METI programming
From WickedSim
The basic selling point of METI's human patient simulators (HPS, ECS, and the upcoming iStan) is their physiological model. With this in mind, programming the simulator can be broken down into the physiological philosophy and the fancy electronic blackboard philosophy. Aside from strictly programming the scenario, the simulator can also be used on the fly. The same principles apply there. Before going any further, please note that this is not a METI programming manual or a collection of METI programming tips and tricks, it is an introduction and overview of what the simulator is capable of and how you can approach programming it.
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Overview of the Software Package
The software is divided into two programs: the HPS and the Waveform Display. The HPS controls the mannequin and displays its vitals to you. The Waveform Display controls what learners will see on a monitor attached to the control computer.
The HPS is divided into two main portions on the screen: the HUD and the tabs. Of note, there is also a 'connect' button in the top right corner of the window that lets the user connect the computer to a mannequin. The prominent 'save' button in the top left corner of the window should never be used unless you are making your own patient, which you shouldn't need to do. When you choose to stop a patient, it will always ask if you want to save it. Again, hit no. You can't overwrite the standard patients that come with your package, but you can overwrite your own patients doing this unless you've disallowed the HPS user on the laptop to write to that file using your Administrator account.
The HUD gives you every vital sign you could want for your current patient. You can't even display most of these vitals on the monitor using the Waveform Display. However, if you are using the physiological model, these can be useful in creating accurate scenarios.
The tabs are the most important part of the HPS whether you are programming physiologically or not. Left to right, they are simulation, scenario, condition, drugs, fluids, cardiovascular, and respiratory. Each one has sub-tabs.
The Tabs
Any tab can be detached so you don't have to go hunting for it when you're running a scenario on the fly. Search for the detach tab button in the HPS window. Detaching the tab will keep you on the current sub-tab. All overlapping detached tab windows may be easily located by pressing the F9 key. The F9 key will automatically minimize and move all windows on the desktop into view to be selected. Changes made in any detached tab will carry over to other tabs and the main window, but changing sub-tabs in the detached tab won't make your main tab change its focus.
Here is a brief summary of the main seven tabs. The simulation tab is a description of your patient. This has no effect on anything, but can be used as a script or a prompt for the controller to see what the scenario is about. Alternatively, you could write a separate script, print it out, and ignore this tab. That's one fewer tab to worry about.
The scenario tab is where you can program all your scenarios ahead of time. There are sub-tabs for playing scenarios and editing scenarios. You can edit scenarios while you are playing another scenario if the simulation session gets really slow or you happen to have a burst of inspiration and don't want to forget it.
The condition tab can be used with the TDCK to simulate trauma bleeding, sludging, and other liquid events. This is also the place you'll find miscellaneous conditions such as eye blink, needle decompression enabling, breath and bowel sounds, etc. Some of these may be found elsewhere in the tabs, some not. Nothing here will affect the physiology of your patient.
Pre-programmed drugs can be administered using the drugs tab. If you have carefully programmed your patient following physiologically accurate states, these drugs will work as expected unless you overdose them. Be very careful administering drugs! You can't take them back. If you give the wrong drug or too much of a drug, you'll have to restart the scenario. If you are not programming physiologically, this tab should be ignored unless you find any of the drugs to be good as shortcuts. For example, succinylcholine will almost always act as its supposed to and can be a useful shortcut for getting the patient to be temporarily paralyzed.
The fluids tab's usefulness also depends heavily on whether you are programming physiologically or not. If you are, then you will see fairly accurate changes in vital signs when fluids are given or removed. Of particular use is the timer function, which you can use to draw off fluid over time simulating a slow bleed. If fluid is given over time you can superimpose that new condition and the two will cancel out to the extent that they are equal and opposite. If one type of fluid is being lost (blood) while another is being given (saline), you'll see an accurate simulation of the result. If you are not programming physiologically, this tab's sole purpose is to quickly lower the blood pressure, commonly referred to as 'bleeding your patient.'
The last two tabs will be the most useful because they are the most physiologically accurate tabs. Nearly every item in cardiovascular and respiratory can be used to make an accurate change in the mannequin. When describing METI's physiological model, these two tabs are the ones used to set the model conditions. A more detailed description follows in the programming section.
Programming the Simulator
Programming the simulator is generally a several step process. To begin, load a patient. A good starting point is METI's 'Standard Man'. The other standard METI patients may be good for other scenarios, but may be easier to familiarize yourself with one and use it for all purposes rather than spending time learning how each patient responds to your programming.
States are used to simulate the progression of a medical situation. A state is a point where every vital sign is defined to your liking. You could make it so that the entire scenario is a timed transition through states, or you could make those transitions manually by not using timers and just move from state to state as needed.
