Scenario Respiratory Help

[JSlimmon]

I've been running into an interesting problem when I develop scenarios and hope that someone can help me with it.

When creating scenarios I have been adjusting the Shunt Fraction to change the patient's oxygen saturation. However, when I then change the Fraction of Inspired Oxygen Override when oxygen is administered, the patient's saturation will improve but then he stops breathing and eyes close.

This has happened in different scenarios and I'm wondering if it has to do with the level of oxygen that gets to the sim's "blood". Do I have to change O2 Consumption as well?

Thanks for the advice.

[AFmedic]

Could be a couple different things. What are the numbers on the hud when he goes out? I've never had good results making drastic changes to the shunt fraction, i find it's safer to play with the oxygen consumption or fraction of inspired 02 override. If his gasses are getting way out of whack he may actually be passing out because of them.

[iregbnz]

What other events are programmed into the scenario could they also be having an effect on the simulated patient, especially if the myocardium has become ischaemic.

Using O2 consumption in conjunction with the Shunt fraction is the best way to control SpO2 and gives a more realistic physiology also adjusting tidal volume and respiratory factors alters the SpO2

You should while designing your scenario turn on the recorder function in the software.

Get the saturation you require by adjusting the O2 consumption and Shunt fraction then use the Fraction of O2 override then adjust the shunt fraction again to get back to the desired saturation

Once you are happy with the saturation then add the cardiovascular parameters and see if your patient responds the same

Then drag and drop the last of each parameter into each event in your recorder list to the state you are working on in your scenario editor and this should hopefully enable you to see where the problem lies

Hope this helps

[sabot]

Take a close look at your CO2 levels while this is happening. I have found that sometimes, using FiO2 aggressively, I have brought the CO2 too low and knocked out the resiratory drive. This seems to be especially true with a high tidal volume.

Hope this helps,

Ken

[JSlimmon]

Thanks for the advice all. I wasn't using the O2 consumption and I'm sure that the respiratory drive is being knocked off due to low CO2 levels. I'll play around with the O2 consumption and hopefully things will move more smoothly.

[jcorvino]

I had a similar problem that wasn't necessarily related to the shunt fraction parameter or other parameters. The eyes would close and it would stop breathing...A temporary workaround is to change the default setting for the Chest Compression Efficacy from 100% to 0%. This is found in Condition/Show Trauma/Chest Compression Efficacy. Not sure how this will affect the other parameters.

Hope this helps.

[airresq]

Hi just a quick question when he goes out what is the ischemic index on the HUD showing/

[JSlimmon]

Ischemic index was normal - his heart kept beating strong. I've tried making changes with O2 consumption and also being a little more selective with the FiO2 and have had much more success. Now, I just adjust the FiO2 until the O2 sat is where I want it. I don't follow the chart provided in the notes anymore.

[ntekancic]

The problem that you are experiencing with moving the shunt to improve oxygenation and applying fraction of inspired O2 at the same time is that the software is responding correctly to the sudden high PAO2 and O2 comsumption rate. This is causing a quick drop in PACO2 and once the level falls below 38.4 the mannequin will pass out. (stop breathing and close eyes) until the PACO2 level stabilizes to 40.0 again. This can be avoided by doing one of two things. Decrease the shunt at lower values or simply going to the respiratory tab/respiratory control/CO2 set point. and setting the value to a lower value. This will allow the mannequin to avoid passing out from decreased PACO2 and increased PAO2. I hope this answers your question.

[JSlimmon]

That makes sense. Sometimes these are too realistic ;) Thanks for the help everyone.