Biomedical subjects

M Peleg

Publications and source records attributed to M Peleg.

At least 19 recordsLinked to original sources

PubMed2003

A model of microbial survival curves in water treated with a volatile disinfectant.

AIM: To develop a method to calculate microbial survival parameters in water treated with a dissipating disinfectant and predict the inactivation patterns under different agent concentrations and decay rate regimes. METHODS AND RESULTS: It has been assumed that the survival curves of the organism, under (hypothetical) constant agent concentration conditions, follow the power law model log [N(t)/N0] = -btn with a concentration independent exponent, n. The concentration dependence of the 'rate parameter', b, has been assumed to obey a log logistic relationship. Under changing disinfectant concentration, the survival curve is constructed so that its local slope, i.e. momentary logarithmic inactivation rate of the organism, is the slope of the momentary 'constant concentration' curve at the momentary agent concentration, at the time which corresponds to the momentary survival ratio. The resulting differential equation was used to retrieve the survival parameters by numerical minimization procedures. Once these are calculated, the equation is solved numerically to produce the survival curve for almost any conceivable agent concentration history. The predictive ability of the method is demonstrated by using the survival parameters, calculated from published data obtained under one concentration profile, to predict survival curves under very different decay patterns. CONCLUSIONS: It is possible to calculate microbial survival parameters from data obtained in treatments where the unstable or volatile disinfectant progressively dissipates and use them to predict the outcome of different treatments. SIGNIFICANCE AND IMPACT OF THE STUDY: The proposed mathematical method will enable the prediction of microbial inactivation patterns in water treated with unstable and/or volatile chemical agents.

Bacteria↗

PubMed2002

Analysis of the process of encoding guidelines: a comparison of GLIF2 and GLIF3.

OBJECTIVES: This study aims to evaluate the use of a modified version of the Guideline Interchange Format (GLIF), GLIF3, in the translation of clinical practice guidelines into an electronically encoded form such that they may be shared among various clinical institutions and settings. METHODS: Based on theories and methods from cognitive science, the encoding of two clinical practice guidelines into two guideline modeling methods (GLIF3 and an earlier version, GLIF2) by two medical informaticians was captured on video and transcribed and annotated for analysis. RESULTS: Differing in both content and structure, the representations developed in GLIF3 were found to contain a greater level of representational detail and less ambiguity than those developed in GLIF2. CONCLUSIONS: The use of GLIF3 in the encoding of clinical guidelines offers significant improvements due to its greater formality as compared to earlier versions of GLIF.

Decision Support Systems, Clinical↗

PubMed2001

Pretreatment prevalence of hypothyroidism in patients with head and neck carcinoma.

BACKGROUND: Hypothyroidism in the normal population age > 60 years is encountered in the range of 0.5-5% clinically, and 5-20% have subclinical hypofunction. Hypothyroidism is recognized as a common complication of treatment in patients with head and neck carcinoma (HNC) and is reported in up to 75% of patients who receive combined treatment. Surprisingly, base-line pretreatment measurements of thyroid function in large series of patients have not been reported. METHODS: Serum thyroid-stimulating hormone, free T4, and total T3 levels were recorded in 110 patients with nonthyroid HNC prior to treatment in a prospective, controlled study. RESULTS: The mean patient age (+/- standard deviation) was 65 years +/- 13.8 years, and 82% of patients had squamous cell carcinoma. A diagnosis of hypothyroidism already was established in 4.5% of patients, and subclinical hypothyroidism was discovered in an additional 6.4% of patients. Sixteen patients had other equivocal anomalies in thyroid function and were referred for further endocrine evaluation. No patients with formerly unrecognized clinical hypothyroidism were found. CONCLUSIONS: Hypothyroidism in patients with head and neck carcinoma in Israel corresponds with the reported incidence in the general population. Hypothyroidism after treatment for head and neck carcinoma stems from the effects of treatment. The need for pretreatment evaluation of thyroid function should be considered.

Adult↗

PubMed2001

A model of microbial contamination of a water reservoir.

