animals, a prosthesis, previously infected with St. aureus, was used in the 2nd group, a sterile prosthesis with its subsequent infecting by i.v. injection of St. aureus was used in the 3rd group. The role of antibiotic therapy in infectivity of vascular prostheses was studied on the animals of the 3rd group. A radionuclide study with autologous 99m-Tc-labelled leukocytes was conducted using the Deina-2 camera (Picker). Visualization of the prostheses was unobserved in the 1st control group; in the 2nd group the accumulation of 99m-Tc-leukocytes in the zone of the prosthesis and its visualization on the 4th-5th min. were noted; in the 3rd group the prosthesis was visualized on the 10th-15th min. After antibiotic therapy in the 3rd group visualization of the prosthesis was undetectable. The proposed method permitted visualization of a zone of infection in the early postoperative period, observation of the time course of infection development, and assessment of the efficacy of antibiotic therapy.

Animals↗