Body Simulation

Body Simulation is built around the excellent physiologic and pharmacologic models of N. Ty Smith, M.D. The software is integrated with many aspects of relevant physiology to present users with the most life-like PC based flat screen anesthesia simulation available.

 











About the Body Simulation System

VII. TEACHING WITH BODY SIMULATION FOR ANESTHESIA

Back to Body Manual Index | Next Chapter (VIII. Body Simulation Windows - The details)

Quick Start - Sample Scenarios

The Quick Start Section will get you started from the Windows desktop. In addition, it gives examples of six BODY scenarios:

  1. A clinical scenario: induction of anesthesia
  2. A physiologic scenario: denitrogenation and apnea
  3. A pharmacologic scenario: uptake and distribution of thiopental
  4. An anesthesia machine scenario: low-flow anesthesia
  5. A critical incident scenario: rapid hemorrhage
  6. An inhaled gas scenario: the second-gas effect.

Each scenario may have several subscenarios. In addition, a set of questions allows you to self-test what you have learned from the scenarios.

- Starting BODY for each scenario:

To start Body you may double click on the Body icon which was created on your desktop when the program was installed, select Body Simulation from the programs section of the Windows Start Menu, or find the directory where you installed Body, and double click on the "BodyAnesthesia.exe" file.

Clinical scenario: Induction of anesthesia

This scenario will acquaint you with using many of the features of BODY.

Select Patient:

  • Choose "Select Patient Now" from the startup screen, and select "pat01.pat".

Setup IV lines and fluids:

  • Go to "Setup IV Lines" from the View Patient page.
  • Select an IV line (eg. Rt. Antecubital - 18 ga.).
  • Click "Setup Fluids".
  • Click on the IV line "Rt. Antecubital" from Intravenous lines text box.
  • Click the "Add a New Fluid to this Line" button.
  • Select the type of infusion fluid.
  • Select the size of the infusion bag.
  • Select "Accept".
  • Click "Done" to close the window.

Setup drugs:

  • Click the "Drugs" button on the "View Patient" window.
  • Choose "Induction Agents".
  • Select "PENTOTHAL".
  • Ensure "25 mg" is set for concentration.
  • Select a 20cc syringe.
  • Click "Accept".
  • Choose " Neuromuscular Blocking Agents".
  • Select " SUCCINYLCHOLINE".
  • Ensure "20 mg" is set for concentration.
  • Select a 10cc syringe.
  • Click "Accept".
  • Click "CLOSE" to close the drug selection window.

Setup monitors:

  • Click on "Setup Monitors" on "View Patient" window.
  • Select ECG.
  • Select Pulse oximeter.
  • Select NIBP - 1 reading / 3 minutes.
  • Select Capnogram (CO 2 ).
  • Select Inspired O 2 .
  • Select "OK" to close this window.

Setup anesthesia machine:

  • Go to Anesthesia Machine (click "Gases" on the "View Patient" window).
  • Turn the O 2 flow to 5 l/min
  • Select "Done" to close the anesthesia machine window.

In the "View Patient" window start induction:

  • In the "View Patient" window set the drip rate:
  • Click the cursor on the right hand up arrow to increase the rate, down arrow to decrease the rate. A digital display gives the rate (cc/min).
  • Click once on mask to place mask.
  • Wait for one minute, for denitrogenation, if you wish.
  • To pass the time, talk to the patient. (Or click the fast forward button and watch the clock.)
    • Click on "dialog", lower right.
    • Click on the patient picture.
    • Click on "Open your eyes."
    • Click on "Close your eyes."
    • Click on "Take a deep breath," and observe the bag.
    • Click on "Can you hear me?" Listen for the answer.
  • To start injection, click on the inject button below the thiopental syringe.
  • Click again to stop injection at the desired dose.
  • Wait until patient becomes apneic and closes his eyes.
  • Click on the breathing bag to breathe for the patient.
  • Remember, if you want the patient to breathe, you have to click.
  • Check to make sure the twitch monitor is working by clicking on the train-of-four (TOF) image.
  • Don't forget to click the breathing bag.
  • To inject succinylcholine, repeat the clicking procedure outlined above.
  • When you think the patient is paralyzed, click on the TOF image.
  • Repeat, if necessary, until the twitch disappears.
  • Remove mask by clicking on the mask.
  • Insert endotracheal tube by clicking on the laryngoscope.
  • When prompted, set appropriate tube depth (as measured at the teeth).
  • Use up and down arrows to move tube. (The down button increases the value, and vice versa.)
  • Secure tube and inflate the cuff by clicking on the "Set tube" button.
  • Go to Anesthesia Machine.
  • Select the electronic control panel for the anesthesia machine.
  • Turn on ventilator.
  • Use the following settings
    • RR = 7.
    • TV = 0.9.
    • PEEP = 0.
    • I:E = 1:2.
  • Switch from Air to N 2 O.
  • Set N 2 O/O 2 to 50%.
  • Use isoflurane - it should already be selected as it is the default.
  • Set isoflurane to 1% by holding down the mouse with the cursor on the left side of the knob. To fine tune, you may click once for each 0.05% change.

Congratulations; you have just safely induced anesthesia.

 

Physiologic scenario: "How long do I have?"

This scenario is designed to allow the user to study the impact of denitrogenation on the maintenance of adequate oxygenation during apnea. Although there are three specific subscenarios - no denitrogenation, about one minute of denitrogenation, and about five minutes of denitrogenation - the user may modify this and other scenarios in many ways. For example, one may modify the duration of denitrogenation, the fresh gas flow, the initial pulmonary state of the patient, and the duration of the apnea. To modify the initial state of the patient, one may change lung parameters or shunt. The airway obstruction scenario will certainly make the scenario more interesting, but you must use thiopental to implement this incident, and this will make any comparison with other variations less accurate.

The following algorithm describes the second subscenario of "How long do I have?" To run the first subscenario, simply omit the denitrogenation part. To implement the five-minute denitrogenation subscenario, you may wish to put BODY Simulation into fast forward, until the last 30 seconds are reached.

Subscenario 2

Implementation (NB. This sequence is intended purely to demonstrate physiological principles. The use of succinylcholine without an anesthetic is not to be construed as acceptable anesthetic practice.)

Before running this scenario, you will wish to set up some variables to be plotted. The variables listed are just suggestions; you may plot different ones, if you wish.

You have a choice to follow the steps as presented after this paragraph, or select a "Quick Setup" for this scenario. To take the quick setup choice, launch Body and select the "Quick Setup Now" button. Choose the "HowLongDoIHave" option. The first 4 steps of this case will be done for you: Select Patient, Setup IV lines and fluids, Setup plots, and Setup drugs. (The HowLongDoIHave quick setup is provided as part of the Body Simulation for Anesthesia software package.)

Select Patient:

  • Choose "Select Patient Now", and select "pat01.pat".

Setup IV lines and fluids:

  • Go to "Setup IV Lines" from the View Patient page.
  • Select an IV line (eg. Rt. Antecubital - 18 ga.).
  • Click "Setup Fluids".
  • Click on the IV line "Rt. Antecubital" from Intravenous lines text box.
  • Click the "Add a New Fluid to this Line" button.
  • Select the type of infusion fluid.
  • Select the size of the infusion bag.
  • Select "Accept".
  • Click "Done" to close the window.

Setup plots:

  • From the "Scientific" menu item select Dynamic Time Plots.
  • Select "Add Variables".
  • Select the variables listed below.
    • Tracheal gas flow
    • Tracheal O 2
    • Tracheal CO 2
    • Pa O 2
    • PaC O 2
    • Pv O 2
    • Sv O 2
    • Sp O 2 (Hb sat aorta)
    • Sv O 2 (Mixed venous sat)
    • P O 2 in cerebral gray matter
    • % O 2 in lungs
    • Hb sat myocardium

Select "Done" to return to the time plots graph.