A three year record of daily fecal coliform counts in a Massachusetts water reservoir has the appearance of an irregular time series punctuated by outbursts of varying duration. The pattern is described in terms of a probabilistic model where the fluctuations in the 'regular' and 'explosive' regimes are governed by two sets of probabilities. It has been assumed that the random oscillations has a lognormal distribution, and that once an explosion threshold has been exceeded the increments or decrements in the population size have fixed probability distributions. The threshold for triggering an outburst was estimated by examining the randomness of the autocorrelation function of the record after it is filtered to eliminate peaks of progressively increasing magnitude. Once the threshold has been identified, the mean and standard deviation of the underlying lognormal distribution could be estimated directly from remains found in the record after all the peaks were removed. The probabilities of an increment and decrement during the outbursts and their relative magnitudes could also be estimated using simple formulas. These estimated parameter values were then used to generate realistic records with known threshold levels, which were subsequently used to assess the procedure's feasibility and sensitivity.

Computer Simulation↗

PubMed2001

Sharable representation of clinical guidelines in GLIF: relationship to the Arden Syntax.

Clinical guidelines are intended to improve the quality and cost effectiveness of patient care. Integration of guidelines into electronic medical records and order-entry systems, in a way that enables delivery of patient-specific advice at the point of care, is likely to encourage guidelines acceptance and effectiveness. Among the methodologies for modeling guidelines and medical decision rules, the Arden Syntax for Medical Logic Modules and the GuideLine Interchange Format version 3 (GLIF3) emphasize the importance of sharing encoded logic across different medical institutions and implementation platforms. These two methodologies have similarities and differences; in this paper we clarify their roles. Both methods can be used to support sharing of medical knowledge, but they do so in complementary situations. The Arden Syntax is suitable for representing individual decision rules in self-contained units called Medical Logic Modules (MLMs), which are usually implemented as event-driven alerts or reminders. In contrast, GLIF3 is designed for encoding complex multistep guidelines that unfold over time. As a consequence, GLIF3 has several mechanisms for complexity management and additional constructs that may require overhead unnecessary for expressing simple alerts and reminders. Unlike the Arden Syntax, GLIF3 encourages a top-down process of guideline modeling consisting of three levels that are created in order: Level 1 comprises a human-readable flowchart of clinical decisions and actions. Level 2 comprises a computable specification that can be verified for logical consistency and completeness; and Level 3 comprises an implementable specification that includes information required for local adaptation of guideline logic as well as for mapping guideline variables onto institutional medical records. A major emphasis of the current GLIF3 development process has been to create the computable specification that formally represents medical decision and eligibility criteria. We based GLIF3's formal expression language on the Arden Syntax's logic grammar, making the necessary extensions to the Arden Syntax's data structures and operators to support GLIF3's object-oriented data model. We discuss why the process of generating a set of MLMs from a GLIF-encoded guideline cannot be automated, why it can result in information loss, and why simple medical rules are best represented as individual MLMs. We thus show that the Arden Syntax and GLIF3 play complementary roles in representing medical knowledge for clinical decision support.

Computer Simulation↗

PubMed2001

Toward a representation format for sharable clinical guidelines.

Clinical guidelines are being developed for the purpose of reducing medical errors and unjustified variations in medical practice, and for basing medical practice on evidence. Encoding guidelines in a computer-interpretable format and integrating them with the electronic medical record can enable delivery of patient-specific recommendations when and where needed. Since great effort must be expended in developing high-quality guidelines, and in making them computer-interpretable, it is highly desirable to be able to share computer-interpretable guidelines (CIGs) among institutions. Adoption of a common format for representing CIGs is one approach to sharing. Factors that need to be considered in creating a format for sharable CIGs include (i) the scope of guidelines and their intended applications, (ii) the method of delivery of the recommendations, and (iii) the environment, consisting of the practice setting and the information system in which the guidelines will be applied. Several investigators have proposed solutions that improve the sharability of CIGs and, more generally, of medical knowledge. These approaches can be useful in the development of a format for sharable CIGs. Challenges in sharing CIGs also include the need to extend the traditional framework for disseminating guidelines to enable them to be integrated into practice. These extensions include processes for (i) local adaptation of recommendations encoded in shared generic guidelines and (ii) integration of guidelines into the institutional information systems.

