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Transcript of Gas Man ® Understanding Inhalation Kinetics Through Computer Simulation © Copyright 1980 - 2005,...
Gas Man® Understanding Inhalation Kinetics
Through Computer Simulation
© Copyright 1980 - 2005, James H Philip, all rights reserved
Ready
Gas Man® Understanding Inhalation Kinetics
Through Computer SimulationJames H. Philip, M.E.(E.), M.D.
Anesthesiologist andDirector of Anesthesia Technology,
Brigham and Women's HospitalAssociate Professor of Anaesthesia,
Harvard Medical SchoolMedical Liaison, Partners Biomedical EngineeringPresident, Society for Technology in Anesthesia
Everything profitable I ever invented is owned by Brigham and Woman’s Hospital(Edwards Vigilance CCO, Baxter-Bard InfusOR Pump, IVAC-Alaris Signature Pump
Perkin-Elmer Life Watch™ CO2 Monitor)
Gas Man® Understanding Inhalation Kinetics
Through Computer SimulationJames H. Philip, M.E.(E.), M.D.
Anesthesiologist andDirector of Anesthesia Technology,
Brigham and Women's HospitalAssociate Professor of Anaesthesia,
Harvard Medical SchoolMedical Liaison, Partners Biomedical EngineeringPresident, Society for Technology in Anesthesia
I have performed funded research on Sevoflurane, Desflurane, IsofluraneI have a financial interest in Gas Man® and Med Man Simulations, Inc.
UVM owns a Gas Man® Site License.
I wrote Gas Man® in 1980 because
"Uptake and distribution of anesthetic gases
is virtually incomprehensible"
wroteLawson: Gas Man Review, Anesthesia and Analgesia, August 1991
Pharmacokinetics is important !
Pharmacokinetics is important !
Pharmacokinetics explainswhat goes onfrom vaporizer to brain
Crucial to clinical practice
Goal
Inhalation Kinetics is not understood 1
1 Lawson D. Gas Man Review. Anes & Analg 8/91Cited: 1990 ABA In-Training Exam resultsCA3 resident graduates from US Medical Schoolsanswered 47% of questions incorrectly !
The Model = path of anesthetic tensionVaporizer
Breathing Circuit
Alveoli (lungs)
Arterial Blood
Tissues (VRG [brain], MUS,FAT)
Venous blood (coming back to lungs)
Alveoli (lungs, again)
Breathing Circuit (to be rebreathed)
The Model = path of anesthetic tensionVaporizer (DEL = delivered conc)
Breathing Circuit (Inspired on monitor)
Alveoli (lungs) (Expired on monitor)
Arterial Blood (not measured)
Tissues (VRG [brain], MUS,FAT)VRG = Vessel-rich = lots of blood flow = fast
Venous blood (coming back to lungs)
Alveoli (lungs, again)
Breathing Circuit (to be rebreathed)
Electrical model for inhalation kinetics
P = Partial Pressure or Tension (electrical V or E)
F = Gas Flow = Conductance (electrical G = 1/R)
C = Capacitance (electrical C)
= Anesthetic flow (electrical current = I)
CFRC
FFGF FVA
CCKT
DELP
CFAT
MUSF
FFAT
CMUS
CVRG
FVRG
IP E VRGPAPDEL
P P=
Electrical model for inhalation kinetics
P = Partial Pressure or Tension (electrical V or E)
F = Gas Flow = Conductance (electrical G = 1/R)
C = Capacitance (electrical C)
= Anesthetic flow (electrical current = I)
CFRC
FFGF FVA
CCKT
DELP
CFAT
MUSF
FFAT
CMUS
CVRG
FVRG
IP E VRGPAPDEL
P P=
Too Complicated
Inhalation Kinetics is not understood 1
1 Lawson D. Gas Man Review. Anes & Analg 8/91Cited: 1990 ABA In-Training Exam resultsCA3 resident graduates from US Medical Schoolsanswered 47% of questions incorrectly !
Gas Man® teaches inhalation kinetics effectively and enjoyably 2
2. Garfield JM, Paskin S, Philip JH. An evaluation of the effectiveness of a computer simulation of anesthetic uptake and distribution as a teaching tool. Med Educ. 1989; 23:457-462.
Gas Man Splash Screen
.9
Gas Man for WIN & MAC
More info:www.gasmanweb.com
Gas Man® results are correct
(A) Wash-in 360 minutes = 6 hr
15 minutes
(B) Wash-out
after breathing 1 MAC for 1 hr.
(C) Wash-out after breathing
1 MAC for 2 h.
(D) Wash-out after breathing
1 MAC for 4 h.
(E) Washout after breathing
1 MAC for 12 h.
According to:
Bouillon T, Shafer S. Editorial – Hot air or full steam ahead? An empirical pharmacokinetic model of potent inhaled agents. Brit J. Anaes. 84:429-431 2000.
GAS MAN® can be used two ways
Follow the book
GAS MAN® can be used two ways
Play and Explore
Follow the book
GAS MAN® can be used two waysFollow the book
Perform specific experiments
Learn the model's structure
Observe the model's behavior
Understand the structure-behavior relationship
Learn to predict & control behavior of model & patient
Learn to predict & control expired anesthetic tension
GAS MAN® can be used two waysFollow the book
Play
The Model - Gas Man® Picture
The Model - Compartments and Flows
VaporizerBreathingCircuit Lungs
Blood
------Tissues------BrainVRG
Mus FatVenousBlood
FGFFreshGasFlow
Alv(Lung)Vent
CardiacOutput
The Model - Return Flows
BreathingCircuit Lungs Venous
Blood
The Model - From Vaporizer to Brain !
Vaporizer
Brain(VRG)
Measurements we make
BreathingCircuit Lungs
Vaporizer
Setting Inspired Expired
BrainEEG,
BIS, PSI?HR,BP
Time, Uptake, and Delivered Liters and $
Questions on Model ?
5 minute course in inhalation kinetics
CONCEPTS
1. Tissue tensions (partial pressures) equalize (=)Tissue concentrations equilibrate (≠)
2. The One Compartment ModelStep Response is an exponentialLung wash-in (exponential - = 0.5 min) Tissue wash-in (another exponential - = 3 min)
3. Sequential Compartmentsdelays add to each otherBreathing circuit + Alveoli + Tissue
4. The Alveolar Tension Curve
A. Initial Rise - Alveolar Wash-In
B. Knee - Equilibration with Blood
C. Tail - Venous Return