Before you begin programming, always create a folder in your users file where the new scenario may be saved. Then, open and turn on the recorder by selecting the "Record" button (located above the HUD in the main window).
Scenario scripts are programmed from within the scenario tab. Under the scenario tab, click on the arrow next to "Player" and choose "Editor." Next, select new scenario to begin programming a scenario. You'll need to create a new state first. It's a good idea to make the very first state in a scenario completely empty or at least a stable state, as this is the state that will be loaded up by default when you play the scenario. Choose the order of your states carefully, you won't be able to reorder them later and will have to delete them and recreate them if you want to clean up your scenarios.
You can select to add new events to your scenario states and change the outcome for that state. If you pick new 'set' event, this gives you the option of setting any parameter that you could otherwise set by finding it in a tab. Sometimes the names are not identical to the names given elsewhere, but they are similar. For instance, using new 'set' event you can choose to set the patient's respiratory rate factor to 2 in order to make him breathe twice as fast. You could have done this using the respiratory tab, but now whenever this state is loaded, it will happen automatically. That's the advantage of pre-programmed states. Another good event you can add is 'multiply'. This is similar to set, but instead will take whatever the numerical parameter is and multiply it by the value you give.
For faster programming, first select the parameter you want from under its main tab rather than choosing from within the Editor window. For example, if you want your patient to have ventricular tachycardia, select that rhythm from cardiac rhythm override under the Heart subtab within the Cardiovascular tab. Your selection will now appear in the Recorder window. Click on and drag your selection from the Recorder directly into the correct state in the scenario window, hit save, and ta-da, the event is programmed.
Programming with the Recorder has the useful advantage of allowing the operator to see how the simulator will respond to each change before it is added to the script.
Transitions can also be useful. Think of a transition as a conditional statement. If this happens, that will result. For example, if his respiratory rate drops below 10, he'll go into a state you've called dyspnea. Another use of transitions can be to loop a set of vital signs, particularly ischemic index (II). II is a made-up factor that controls how close the simulator is to spiraling down. Below 0.9, he'll experience ST depression. Below 0.6, he gets PVCs. Below 0.4, he gets VT. After one minute of that he gets VF. After one minute of that he's in asystole. You can imagine that it's important to loop the II if you want to maintain an 'unstable' state for some time to make a teaching point. This can be done by creating a transition that states "if II < 0.91, set II to 1.0". No matter how bad it gets, he'll always stay between 1.0 and 0.9. Alternatively, the II sensitivity and II averaging can be set so that he spirals faster or slower.
Next, a brief outline of the two main programming philosophies surrounding METI.
Physiological Programming
Physiological programming is the art and science of getting the mannequin to exhibit vital signs consistent with a real patient in the same situation by manipulating the underlying causes of his condition. It is accomplished by manipulating the values in the right four tabs. If you know the inner workings of a certain medical condition, a good place to start is by hunting down the associated parameters in a tab (systemic resistance, venous capacity, arterial elastance) and changing those parameters. You can then fine-tune the scenario, because Standard Man's physiology is not identical to the average person's physiology, not that any two people are identical anyway. However, because the responses are not completely real, it can be frustrating to play with the model until it reacts appropriately, and many things are impossible to program because they don't fall neatly into one of the cardiac or respiratory tabs. For instance, there is no way to simulate an AV heart blockage in order to induce 3rd degree block. You can simply choose to override the cardiac rhythm, but the defeats the purpose of programming physiologically accurate scenarios.
Any overrides (heart rate, breathing, etc) that you use will break the physiology because that value will be frozen and disconnected from the rest. This can make programming the scenario feel like driving a three wheeled car on a windy day. Essentially, there are really excellent scenarios that can be programmed using this model and there are some scenarios that will not work until the physiological model is expanded to include more parameters.
Pros
- As physiology improves, more scenarios are possible.
- Many scenarios provide a realistic situation for the learner where interventions produce quick, believable results.
- You've paid for the physiology, it's a shame not to use it.
- Vital sign changes are smooth and natural.
Cons
- Steep learning curve.
- Must anticipate many of the learner's actions, especially if they require complicated changes to the patient.
- Limited scenario programming ability. Overrides often essential; breaks the simulation.
- Scenarios take much time to program.
- 'METI' physiology, not necessarily human physiology.
Non Physiological Programming
To 'turn off' the physiology of the METI system, find the three baroreceptors in the cardiac tab and turn them to 0. Also put ischemic index sensitivity to minimum (0.1) and ischemic index averaging to maximum (0.99). Now you can change respiratory rate (RR), heart rate (HR), and blood pressure (BP) almost independently. Since these are essentially the only vital signs displayed on the monitor and the learner doesn't need to see how you got them, you're all set, right? Any other conditions such as sounds work as normal.