Select "Patient" from the "View" item of the main menu to return to the patient view. Note: An alternate method of bringing the patient window to the front is to click anywhere on the patient window.

Setup drugs:

  • Click the "Drugs" button on the "View Patient" window.
  • Choose " Neuromuscular Blocking Agents".
  • Select " SUCCINYLCHOLINE".
  • Ensure "20 mg" is set for concentration.
  • Select a 10cc syringe.
  • Click "Accept".
  • Click "CLOSE" to close the drug selection window.

Setup anesthesia machine:

  • Go to Anesthesia Machine (click "Gases" on the "View Patient" window).
  • Turn the O 2 flow to 5 l/min.

Freeze simulation, do more setup:

  • Click on the "Freeze" button on the "Squeeze" window to pause the simulation.
  • Place mask on patient by clicking on mask image on the "View Patient" page.
  • Go to Dynamic Time Plots from the "Scientific" menu item.
  • Set the time axis to 16 minutes.
  • Deselect the "Wrap" button, so the graph will not wrap around and overwrite the graphs after 16 minutes.
  • Click on "RECORD" if you want to produce a data file for this scenario.
  • Deselect the "Freeze" button to resume the simulation.
  • View the patient, begin the procedure:
  • Let the simulation run for one minute to denitrogentate.
  • Click on "inject," under the succinylcholine syringe.
  • Arrange the windows so the dynamic time plots may be seen.
  • If you want to observe in faster than real time, select the "Fast Fwd" button on the squeeze window.

NB: When you deselect the record button the data will be saved in a file. You will be prompted to enter an annotation, and for filename information. Click on "Replay", and select your file to observe what the recorded data look like.

Questions:

  1. Is denitrogenation really useful?
  2. In this healthy patient, is five minutes of denitrogenation significantly better than one minute?
  3. What is the longest you have ever required to complete an intubation?
  4. How often has that happened?
  5. Is it worth the extra time on all patients for this occasional patient?
  6. Does the presence of 100 % O 2 in the circuit make any difference? During the apneic period, change the flow from 100% O 2 to 20 % O 2 and observe the Dynamic Gas System screen or the Dynamic Time Plots.

 

Pharmacologic scenario: Uptake and distribution of thiopental

  • This scenario allows the user to examine the uptake and distribution of thiopental.

Select Patient:

Choose "Select Patient Now", and select "pat01.pat".

Setup IV lines and fluids:

  • Go to "Setup IV Lines" from the View Patient page.
  • Select an IV line (eg. Rt. Antecubital - 18 ga.).
  • Click "Setup Fluids".
  • Click on the IV line "Rt. Antecubital" from Intravenous lines text box.
  • Click the "Add a New Fluid to this Line" button.
  • Select the type of infusion fluid.
  • Select the size of the infusion bag.
  • Select "Accept".
  • Click "Done" to close the window.

Setup drugs:

  • Click the "Drugs" button on the "View Patient" window.
  • Choose "Induction Agents".
  • Select "PENTOTHAL".
  • Ensure "25 mg" is set for concentration.
  • Select a 20cc syringe.
  • Click "Accept".
  • Choose " Neuromuscular Blocking Agents".
  • Select " SUCCINYLCHOLINE".
  • Ensure "20 mg" is set for concentration.
  • Select a 10cc syringe.
  • Click "Accept".
  • Click "CLOSE" to close the drug selection window.
  • Setup plots:
  • Select "Dynamic Time Plots" from the "Scientific" menu item.
  • Select "Add Variables", and use the "Plot Drugs" screen.
  • Select PENTOTHAL. Concentration is plotted by default.
  • Click on the desired compartment.
  • Repeat for each compartment.
  • Select the following compartments.
    • Aorta
    • Vena cava
    • Myocardium
    • Brain gray matter
    • Kidney
    • Liver
    • Muscle, skin
    • Fat
  • Click on the "Mass" radio button to plot mass.
  • Click on any desired compartment, but at least Fat and Muscle, skin.
  • Select "Done" to return to the graph window. Arrange the windows as desired.
  • Set the time axis to eight or 16 minutes. The former duration will show more detail, the latter the longer-term effects.
  • Deselect the "Wrap" button to have the plot stop at the end of the page.
  • Select the "Record" button if you'd like to save your results.

