Case today

[dabears505]

Working at an old surgery center locums. Haven't been here too many times. Equipment old and outdated.

Placed an LMA for a foot procedure. Hr, bp everything wnl. Etco2 reading 18. Tidal volumes regular spontaneously breathing 350 or so. Good waveform. Also noticed sevo reading 1.0 for inspired when dial set to 2.0. Also was using 100 percent o2, and machine reading inspired 02 50. Was crapping my pants with that c02, but everything else was normal. Is there something faulty in monitors that can cause everything to be halved? Like sevo was half, as was 02 and c02 was half of normal. Thoughts?

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[deleted162650]

Working at an old surgery center locums. Haven't been here too many times. Equipment old and outdated.

Placed an LMA for a foot procedure. Hr, bp everything wnl. Etco2 reading 18. Tidal volumes regular spontaneously breathing 350 or so. Good waveform. Also noticed sevo reading 1.0 for inspired when dial set to 2.0. Also was using 100 percent o2, and machine reading inspired 02 50. Was crapping my pants with that c02, but everything else was normal. Is there something faulty in monitors that can cause everything to be halved? Like sevo was half, as was 02 and c02 was half of normal. Thoughts?

I’ve run into this before. Assuming monitor is calibrated correctly, it’s usually because the sample line was not fully/tightly screwed into either the circuit/elbow or the gas analyzer and you are entraining room air. Easy fix.

 

[btbam]

Sample line loose. Just entraining room air, that’s why it’s reading 50% fiO2.

 

[IlDestriero]

Absolutely a sample line leak.
Seen it before.

 

[dabears505]

Would that cause gas concentration and etco2 to be half as well?

 

[coffeebythelake]

Would that cause gas concentration and etco2 to be half as well?

Uh.... yeah....

 

[drmwvr]

... Was crapping my pants with that c02, but everything else was normal....Thoughts?

Wondering why you were panicking.

 

[Ronin786]

I also wouldn't really sweat an EtCO2 with an LMA in somebody breathing spontaneously unless it was preposterously high.

 

[pgg]

Working at an old surgery center locums. Haven't been here too many times. Equipment old and outdated.

Placed an LMA for a foot procedure. Hr, bp everything wnl. Etco2 reading 18. Tidal volumes regular spontaneously breathing 350 or so. Good waveform. Also noticed sevo reading 1.0 for inspired when dial set to 2.0. Also was using 100 percent o2, and machine reading inspired 02 50. Was crapping my pants with that c02, but everything else was normal. Is there something faulty in monitors that can cause everything to be halved? Like sevo was half, as was 02 and c02 was half of normal. Thoughts?

Reading the sevo, O2 and CO2 at half normal points squarely at a loose sample line, as others have said.

I did want to make a point of this part though:

Also noticed sevo reading 1.0 for inspired when dial set to 2.0.

Volatile concentration measured by the gas analyzer, compared to the dial setting on the vaporizer, will be very different under some very common circumstances:
- low fresh gas flows
- more soluble agents
- early in the case when uptake is still high

In general, if you start a case and your inspired volatile concentration actually does equal the dial setting, your fresh gas flows are higher than necessary and you're wasting volatile.

 

[Planktonmd]

Yes, it's either the sample line or the filter on the gas analyzer.

 

[fakin' the funk]

Working at an old surgery center locums. Haven't been here too many times. Equipment old and outdated.

Placed an LMA for a foot procedure. Hr, bp everything wnl. Etco2 reading 18. Tidal volumes regular spontaneously breathing 350 or so. Good waveform. Also noticed sevo reading 1.0 for inspired when dial set to 2.0. Also was using 100 percent o2, and machine reading inspired 02 50. Was crapping my pants with that c02, but everything else was normal. Is there something faulty in monitors that can cause everything to be halved? Like sevo was half, as was 02 and c02 was half of normal. Thoughts?

This has happened about 1x/yr when I supervise CRNAs. The discussion hinges entirely on PE, as if there are no other causes of low etCO2

 

[vector2]

This has happened about 1x/yr when I supervise CRNAs. The discussion hinges entirely on PE, as if there are no other causes of low etCO2

Hopefully you explained to them the odds of having a PE massive enough to cause Etco2 18 but still have a normal BP and pulse ox waveform are essentially zero.

 

[IlDestriero]

This has happened about 1x/yr when I supervise CRNAs. The discussion hinges entirely on PE, as if there are no other causes of low etCO2

There are other causes of low EtCo2. I don’t think PE is even the most common one.

 

[dabears505]

I think that when you look at the monitor and see good waveforms and see an end tidal of 18, you should be concerned. Obviously after checking other vitals and seeing that they were normal, I was not as concerned. But I dont think its unreasonable to get worried upon seeing that low a number.

 

[Mman]

a loose sample line connection tends to cause a strange looking CO2 waveform beyond just a low reading