Once you've turned off the physiology, the RR can be changed through the RR factor or fixed RR under the respiratory tab. This will not affect HR or BP, but it will make the mannequin physically breathe faster. There is a maximum of 40 rpm. Also use tidal volume to adjust how much you want the chest to rise, but be careful that the lungs do not fill past 1500 ml each or you will have problems with your hardware.
The HR can be changed through HR factor or fixed HR under the cardiac tab. This will not change RR, but will change the frequency of beats when the chest is auscultated and it will change the BP in a direct relationship. The maximum using factor is 180 bpm, the maximum using fixed is much higher, but the Waveform Display won't show the right waveform for the number displayed. The minimum for either is 31 bpm.
The BP is the trickiest vital sign to change because METI does not provide a simple way to do it. There's a simple way to do this, a slightly more complicated way, and a really complicated way. The simplest way to do it is to use Contractility Factor: Left Ventricle (LVC) under the cardiac tab. HR and RR don't change, BP changes directly with LVC, but the relationship is not linear. Tuning LVC down will produce a sharp decrease in BP. Tuning it up will produce a linear change up to about 140 systolic depending on the HR, after which the BP begins to level off. At extreme levels of LVC the BP will actually drop a few points. At extreme highs or lows, BP fluctuates. Of special note is that at extreme lows, the BP will sometimes cause the II to drop below 0.9 even with the IIS set to almost nothing. What this means is that you'll get an instant 20 point drop in BP at that cutoff.
A slightly more complicated solution is using both LVC and fluid loss in conjunction. The advantage here is that fluid loss will allow for a more linear drop in BP, so it's especially useful for shock scenarios. However, this means you have to be paying attention to two tabs that will interact with one another. The relationship between LVC rise and fluid loss drop is not linear.
If you feel the need to control diastolic blood pressure, a far more complicated solution exists. While using LVC for systolic pressure, also head to the elastance parameters under the cardiovascular tab, systemic sub-tab. There are three of them and they all do the same thing for this purpose: increase pulse pressure. Your order of operations then becomes: decide what your pulse pressure should be and set it with elastance, bring your pressure up or down using LVC, fine-tune your BP using both.
Non physiological programming is far simpler than its counterpart, but there is more to say about it because the simulator uses physiology by default and you have to cheat it to get it to act this way. One thing to note is that you don't necessarily need to use strictly one or the other. Often, keeping the baroreceptors at default values and changing BP or HR is sufficient to achieve a desired state because BP and HR are inversely related. The key with this philosophy is you want and get highly reproducible vital signs, sacrificing the ability to use physiological shortcuts such as drugs with any accuracy.
Pros
- Simple to learn and use, pre-programmed or on the fly
- Highly reproducible
- Good for making specific teaching points, drawing out unstable situations, etc.
Cons
- BP / HR relationship cannot be completely disabled so an independent formula for BP cannot be established using only LVC.
- No direct control of BP from METI.
- No physiological accuracy, waste of resources, fighting the simulator.
- METI sponsored events (such as HPSN) are generally not supportive of this style of programming.
Other Points of Note
If you have one of METI's simulators or are considering purchasing one, there are a few things you ought to know:
- Technically, the METI platform lets you write a script (scenario) within the program, not a program of your own. You don't compile it, it doesn't work as a stand alone project.
- METI simulators are driven by G4 Mac laptops. On one hand, it would be useful to familiarize yourself with the OS X platform if you plan on using their products. On the other hand, Apple (Mac) wrote the book on how to be user friendly.
- You cannot modify the computer from its original form in any way, except with upgrades as directed by METI. This means you can't install new software or even plug the computer into any local network or the internet. You can't change the files supplied by METI (lung sounds, bowel sounds, any configuration files) and there are no tools to modify the interface or any of the physiological models. Doing any of these things will void the warranty.
- There is a Pharmacology Editor available from METI that will allow you to change drug responses and add your own drugs. The impact and useability of this has not yet been attested to in the market.
- Several groups have created scenario packages available for purchase. Of particular note is the Program for Nursing Curriculum Integration or PNCI. These take advantage of METI's physiology and are generally well structured and documented. It may be considered quite expensive if you're on a tight budget, but as some might say, you get what you pay for....
- The HPS (version 6.4) is the program used to manipulate the mannequin and create scenarios. HPS (for Human Patient Simulator) is also the name of METI's line of high end mannequins. They are not the same thing.