Setup the anesthesia machine:

  • Go to the Anesthesia Machine selecting "Gases" from the "View" item of the main menu.
  • Turn on the O 2 flow to 5 l/min.
  • Click on "DONE" to return to the patient view.
  • Place mask on patient by clicking on the mask image.
  • Denitrogenate for one minute.

Continue with the procedure:

  • Click on the "inject" button just below the syringe to inject the thiopental.
  • View the Dynamic Time Plots.
  • If you want to observe in faster than real time, select the "Fast Fwd" button on the squeeze window.
  • Deselect the "Record" button if you had previously selected it.

Questions:

  1. What is the role of fat in the rapid distribution of thiopental?
  2. How about muscle?
  3. How well do arterial (aortic) blood concentrations initially relate to those in the brain or myocardium? Does this change as a function of time?
  4. Repeat this scenario by selecting the same patient, but with a blood volume of 4000 ml instead of 5000 ml. What happens to the distribution of thiopental? Why?

Repeat the case with the same patient "Pat01.pat" except perform a rapid hemmorhage scenario on the patient before starting (see the next section for an example of the scenario). Bleed the patient at a rate of 200 ml/min for 10 minutes. You should answer the following questions before starting the second case.

  1. What do you anticipate will happen to the cardiovascular and respiratory systems in the low-volume situation? Why? - The initial mean arterial pressure was the same in both scenarios in this healthy young patient.
  2. Repeat these two scenarios, this time either plotting cardiovascular and respiratory variables of your choice, or watching the variables on the Monitor screen. You may use the instructions in the "Rapid-hemmorhage Scenario" to set up the plot and implement the bleeding.
  3. With which "patient" does thiopental have a greater impact on the cardiovascular system?
  4. What should you do for a hypovolemic patient before injecting thiopental, if you use that agent at all in this situation?

 

A critical incident scenario: Rapid hemorrhage

This scenario allows the user to examine the effects of blood loss and baroceptors on patient vital signs.

Use a Quick Setup to setup the case:

Select "Quick Setup Now", then choose "BasicInductionHealthyPatient".

Setup IV lines and fluids:

Quick Setup has done this for you.

Setup drugs:

Quick Setup has done this for you.

Setup plots:

  • Select "Dynamic Time Plots" from the "Scientific" menu item.
  • Select "Add Variables", and use the "Plot General" screen. Select the following:
    • Total blood volume
    • Cardiac output, pulmonary artery
    • Mean Arterial Pressure
    • Heart rate
    • Stroke volume
    • Myocardial contractility
    • Kidney arterial resistance
    • Kidney venous compliance
    • Extracellular fluid
  • Deselect the "Wrap" button to have the plot stop at the end of the page.
  • Set the time scale on the plot to 16 minutes.
  • Select "Record" if you want to save your data for this scenario.
  • Setup the incident:
    • From the "Problems" item of the main menu, select "Critical Incidents"
    • Select the bleeding incident - 100 ml/min for 10 minutes.
    • Set the trigger event as "1 minute" from "Now" (this should give about a 1 minute stable baseline on your plots before the incident starts).
    • Select "Accept Trigger Events", then select "Close" to close the window.
  • Continue with the case:
  • If you want to observe in faster than real time, select the "Fast Fwd" button on the squeeze window.
  • When you are satisfied with the results, deselect the "Record" button if you had previously selected it.

