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ARCHIVE ADDITIONS Abstract

The APS archive of teaching resources (http://www.apsarchive.org) is a repository of case histories, simulations, figures, lectures and course syllabi, animations, and links to physiology teaching resources for use by APS members and other educators. The Archive is a searchable database that can be used by teachers at all levels (K-12, undergraduate, graduate, and medical school) to enhance and supplement their current teaching resources and is part of the National Science Digital Library Project (http://www.nsdl.org) and the BiosciEd Net collaborative (http://www.biosciednet.org). The APS Archive of Teaching Resources was established as an initiative of the APS Education Committee and APS Council with additional support from the National Science Foundation (DUE 0226185). Authors submitting materials to the Archive for review and inclusion have the option of developing an abstract for publication in Advances in Physiology Education. The following abstracts are from items that have been accepted into the Archive following peer review.

Capillary Pressure (Learning Objects #890 and #1012)

A. Shepherd, Ph.D., Department of Physiology, University of Texas Health Science Center, San Antonio, TX 78229

Capillary Pressure is a computer program (Mac and Windows versions, respectively) that illustrates, in quantitative terms, the vascular control of capillary hydrostatic pressure (Pc). The program can be used for classroom simulations or as a self-instructional device. Help screens describe suggested simulations students can run. Variables that can be manipulated include arterial and venous resistances and pressures. The simulations are useful for upper-level undergraduate students, graduate students, and professional degree program students.

Cardiovascular Interactions: A Major Revision of Mating an Interactive Lab Book and a Mathematical Model (Learning Objects #973, #995, #996, and #997)

Carl F. Rothe, Ph.D., Department of Cellular and Integrative Physiology, Indiana University School of Medicine, Indianapolis, IN 46202

What if? and Why? What is the cardiovascular response to a change of a defining parameter of the heart or vasculature? Why did various cardiovascular variables change? Understanding the answers to these questions is the goal of the Cardiovascular Interactions Project (CVI Project).

The CVI Project is an interactive learning tool that demonstrates the complex and intricate interactions between the functions of the heart and peripheral circulation to provide an adequate cardiac output during various stresses. The original description of the CVI Project and software were published in Advances in Physiology Education in 2002 (http://advan.physiology.org/cgi/content/full/26/2/98/DC1).

This extensive revision (version 5) provides a more accurate, effective, and user-friendly learning and teaching application than the earlier edition published in 2002. The six-compartment mathematical model now includes a pulmonary venous bed. Separate control of right and left ventricular heart rates permits the study of arrhythmias.

The mathematical Model reflects our current understanding of the basic function of the cardiovascular system. It is complex enough to be realistic, yet not so complex as to be overwhelming. The model has six compartments to represent the major parts of the cardiovascular system-a left ventricle, systemic arterial bed, systemic venous bed, right ventricle, pulmonary arterial bed, and pulmonary venous bed. The model includes 18 defining and changeable parameters and 34 variables.

Model basic relationships:

1. Compliance and the stressed volume determine the distending pressure.
   
2. Resistance and the outflow pressure gradient determine the flow.
   
3. Conservation of mass (mass balance principle), computed as the integral of the difference between inflow and outflow of a compartment, determines the change in its stressed volume at each iteration. (The difference-differential equations are solved iteratively at 0.001-min intervals.)
   
4. Vigor of cardiac contraction.
   1. The magnitude of preload, which is the end-diastolic volume, is the basis of the Frank-Starling Law of the Heart) and
      
   2. The magnitude of afterload is the end-systolic pressure. The end-systolic pressure, in conjunction with the end-systolic elastance (E_es or E_max), determines the end-systolic volume. The end-systolic pressure, which occurs when cardiac ejection stops, is assumed to equal to the mean arterial pressure.
      
   
   
5. Cardiac output is computed as heart rate times (end-diastolic volume minus end-systoic volume) at each iteration.
   

Implementation of the mass balance principle is the key to the utility and reliability of the model. With the use of this principle, volume is redistributed between the six compartments in accordance with the set of equations and current parameter set. The model demonstrates the concept that mechanical feedback mechanisms (such as passive blood volume redistribution influencing ventricular preload and afterload) controls the cardiovascular system to reduce its susceptibility to disturbances that could cause derivations from optimal function-homeostasis.

