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Biomedical subjects

E D Lehmann

Publications and source records attributed to E D Lehmann.

At least 37 records · Page 2Linked to original sources
PubMed1999

Experience with the Internet release of AIDA v4.0--http://www.diabetic.org.uk.aida.htm--an interactive educational diabetes simulator.

AIDA v4.0 is a freeware computer program that permits the interactive simulation of plasma insulin and blood glucose profiles for demonstration and teaching purposes. It has been made freely available, without charge, on the World Wide Web as a noncommercial contribution to continuing diabetes education. Since its Internet launch in 1996 over 23,000 people have visited the AIDA Web site (http://www.diabetic.org.uk/aida.htm) and over 7,750 copies of the program have been downloaded gratis. This report overviews the Internet release of AIDA v4.0 and provides examples of the simulator in operation. The concept of a "virtual diabetic patient" is introduced. This provides an electronic representation of a patient with diabetes that can be used for self-learning/teaching/demonstration purposes.

Computer Simulation↗
PubMed1999

Terminology for the definition of arterial elastic properties.

A profusion of terminology for the description of arterial elastic properties can be found in the literature. This can cause confusion and make comparisons between studies and between different research groups problematical. The multitude of definitions--including "lay" terms--for indices like "compliance" and "distensibility" is highlighted, and it is proposed that a rapidly expanding field such as that studying arterial biophysical properties in vivo will not receive the respect it deserves if fundamental terms can have a multitude of different definitions, absolute values and units. It is also demonstrated that the beta stiffness index, quite widely quoted as a blood pressure corrected index, does nevertheless exhibit considerable blood pressure dependence--especially in patients with cardiovascular risk factors and/or disease. It is questioned whether all of the 24 indices identified for this review really are needed. Furthermore it is suggested that while a number of the parameters may provide complimentary information--depending on which aspects of the vasculature are to be described--there is a very real need for some form of consensus or agreement about terminology for the definition of arterial biophysical properties.

Arteries↗
PubMed1999

Noninvasive measurements of aortic stiffness: methodological considerations.

This article overviews methods currently available for the non-invasive determination of aortic stiffness and critically appraises their strengths and weaknesses. Approaches are divided into indirect and direct (Windkessel models are not reviewed). Indirect techniques rely on the measurement of pulse wave velocity (PWV) to obtain information about the average stiffness of the vessel pathway being studied. Typically "foot-to-foot" transit time measurements are combined with transcutaneous length measurements to calculate PWV (as length/transit time). Applanation tonometry, acoustic transducers, Doppler ultrasound and magnetic resonance imaging (MRI) have all been used to measure transit times. Direct techniques rely on assessing the relative change in aortic diameter (or area) between systole and diastole (strain) and combine these data with pulse pressure (stress) measurements to calculate vessel stiffness (as stress/strain). Transthoracic echocardiography and MRI have been used to assess aortic strain. All the approaches--both direct and indirect--however have their limitations. For indirect techniques the greatest errors are likely to be introduced by the transcutaneous estimation of the aortic path length. For direct techniques stress and strain are generally measured in different portions of the vasculature. These and other methodological issues are considered and areas where further work is needed are highlighted.

Aorta↗
PubMed1999

Interactive educational diabetes simulators: future possibilities.

In 1996 an interactive educational diabetes simulator called AIDA was released without charge on the Internet as a non-commercial contribution to continuing diabetes education. Over the past 3 years over 30,000 people have visited the AIDA Web site-- http://www.diabetic.org.uk/aida.htm--and over 10,000 copies of the program have been downloaded from there free-of-charge. This review builds on the experience gained from the AIDA development and the World Wide Web distribution of the software, and looks to the future, highlighting features which users might expect to see in future generations of such interactive educational diabetes programs. Novel functions already described in the literature are overviewed, and possible applications using personal computers and the Internet are discussed. The importance of the user interface is stressed. The concept of a "virtual diabetic patient" that provides an electronic representation of a patient with diabetes--and which can be used for self-learning/teaching/demonstration purposes--is highlighted.

Blood Glucose↗
PubMed1998

Preliminary experience with the Internet release of AIDA--an interactive educational diabetes simulator.