Questions:

  1. Which variable is the most profoundly affected?
  2. Why does mean arterial pressure change very little?
  3. What happens to kidney blood flow?
  4. Do the cardiovascular changes continue after the bleeding stops? (Hint: BODY has a baroceptor control system that affects heart rate, myocardial contractility, arteriolar resistance, and venous compliance. These components will act as long as the mean arterial pressure is less or greater than the set point. In addition, each component of the baroceptors has a different rate of action. And don't forget the extracellular fluid compartment.)

Repeat the same scenario, but turn off the baroceptors just before the hemmorhage. (Select the "Problems" item of the main menu, then the "Patient Condition" item, and the "Baro Control" tab.)

Repeat the same scenario after equilibration with 2% halothane.

Halothane shuts off the baroceptors. Are there any differences between halothane anesthesia and the simple lack of baroceptors? What are they?

What other conditions could "shut the baroceptors off?"

 

Anesthesia Machine scenario: Low-flow anesthesia

This scenario examines the safety of low-flow anesthesia, the estimation of the various flows and concentrations, and the usefulness of certain monitors.

Subscenario 1: What is the minimal fresh-gas flow with room air or with 100% O 2 ?

Select patient and setup for the scenario:

  • Choose "Select Patient Now" from the startup screen, and select "pat01.pat".

Setup for the scenario as was done in the clinical scenario "Induction of Anesthesia". Follow the setup up to "Setup anesthesia machine".

  • Setup plots:
  • Select "Dynamic Time Plots" from the "Scientific" menu item.
  • Select "Add Variables", and use the "Plot General" screen. Select the following:
    • Hb sat Aorta (SpO 2 )
    • Hb sat Vena cava (SvO 2 )
    • PaO 2 (0-120mmHg)
    • PaO 2 (0-760)
    • PvO 2 (0-120mmHg)
    • Depth of Anesthesia
    • Alveolar conc left (or right) - Agent 1
    • Alveolar conc left (or right) - N 2 O
  • Deselect the "Wrap" button to have the plot stop at the end of the page.
  • Set the time scale on the plot to 16 minutes.
  • Select "Record" if you want to save your data for this scenario.
  • Setup anesthesia machine:
  • Go to the Anesthesia Machine selecting "Gases" from the "View" item of the main menu.
  • Set the Air flow to 1.0 lpm.
  • Keep the air mode (i.e. do not switch to N 2 O). Keep at 100% room air, i.e., 20% O 2 .
  • Observe the plots in Dynamic Time Plots.
  • Induce anesthesia, continue with scenario:
  • Induce anesthesia with thiopental and succinylcholine - use the clinical scenario "Induction of Anesthesia" as a guideline if you are not sure how to proceed. It is not necessary to denitrogenate in this scenario.
  • Are you in a hurry? You will obtain essentially the same results by simply placing the mask on the patient's face in lieu of intubation. The mask does increase the dead space, of course.
  • Are you still in a hurry? Switch to the fast-forward mode by typing "F." This will allow you to proceed through the various sub scenarios at a faster than real time pace. You will not obtain the feeling that goes with real-time simulation, however.

What happens?

Now increase the FGF by increments of 1 l/min until the PaO 2 reaches 110 mm Hg.

What flow rate is required to achieve this level? Why is it so high?

Consider expired O 2 concentration and dilution of O 2 in the inspired gas. It will help if you examine the Dynamic Gas Plot (from the scientific menu) window and observe the expired concentration of O 2 .

  • Change the concentration of O 2 to 100%.
  • Decrease the FGF to 1 lpm.
  • Decrease the FGF by 0.1 lpm decrements until the PaO 2 reaches 110 mm Hg.

Questions:

  1. What is that flow rate?
  2. What is an insufficient FGF now? Would you have predicted this? What is the probable O 2 consumption in this patient?

 

Subscenario 2: What is the lowest concentration of O 2 at a given flow?

Set up as with Subscenario 1.

Start with 0.5 lpm FGF flow and 100% O 2 .