Computer Simulation↗

PubMed2001

Patient compliance to instructions after oral surgical procedures.

The purpose of this study was to evaluate patient compliance to postoperative instructions from the oral surgeon. A total of 180 patients who underwent minor oral surgical procedures anonymously answered a questionnaire 1 week postsurgery. This questionnaire was used to evaluate how patients remembered the mode of transmission of instructions (written, verbal), their compliance to the postoperative instructions and to the antibiotic treatment and their comments. Of the patients, 40% did not remember receiving both written and verbal instructions, 36% remembered only the written instructions. Twelve percent did not comply with the postoperative instructions regarding mouthwashes and 67% did not comply with the antibiotic prescriptions; 43% took more antibiotics and 31% less, and 4% who did not receive an antibiotic prescription took them on their own initiative. The academic level of the patients did not influence patient compliance. Verbal and written recommendations worded simply with details are important for patient compliance and reduced postoperative stress and complaints. Better instructions on antibiotics use are necessary to ameliorate patient compliance to the antibiotic treatment.

Adolescent↗

PubMed2001

Upper jugular lymph nodes (submuscular recess) in non-squamous-cell cancer of the head and neck: surgical considerations.

Cervical lymphadenectomy of level II encompasses lymph nodes associated with the upper internal jugular vein and the spinal accessory nerve (SAN). Removal of tissue superior to the SAN (submuscular recess-(SMR)) was recently shown to be unwarranted in selected cases of squamous-cell cancer. Thirty-five patients with non-squamous-cell cancer (SCC) of the head and neck treated with cervical lymphadenectomy were prospectively evaluated. Thirty-seven neck dissection specimens were histologically analysed for the number of lymph nodes involved with cancer. At the time of surgery, level II was separated into the supraspinal accessory nerve component (IIa) and the component anterior to the SAN (IIb). Neck dissections were most commonly performed for cancer of the thyroid gland (19) followed in frequency by the parotid gland (seven), skin: melanoma (five), basal-cell cancer (two), and other sites (four). Twenty-five neck dissections were modified-selective procedures and 12 were either radical or modified radical neck dissection. Twenty-nine necks were clinically N+ and eight N0. Histological staging was pathologically N+ in 32 neck dissection specimens. Level IIb contained an average of 12 nodes and the IIa component contained a mean of 5.0 nodes. Level II contained metastatic disease in 28 of 32 histologically node-positive specimens (87 per cent). Level IIa was involved with cancer in six cases (16 per cent), five of which were pre-operatively staged as clinically N+. All cases (100 per cent) with level IIa involvement had level IIb positive nodes. Three of the level IIa positive cases were cancer of the parotid gland comprising 43 per cent of this sub-group of patients. Incidence of involvement of SMR in non-SCC cases is not uncommon. The additional time required and morbidity associated with dissection of the supraspinal accessory nerve component of level II are probably justified when performing neck dissection in cancer of the thyroid gland. The SMR should be excised in cancer of the parotid gland. Large-scale prospective controlled studies with long-term follow-up periods are necessary to support resection of level IIb only.

Adolescent↗

PubMed2001

Calculating Salmonella inactivation in nonisothermal heat treatments from isothermal nonlinear survival curves.

Salmonella cells in two sugar-rich media were heat treated at various constant temperatures in the range of 55 to 80 degrees C and their survival ratios determined at various time intervals. The resulting nonlinear semilogarithmic survival curves are described by the model log10S(t) = -b(T)tn(T), where S(t) is the momentary survival ratio N(t)/N0, and b(T) and n(T) are coefficients whose temperature dependence is described by two empirical mathematical models. When the temperature profile, T(t), of a nonisothermal heat treatment can also be expressed algebraically, b(T) and n(T) can be transformed into a function of time, i.e., b[T(t)] and n[T(t)]. If the momentary inactivation rate primarily depends on the momentary temperature and survival ratio, then the survival curve under nonisothermal conditions can be constructed by solving a differential equation, previously suggested by Peleg and Penchina, whose coefficients are expressions that contain the corresponding b[T(t)] and n[T(t)] terms. The applicability of the model and its underlying assumptions was tested with a series of eight experiments in which the Salmonella cells, in the same media, were heated at various rates to selected temperatures in the range of 65 to 80 degres C and then cooled. In all the experiments, there was an agreement between the predicted and observed survival curves. This suggests that, at least in the case of Salmonella in the tested media, survival during nonisothermal inactivation can be estimated without assuming any mortality kinetics.

