lessons learned, Waveform Capnography

[Guest guest]

From one of the ACEP lists, forwarded by permission, and with a request for

other lessons learned to be passed back to Miami FD

ck

S. Krin, DO FAAFP

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I fully agree that waveform capnography is tremendously helpful in managing

intubations and belongs on the EMS trucks, but we want to make everyone

aware of a simple glitch we found in our EMS use, one that’s not likely to be

seen in OR/ICU/ED (where patient and device don’t move). A loosely connected

sensor/filterline may show a solid straight black line, but may NOT be sensing

the patient’s CO2. If the waveform line is perfectly straight (horizontal),

this is overwhelmingly likely to be a poor sensor connection, NOT a misplaced

tube or problem with the patient. I presented this at the Eagles “EMS State

of the Science†course in Dallas. Several other EMS Medical Directors with

same device (LP12) had seen the same “solid straight flat black line at

zeroâ€

but most didn’t realize the cause (I think it was just Jui, MD, who

caught it too)—and we all were previously taught that this type of tracing

meant that ETT was misplaced (or patient truly DEAD). Please check your

capnography system for same concern, and let EMS personnel know so that they

can

recognize and troubleshoot. If user doesn’t recognize that the sensor is

simply loose (machine does NOT give any indicator warning), the user may

respond

by removing/replacing a correctly placed tube, or terminate resuscitation

efforts because it looks like ETCO2 is zero.

More info: We implemented waveform capnography in City of Miami Fire

Rescue using the LP 12 with Oridion Microstream module. The sensor/filterline

screws into the monitor “until finger tight†but does not lock into place.

As

the line is screwed in, the tracing on the screen goes from a dashed line

(unconnected) to a solid black line (supposedly connected). Although we usually

get great CO2 waveform tracings, we found many code summaries with snapshot

strips showing a solid, perfectly straight flat black line at zero. At

first, we reviewed these with other EM and EMS physicians, anesthesiologists,

and

company personnel—most of whom said “misplaced tube, should have been

pulled.

†Good paramedics were adamant that the tube was well placed, though, and

then we had runs where the tracing went from solid flat line at zero to good

waveform (or vice versa) with no intervention done—then saw a couple patients

resuscitated while the CO2 line was still flat at zero, and then runs where

the LP 12 showed zero but a colorimetric or bar graph ETCO2 device showed

great readings. And what true biological reading is ever absolutely flat??

Turns out that as the filterline is being screwed in, tracing goes from dashed

line to solid, but if not 100% connected, the solid line stays straight at zero

(is NOT sensing patient’s CO2). Screw the sensor in a hair more, and tiny

waveform appears (very low plateau). Screw it in the rest of the way and the

waveform reaches its full, real height. Actual ETCO2 # shone on device may or

may not be of help. During cardiac arrest (e.g., post defib or if moving

patient), it’s easy for the filterline to unscrew a little bit, and tracing

changes to flat line—as a paramedic from another system pointed out, the

sensor

line comes coiled in a package, and coil effect in the plastic makes it twist

outward. Please go to the link below for slides showing this.

Troubleshooting tips for LP12 ETCO2 use with intubations:

* Hand-straighten the tubing before it is connected to patient or

monitor (takes out coils)

* Be sure to tighten fully when first connecting the CO2 sensor line

to the LP

* When fully tight, the “wings†on the connector should be perfectly

horizontal (confirmed by PhysioControl engineer)

* If a solid but straight black line at zero appears (no waveform),

immediately tighten the connection and recheck waveform tracing and the

numerical ETCO2 reading

* If line is still straight, recheck patient and tube immediately—

reconfirm tube placement carefully by all clinical means, including looking

again

with laryngoscope to see tube going thru cords; recheck that good CPR is

being done. If tube is confirmed by other means, use it and DOCUMENT well. If

any doubt remains, then replace tube.

Also, if a solid straight flat black line at any higher number suddenly

appears on the tracing, try checking connection and then replace with new

sensor,

but this is most likely due to the pump (inside device) shutting off because

liquid entered the device (not yet confirmed by Physio). Device does not

tell user if pump shuts off, but when pump shuts off the screen tracing just

stays up at whatever height it was just at, and shows a solid straight line

(confirmed by Physio). It might stay that way until drying out hours later, or

being serviced.

Am happy to answer any questions. And I’ve apologized to my paramedics

wrongly told by me that they misplaced an ETT!!

Kathy Schrank, MD, FACEP

EMS Medical Director, City of Miami Fire Rescue

UM/JMH Emergency Medicine

kschrank@...

_http://www.acep.org/workarea/downloadasset.aspx?id=38120_

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