This simulation is a VAM-like version
of a dialysis machine, specifically a CVVH (Continuous Veno Veno
Hemodialysis) machine. It is modeled after BBraun's Diapact CRRT.
Development was funded entirely by the University of Florida (UF)
in an unsucccessful effort to develop a collaborative educational
simulation in partnership with BBraun. UF is currently seeking
industry partners to continue development of the CVVH/dialysis
simulations. The simulation is targeted primarily towards ICU nurses,
who may need to interface with the dialysis machine
when dialysis technicians are unavailable.
Stochastic Visualization of a One-Compartment PK Model
Knowledge of first-order systems and the characteristics of
exponential functions is necessary to understand basic pharmacokinetics.
This interactive simulation is designed to illustrate the exponential
nature of a first order system to a learner without a background
in mathematics or physics.
Particles move randomly about a table with a hole. The more particles
there are on the table, the more drop through the hole. A plot
of the number of particles remaining on the table is an exponential.
The particles are analogous to drug molecules, the table is
analogous to a compartment, and the hole is analogous to drug clearance
in the circulation.
Plots from two consecutive runs with identical settings will be
slightly different because of the stochastic nature of the simulation,
but it is useful for visualization purposes, especially for the lay
person. A version with two compartments that displays second order
behavior is also available below.
Based on deterministic equations, this simulation of a hydraulic
analog of a single compartment pharmacokinetic model facilitates
visualization of the response to a bolus injection. The height
of the meniscus, the cross-sectional area and the size
of the drain hole are user adjustable and correspond to the
drug concentration, the volume of distribution and the clearance
Stochastic Visualization of a Two-Compartment
This simulation is mainly for visualization purposes and is similar
in design to the first order stochastic visualization described
above. It illustrates the nature of a second order system
without resorting to mathematics.
Particles representing drug molecules move randomly between two areas (depicting two compartments, such as plasma and tissue) through two individually adjustable directional transfer paths (K12 and K21). One area has a hole analogous to drug clearance in the circulation (Kel).
Because of the stochastic nature of the simulation, plots from two
consecutive runs with identical user-adjustable settings will be
slightly different, as opposed to repeatable outputs with a similar
deterministic simulation. The plots driven by the stochastic simulation
display exponential behavior but are rough, especially
when the number of particles is small. Real second-order pharmacokinetic
systems have trillions of particles.
Based on deterministic equations, this simulation of a hydraulic
analog of a two compartment pharmacokinetic model facilitates visualization
of the response to a bolus injection, infusion and oral administration.
The drug concentration in both compartments is plotted.
In this simulation, the ventilator drive gas may
be configured to come from either the oxygen or air manifold;
an Aeetiva or Modulus II high pressure system is user-selectable
and allows users to appreciate the subtle differences between
the 2 designs such as different oxygen failsafe
valves and cylinder pressure gauge behaviors when the cylinders
are removed. Cylinders may be disconnected and drained to see
how the systems respond to inadequate pressures. The operation
of the ball-in-tube auxiliary O2 flowmeter is simulated.
This simulation may be configured to reflect different anesthesia
machine designs. Options include an air flowmeter, a second vaporizer,
a common gas outlet, a common gas outlet checkvalve, and a selectable
auxiliary common gas outlet.
There is a wide variation in scavenging systems around the world.
This simulation models the active open (common in Europe), active
bag (common in US), passive bag, and the passive activated charcoal
scavenging systems. All simulations may be configured to scavenge
ventilator drive gas.
The unique features of Instructor VAM relative to the free basic VAM
version are listed below.
Fourteen anesthesia machine faults and a randomized mystery fault.
A tutorial on how to use instructor VAM and how the faults may be used
Ability to pause/resume the simulation
Ability to hide/show the gas molecule icons, depending on teaching
style or to make some faults less obvious
Ability to select and track a single gas molecule as it flows through
Adjustable Ventilator Settings
Inspiratory pressure limit
SpO2 including tones and alarms
FiO2 including alarm
Capnogram including normal and abnormal capnograms
Airway pressure trace
Exhaled VT measurement
Minute ventilation measurement
Audible alarm and silence button
How to Obtain Access to the VAM
To obtain free access to the VAM instructor area, ask representatives
of drug and anesthesia equipment companies to sponsor
access to the VAM instructor area (US$100 per year
per instructor). Alternatively, you or your hospital, University or
institution can purchase access
to the VAM Instructor area by sending US$100 by credit card or check/money
order for an annual fee. Click here for
details for sponsoring/obtaining access to the VAM instructor area.
Continued free access to the simulations in the free Member's Area
is supported, in part, by the fees for accessing the VAM Instructor
Why is the Access Model Being
Tweaked for the VAM Instructor Area?
The VAM project, beyond being an exploration of model-driven, interactive
web simulation, is also an experiment in sustainable web philanthropy.
The VAM team, with the financial support of the chair of the UF Department
of Anesthesiology, made the decision right from the start in 1999
to make the VAM simulation available free of charge over the Web so
that financial means would not be a barrier to access to essential
patient safety materials. Our strategy was to obtain funding via corporate
sponsorship and donations to eventually (within 5 years) meet the VAM
team's payroll and make the VAM project self-sustaining.
Five years into this funding experiment, we had to
admit that VAM's philanthropic access model as originally conceived
has failed and will not work without tweaking. From 1999 to 2004,
we received $22,500 in corporate sponsorship and $510 in donations,
accounting for less than 5% of the total VAM team payroll.Lampotang
et al, Anesthesiology
99: A1319, 2003
It is important to note that the simulations in the Member's
Area remain free. Access to the VAM instructor area is also
"free" to you if one of your industry contacts sponsors you.