Animals↗

PubMed2001

Estimating the frequency of high microbial counts in commercial food products using various distribution functions.

Industrial microbial count records usually form an irregular fluctuating time series. If the series is truly random or weakly autocorrelated, the fluctuations can be considered as the outcome of the interplay of numerous factors that promote or inhibit growth. These factors usually balance each other, although not perfectly, hence, the random fluctuations. If conditions are unchanged, then at least in principle the probability that they will produce a coherent effect, i.e., an unusually high (or low) count of a given magnitude, can be calculated from the count distribution. This theory was tested with miscellaneous industrial records (e.g., standard plate count, coliforms, yeasts) of various food products, including a dairy-based snack, frozen foods, and raw milk, using the normal, log normal, Laplace, log Laplace, Weibull, extreme value, beta, and log beta distribution functions. Comparing predicted frequencies of counts exceeding selected levels with those actually observed in fresh data assessed their efficacy. No single distribution was found to be inherently or consistently superior. It is, therefore, suggested that, when the probability of an excessive count is estimated, several distribution functions be used simultaneously and a conservative value be used as the measure of the risk.

Colony Count, Microbial↗

PubMed2001

Sharable computer-based clinical practice guidelines: rationale, obstacles, approaches, and prospects.

Clinical practice guideline automation at the point of care is of growing interest, yet most guidelines are authored in unstructured narrative form. Computer-based execution depends on a formal structured representation, and also faces a number of other challenges at all stages of the guideline lifecycle: modeling, authoring, dissemination, implementation, and update. This is because of the multiplicity of conceptual models, authoring tools, authoring approaches, intended applications, implementation platforms, and local interface requirements and operational constraints. Complexity and time required for development and structure are also huge obstacles. These factors argue for convergence on a common shared model for representation that can be the basis of dissemination. A common model would facilitate direct interpretation or mapping to multiple implementation environments. GLIF (GuideLine Interchange Format) is a formal representation model for guidelines, created by the InterMed Collaboratory as a proposed basis for a shared representation. GLIF currently addresses the process of authoring and dissemination; the InterMed team's major focus now is on tools to facilitate these tasks and the mapping to clinical information system environments. Because of limitations in what can be done by a single team with finite resources, however, and the variety of additional perspectives that need to be accommodated, the InterMed team has determined that further development of a shared representation would be best served as an open process in which the world community is engaged. Under the auspices of the HL7 Decision Support Technical Committee, a GLIF Special Interest Group has been established, which is intended to be a forum for collaborative refinement and extension of a standard representation that can support the needs of the guideline lifecycle. Significant areas for future work will need to include demonstrations of effective means for incorporating guide-lines at point of care, reconciliation of functional requirements of different models and identification of those most important for supporting practical implementation, im-proved means for authoring and management of complexity, and methods for automatically analyzing and validating syntax, semantics, and logical consistency of guidelines.

Artificial Intelligence↗

PubMed2001

Handling expressiveness and comprehensibility requirements in GLIF3.

Clinical guidelines are aimed at standardizing patient care and improving its quality and cost effectiveness. Guidelines represented in a computer-interpretable (CI) format can be used to provide automatic decision support applied to individual patients during the clinical encounter. The process of creating computer-interpretable guidelines (CIG) re-moves ambiguities contained in paper-based guidelines, thus making the guideline more comprehensible. For these reasons, CIGs may have a larger impact on clinician behavior than paper-based guidelines. Since much effort goes into creating guidelines in a CI format, it is desirable that different institutions and software systems share them. In a guideline representation workshop hosted by the InterMed Collaboratory in March 2000, the need for a standard representation format for sharable CIGs was recognized. As a first step towards achieving this goal, we proposed a set of functional requirements for sharable CIGs. The requirements encompass the entire life cycle of a CIG: development, implementation, use and maintenance. In this paper we discuss requirements that are important during the development stage of a CIG. We have abstracted the requirements into two groups: expressiveness--the ability to ex-press the knowledge content of different types of guidelines--and comprehensibility--the ability to manage complexity, facilitate coherence, and visualize a guideline model to aid in human comprehension. The Guideline Interchange For-mat version 3 (GLIF3) is a language for structured representation of CIGs. It is under development to facilitate sharing CIGs among different institutions and systems. We illustrate how GLIF3 meets the specified development requirements.