The Lab Book is an interactive tutorial for exploring the relative influences of parameter changes on the cardiovascular system, such as changes in vascular compartment resistance to outflow, compartment compliance, ventricular contractility [via end-systolic elastance (E_ES or E_MAX)], heart rate, intrathoracic pressure, unstressed vascular volume, or blood volume. Simulation "experiments" explore the consequences of heart failure (and compensation by volume retention), hemorrhage, exercise, excessive changes in heart rate, arrhythmia, or intrathoracic pressure. The revised version now includes a pulmonary venous bed with its own compliance, outflow resistance, and stressed volume. We assume that that the pulmonary venous pressure is closely similar to the pulmonary capillary pressure. The observer is warned if pulmonary edema is likely to occur during stressful situations. The interactive Lab Book assists the user to understand the physiology of the circulatory system by emphasizing the basic relationships of causes and effects involved with function.

The "experimental results" displayed in the Lab Book come from the mathematical model via hypertext "Get" tags. Parameter changes in the Lab Book are transmitted to the model via "Put" tags. Topics, which may be unfamiliar to the user, are displayed in blue underlined font for hypertext jumps to the Information file. Using the Lab Book, 17 major experiments are available for study that is based on predictions requested and questions asked. In the Information file, discussion of each experiment demonstrates the chain of causes and effects related to the parameter change or stress induced.

A Data Plot screen displays (iteration by iteration) the mean systolic blood pressure, cardiac output, and venous return. This display is helpful in understanding the pattern of the changes. Beat-by-beat patterns of pressure and flow are not computed because they are not needed and would greatly complicate the computations.

An Information File contains definitions and descriptions of key classical physiology concepts, including figures, and a discussion of the Lab Book "experiments." It also includes a detailed description of the model, documentation of parameter values use, and instructions for use of the CVI Project. An Index provides ready access to the contents of this file. Both the Information and the Lab Book have a detailed Table of Contents.

Learners Targeted. This project will improve the understanding of the cardiovascular system at the total body level for teachers, professors, clinicians, and scientists as well as medical, graduate, and bioengineering students who need a clear and consistent grasp of its complexities.

Availability

The 2005 version of the CVI Project is available from the APS Archive of Teaching Resources. There are four files:

1. CVI Instructions: for downloading and running the CVI Project.
   
2. CVI Project.exe: the application that is downloaded as a 3-MB self-extracting file and then expanded to 6.5- and 37-MB files. Double clicking the CVI.exe file starts the program.
   
3. CVI Model.exe: an *.avi, audio-video file that uses the mathematical model to demonstrate the consequence of a reduction in left ventricular diastolic compliance. It is downloaded as a 3.7-MB self-extracting file and runs for 12 min.
   
4. CVI Lab Book.exe: an *.avi, audio-video file that uses the model and Lab Book to demonstrates and record the consequences of left ventricular failure. It is downloaded as a 3.3-MB self-extracting file and runs for 9.4 min.
   

Contact crothe{at}iupui.edu for a copy of the CVI Project on a compact disk (CD).

Pathophysiology and Treatment of Sarin (Anti-Cholinesterase) Poisoning (Learning Object #980)

Beth A. Habecker, Ph.D., Department of Physiology and Pharmacology, Oregon Health and Science University School of Medicine, Portland, OR 97239

This multimedia movie uses first-hand accounts from Japanese physicians and victims of the Tokyo subway sarin attack to describe the symptoms and treatment of anti-cholinesterase poisoning. Visual overlays of the symptoms and treatment are combined with pictures from the attacks and a voice over from personal accounts. This movie has been successful in communicating the major aspects of anti-cholinesterase pharmacology and treatment to first-year medical students. A study guide is also available that covers background information on cholinergic neurotransmission, anti-cholinesterases, and the relative susceptibility to muscarinic versus nicotinic effects. Personal stories are taken from the book Underground by Haruki Murakami. The author has granted permission for this copyrighted material to be used for educational purposes through November 5, 2007. Generated in Flash, this is a very large (300 MB) *.avi file that can be viewed using free versions of Windows Media player or RealPlayer. Because of the large file size and long download time, CD versions can be obtained from author upon request.

This article has been cited by other articles:

				C. F. Rothe Commentary on Viewpoint "Human experimentation: No accurate, quantitative data?" J Appl Physiol, March 1, 2007; 102(3): 1289 - 1289. [Full Text] [PDF]

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