This paper overviews the Internet release of AIDA, a freeware interactive educational diabetes simulator. Since its release on the World Wide Web as a non-commercial contribution to continuing diabetes education over 14,000 people have visited the AIDA Web site--http:/(/)www.diabetic.org.uk/aida.htm--and over 5000 copies of the program have been downloaded, without charge. User responses thus far have been very encouraging. Example feedback and clinical experience reported by two insulin-dependent (type 1) diabetic patients, a patient's carer, the father of a diabetic teenager, a diabetes doctor and nurse educator, an endocrinologist and a postgraduate educator are presented. While such anecdotal, qualitative assessments are worthwhile and form a necessary step in the overall evaluation process--they are clearly subjective in nature and fully recognised as such. Given this, definitive outcome measures are highlighted as being required for the next stage in the evaluation process, and various objective evaluation criteria are proposed. A general protocol for the evaluation of interactive educational simulation tools, like AIDA, with patients is described and the concept of applying this in multiple centres--as a way of increasing study sample sizes--is discussed. It is highlighted that such a protocol could also be used to objectively compare a number of different interactive educational diabetes simulators. Clinicians who are interested in collaborating by enrolling patients into such a study are invited to contact the author, by email, at aida@globalnet.co.uk

Computer Simulation↗
PubMed1998

Compartmental models for glycaemic prediction and decision-support in clinical diabetes care: promise and reality.

This paper reviews and critically appraises the application of compartmental models for generating glycaemic predictions and offering clinical decision support in diabetes care. Comparisons are made with alternative algorithmic-based approaches. Unresolved issues raised for model-based techniques include the relative lack of input data necessary for generating reasonable blood glucose predictions, and the high level of uncertainty associated with such predictions which limits their use as guides for therapeutic insulin-dosage adjustments. It is concluded that compartmental model-based approaches, while not offering much benefit for clinical/therapeutic application, will have a role to play as research tools and for educational use. By contrast it is proposed that algorithmic-based approaches, especially in conjunction with telemedicine and Internet applications, are likely to see growing use for day-to-day therapeutic decision support. Randomised controlled clinical trials however will be required, together with other evaluation efforts, before algorithmic-based approaches-like any other clinical technique-can be widely adopted into routine medical practice.

Algorithms↗
PubMed1998

Relation between number of cardiovascular risk factors/events and noninvasive Doppler ultrasound assessments of aortic compliance.

The aim of this study was to establish the relation between noninvasive Doppler ultrasound assessments of aortic compliance, based on "foot-to-foot" aortic pulse wave velocity measurements, and presumed atherosclerotic load in patients with vascular disease and/or diabetes mellitus. One hundred ten patients with vascular disease and/or diabetes mellitus (arteriopaths) underwent measurement of in vivo aortic compliance using Doppler ultrasound. Demographic data on these subjects were recorded along with details of cardiovascular risk factors and events. Aortic compliance values were compared with data from 51 age-matched healthy, asymptomatic subjects putatively free of vascular disease (controls). Data are expressed as mean+/-SD. Arteriopaths were aged 64.1+/-8.4 years and had total cholesterol levels of 5.9+/-1.1 mmol/L and aortic compliance of 0.78+/-0.42%/10 mm Hg [1.33 kPa]. Most arteriopaths had 2 or more cardiovascular risk factors and events: diabetes (n=41), hypertension (n=45), smoking (n=86), cerebrovascular/transient ischemic event (n=13), myocardial infarction (n=44), angina (n=51), and/or peripheral vascular disease (n=33). Controls were aged 64.3+/-12.1 years with total cholesterol of 6.1+/-1.1 mmol/L and aortic compliance of 1.14+/-0.46%/10 mm Hg [1.33 kPa] (P<0.002 versus arteriopaths). Subset analysis revealed that patients with the greatest number of cardiovascular risk factors and events (n=5) had the stiffest aortas (aortic compliance, 0.58+/-0.15%/10 mm Hg [1.33 kPa]) compared with those patients with the median and mean (n=2) number of risk factors and events (aortic compliance, 0.80+/-0.50%/10 mm Hg [1.33 kPa]; P<0.02). The data suggest that a significant inverse relation exists between presumed atherosclerotic load (as assessed by the number of cardiovascular risk factors and events) and aortic compliance determined noninvasively based on aortic pulse wave velocity measurements. If these findings are confirmed by prospective, longitudinal follow-up studies, such measurements may prove useful as a noninvasive marker of vascular risk.

Adult↗