Decision Making, Computer-Assisted↗

PubMed2001

Representation of clinical practice guidelines for computer-based implementations.

Representation of clinical practice guidelines is a critical issue for computer-based guideline development, implementation and evaluation. We studied eight types of computer-based guideline representation models. Typical primitives for these models include decisions, actions, patient states and execution states. Temporal constraints and nesting are important aspects of guideline structure representation. Integration of guidelines with electronic medical records can be facilitated by the introduction of formal models of patient data. Patient states and execution states are closely related to one another. Data collection, decision, patient state and intervention are four basic steps in a guideline's logic flow.

Artificial Intelligence↗

PubMed2001

Using features of Arden Syntax with object-oriented medical data models for guideline modeling.

Computer-interpretable guidelines (CIGs) can deliver patient-specific decision support at the point of care. CIGs base their recommendations on eligibility and decision criteria that relate medical concepts to patient data. CIG models use expression languages for specifying these criteria, and define models for medical data to which the expressions can refer. In developing version 3 of the GuideLine Interchange Format (GLIF3), we used existing standards as the medical data model and expression language. We investigated the object-oriented HL7 Reference Information Model (RIM) as a default data model. We developed an expression language, called GEL, based on Arden Syntax's logic grammar. Together with other GLIF constructs, GEL reconciles incompatibilities between the data models of Arden Syntax and the HL7 RIM. These incompatibilities include Arden's lack of support for complex data types and time intervals, and the mismatch between Arden's single primary time and multiple time attributes of the HL7 RIM.

Decision Making, Computer-Assisted↗

PubMed2000

On estimating the probability of aperiodic outbursts of microbial populations from their fluctuating counts.

The irregular sequence of counts of a microbial population, in the absence of observable corresponding environmental changes (e.g., temperature), can be regarded as reflecting the interplay of several unknown or random factors that favor or inhibit growth. Since these factors tend to balance one another, the fluctuations usually remain within bounds, and only by a coincidence--when all or most act in unison--does an 'outburst' occur. This situation can be represented mathematically as a sequence of independent random variables governed by a probability distribution. The concept was applied to reported microbial counts of ground meat and wastewater. It is found that the lognormal distribution could serve as a model, and that simulations from this model are indistinguishable from actual records. The parameters of the lognormal (or other) distribution can then be used to estimate the probability of a population outburst, i.e., an increase above a given threshold. Direct estimation of the outburst probability based on frequency of occurrence is also possible, but in some situations requires an impractically large number of observations. We compare the efficiency of these two methods of estimation. Such methods enable translation of irregular records of microbial counts into actual probabilities of an outburst of a given magnitude. Thus, if the environment remains 'stable' or in dynamic equilibrium, the fluctuations should not be regarded merely as noise, but as a source of information and an indicator of potential population outbursts even where obvious signs do not exist.

Animals↗

PubMed2000

Pain in the neck after neck dissection.