  • Decrease the O 2 concentration by 10% decrements until the SpO 2 begins to decrease. You will have to wait for two minutes at each step. (If you are in Fast Forward, you can use either the clock or the vertical lines on the plot page as a time indicator.)
  • Go back to 100% O 2
  • Change the FGF to 1.0 lpm
  • Repeat the decrements of O 2 , as above.
  • Increase the FGF by 0.5 lpm increments and repeat the O 2 decrements, until the O 2 sat no longer drops at 20% O 2 .

Subscenario 3: How much inhaled agent do you need at low flows?

Administering potent inhaled anesthetics under low-flow conditions can be tricky. Practicing on BODY can help you in the real clinical situation. Since the uptake of an anesthetic depends on the total amount delivered to the body, low-flows, by definition, may not supply enough agent during induction to rapidly induce a patient. Concentrations that would be positively scary under high-flow situations may be inadequate during low-flow situations.

If you wish to use an agent other than halothane or isoflurane:

  • Open the anesthesia machine window
  • Click on "Select Agent"
  • Click on the bottle containing the desired agent. A label of that agent will appear in place of the previous agent.

Set up as with Subscenario 1.

  • Start with 0.5 lpm FGF flow and 100% O 2 .
  • Type "F" on your keyboard for fast forward.
  • Dial in 3 MAC of the agent, assuming a healthy young male.
  • Observe the changes in agent concentration on the machine or monitor, or time how long it takes the patient to close his eyes. If you wish to see the changes in concentration of say arterial blood, brain, and muscle, as a function of time, you should plot the changes (see below).
  • Dial the maximum possible concentration allowed by the vaporizer for that agent.
  • Again, observe the changes in agent concentration.
  • Change agents. If you used an agent with a relatively high solubility, select an agent with a low solubility, especially desflurane.
  • Examine as many agents as you wish.

Repeat the entire subscenario with fresh-gas flows of 1.0, 2, 5, and 10 lpm.

If you wish to follow the course of the changes of concentrations of agent in the various compartments, or if you wish to follow the cardiovascular or cardiorespiratory changes, you will need to use one of the two plot options.

Plotting concentrations:

  • Select "Dynamic Time Plots" from the "Scientific" menu item.
  • Select "Add Variables", and use the "Plot Drugs" screen.
  • Select the required drugs, compartments, and concentration or mass.

Plotting cardiorespiratory or pharmacokinetic variables:

  • Select "Dynamic Time Plots" from the "Scientific" menu item.
  • Select "Add Variables", and use the "Plot General" screen.
  • Select the required variables.

 

Set up the plot page:

  • Deselect the "Wrap" button to have the plot stop at the end of the page.
  • Set the time scale on the plot to 32 minutes.
  • Freeze the simulation (Use the freeze button of the "squeeze" window) before setting up the other details, such as agent concentration.
  • Select "Record" if you want to save your data for this scenario.

Using FD/FA. A very interesting educational tool is FD/FA, the ratio of the dialed to the alveolar concentration. The higher the ratio, the higher the dial setting must be to achieve the desired effect.

This scenario was performed with spontaneous ventilation. Any of the scenarios may be repeated with mechanical ventilation. Be sure to have the patient well anesthetized and paralyzed before starting the inhaled anesthetic if you use mechanical ventilation. If you want to remove the effect of injected anesthetic agents on the uptake and distribution of inhaled agents, feel free to use only paralysis; just be aware that this is not standard anesthetic practice.

Questions

  1. Can you induce an inhaled anesthetic, given the upper concentration limits on the vaporizers, with any of the agents if you start with low-flow conditions?
  2. Would it be useful to induce anesthesia with an injected agent first and then proceed immediately to a closed circuit system?
  3. Is this true of all the available inhaled agents?
  4. Is an agent with a low or a high blood-gas partition coefficient more likely to be useful during low-flow conditions? Which of today's agents are therefore more suitable for low-flow anesthesia?
  5. What are the other implications of starting at the time of induction with a closed-circuit system?
  6. What do you gain by using flows that are higher than 0.5 lpm?
  7. What do you lose?
  8. What are the advantages and disadvantages of closed-circuit systems?
  9. What do you gain and lose by using N 2 O in a low-flow situation?
  10. What concentration of N 2 O is optimal under these conditions?
  11. Is an agent monitor useful during low-flow anesthesia?
  12. Is an O 2 monitor useful?
  13. How "fast" should those monitors be?
  14. How about a monitor that measures nitrogen?
  15. Would a multiplexed mass spectrometer be useful during low-flow anesthesia, as compared with a mass spectrometer for each patient?