BACKGROUND: Reports of disability after neck dissection have been directed toward shoulder dysfunction and pain. We could find no report addressing the issue of pain localized to the actual operative site. We have conducted a combined prospective and retrospective study of pain in patients undergoing neck dissection. METHODS: Eighty-eight disease-free patients were evaluated in 3 groups for neck pain. One group was followed up prospectively for 1 to 8 months after surgery, and 2 retrospective groups were followed up for more than 2 years or for 6 months to 2 years. Pain was assessed by a body map and visual analog scale. RESULTS: None of 31 patients followed up for more than 2 years reported neck pain. Four of 27 patients followed up for 6 to 24 months had pain, with a mean visual analog scale score of 3.7. Seventy percent of the prospective group of 30 patients had pain during the first postoperative week, and only 1 patient had pain persisting for more than 2 months. Shoulder pain and disability after radical neck dissection were encountered in all groups, comparable with the incidence reported in the literature. No postoperative neuromas were found. CONCLUSIONS: Chronic pain localized to the operative site is an uncommon occurrence even after radical neck dissection. Chronic pain in the shoulder region may follow radical neck dissection, whereas modified neck dissection is usually a painless procedure.

Adult↗

PubMed2000

Modeling microbial survival during exposure to a lethal agent with varying intensity.

Traditionally, the efficacy of preservation and disinfection processes has been assessed on the basis of the assumption that microbial mortality follows a first-order kinetic. However, as departures from this assumed kinetics are quite common, various other models, based on higher-order kinetics or population balance, have also been proposed. The database for either type of models is a set of survival curves of the targeted organism or spores determined under constant conditions, that is, constant temperature, chemical agent concentration, etc. Hence, to calculate the outcome of an actual industrial process, where conditions are changing, as in heating and cooling during a thermal treatment or when the agent dissipates as in chlorination or hydrogen peroxide application, one has to integrate the momentary effects of the lethal agent. This involves mathematical models based on assumed mortality kinetics, and simulated or measured history, for example, temperature-time or concentration-time relationships at the "coldest" point. It is shown that the survival curve under conditions where the agent intensity increases, decreases, or oscillates can be constructed without assuming any mortality kinetics and without the use of the traditional D and Z values, which require linear approximation, and without thermal death times, which require extrapolation. The actual survival curves can be compiled from the isothermal survival curves provided that growth and damage repair do not occur over the pertinent time scale and that the mortality rate is a function of only the momentary agent intensity and of the organism's or spore's survival fraction (but not of the rate at which this fraction has been reached). The calculation is greatly facilitated if both the "isothermal" survival curves and the time-dependent agent intensity can be expressed algebraically. The differential equation derived from these considerations can be solved numerically to produce the required survival curve under the changing conditions. The concept is demonstrated with simulated survival curves during heating at different rates, heating and cooling cycles, oscillating temperature, and exposure to a dissipating chemical agent. The simulated thermal processes are based on published data of Clostridium botulinum spores, whose semilogarithmic survival curves have upward concavity and on a hypothetical "Listeria-like" organism whose semilogarithmic curves have downward concavity.

Clostridium botulinum↗

PubMed2000

The use of hydroxyapatite bone cement for sinus floor augmentation with simultaneous implant placement in the atrophic maxilla. A report of 10 cases.

BACKGROUND: Dental implant placement associated with sinus floor augmentation in a severely atrophic maxilla can be performed in a 1- or 2-stage surgical procedure, depending on the height of the residual alveolar bone. A minimum of 4 to 5 mm is recommended for a 1-stage procedure. METHODS: This clinical study describes the use of hydroxyapatite (HA) bone cement to stabilize HA-coated cylindrical implants placed simultaneously during sinus augmentation in 100 patients where insufficient bone volume did not allow primary implant stability. A total of 26 HA-coated dental implants were inserted in 100 grafted sinuses of 10 patients. RESULTS: None of the cases presented any difficulty in achieving initial stabilization and parallelism. No clinical complications of the sinuses were evident. Prior to exposure, radiographic evaluation revealed the implants embedded in a densely homogeneous radiopaque mass. At second-stage surgery, there was no clinical evidence of crestal bone loss around the implants. All implants were clinically osseointegrated. All patients received fixed implant-supported prostheses. Mean follow-up was 18 months (range 12 to 24 months). CONCLUSIONS: According to this preliminary study, the hydroxyapatite bone cement appears to hold great promise as a grafting alloplastic material for sinus floor augmentations. Its main advantage is its ability to provide initial stability required for osseointegration and proper implant location and parallelism. Further clinical and histological studies are required before it can be recommended for routine use in sinus lift procedures.

Adult↗