 

An inhaled gas scenario: The second-gas effect

Learn what the second gas effect is. Explore some details about how it may be used to your advantage, or how it may work against you.

Subscenario 1: N 2 O and a potent inhaled agent

Use a Quick Setup to setup the case:

Select "Quick Setup Now", then choose "BasicInductionHealthyPatient".

Setup IV lines and fluids:

Quick Setup has done this for you.

Setup drugs:

Quick Setup has done this for you.

Setup plots:

  • Select "Dynamic Time Plots" from the "Scientific" menu item.
  • Select "Add Variables", and use the "Plot General" screen. Select the following:
    • inhaled concentration, left lung.
    • depth of anesthesia.
    • tracheal flow rate or tidal volume.
    • aortic O 2 tension (PaO 2 [0-120mmHg]).
  • Deselect the "Wrap" button to have the plot stop at the end of the page.
  • Set the time scale on the plot to 32 minutes.
  • Select "Record" if you want to save your data for this scenario.

Setup anesthesia machine:

  • Go to the Anesthesia Machine selecting "Gases" from the "View" item of the main menu.
  • Change to N 2 O mode.
  • Set the N 2 O flow to 3.0 lpm.
  • Set O 2 flow to 1.0 lpm O 2 .
  • Set Isoflurane to 4%.
  • Close the Anesthesia Machine window and return to the View Patient window.
  • Continue with scenario:
  • Place the mask on the patient by clicking on the mask icon.
  • Rearrange the windows so you may observe the plots in progress.
  • Optionally, select "Fast Fwd" from the Squeeze window.

You may repeat this subscenario with other potent inhaled agents. Also, repeat it without N 2 O.

Repeat the scenario with O 2 and inhaled agent only, with O 2 and N 2 O only. Repeat the N 2 O-O 2 induction and observe the Dynamic Gas Display screen. Watch the relative concentration of O 2 . Now keep the N 2 O on for about 20 minutes and remove the mask. Use both the Dynamic Gas Display screen and PaO 2 in the Dynamic Time Plots to observe what happens to O 2 . This used to be called "diffusion hypoxia", but it is actually the second-gas effect in reverse. You may wish to record or print out the plots of all of these subscenarios, so that you can compare the differences among them. You may also wish to add other variables.

Questions

  1. Does the presence of N 2 O influence the rate of induction with a potent inhaled agent?
  2. Does the presence of an inhaled agent influence the induction with N 2 O?
  3. The bottom line is the rate of change of depth of anesthesia. Does the presence of N 2 O really speed up induction of anesthesia? We have not included the delayed administration of N 2 O, as suggested by Dr. Eger, but you may try that if you wish. Please be aware that no breath holding or coughing, due to the irritant effect of an inhaled anesthetic, is not yet implemented in BODY.
  4. Why did the concentration of O 2 increase during induction of anesthesia in the presence of N 2 O?
  5. Why did it decrease after removal of the mask during the administration of N 2 O?

Hint: What is the role of the relative blood/gas partition coefficients of N 2 O and N 2 ?

Set up your own scenarios :

You can set up a large number of scenarios with BODY. For example, you can customize any of the scenarios described above and save as a Quick Setup. You may wish to set up your own scenarios with different anesthetic agents.

Dial-a-Patient and Dial-a-Drug is a very useful tool to implement scenarios. And use the Incidents and Conditions as part of your scenarios, as we have done with bleeding in the Rapid Hemorrhage scenario. Practice administering fluid during the bleeding, for example.

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