Transcutaneous CO2 vs endtidal CO2

[susanyoung]

Hello all,
We are having a discussion about the benefits and deficits of using non-invasive CO2 monitoring in our NICU population. We have rented a transcutaneous CO2 monitor, but have not had great luck getting readings the clinicians can trust. We are preparing to get the end tidal software for our Servo i vents. I feel that both monitoring modalities have their good and bad points, such as the end tidal not being useful when an infant is receiving HFOV, and the transcutaneous not working well for an infant with gneralized edema. Does anyone care to comment on their unit's use of either one of these noninvasive methods of monitoring CO2? We have the Sentec CO2 monitor and have had trouble with the membrane integrity, and I think that the clinican discomfort with the machine resulted in a less than impressive trial. Any anecdotal comments are welcome, as well as any references to supportive or descriptive information.
Thanks,
Susan

[JACK]

Check out these three articles:

1) Tingay DG, Stewart MJ, Morley CJ. Monitoring of end tidal carbon dioxide and transcutaneous carbon dioxide during neonatal transport. Arch. Dis. Child. Fetal Neonatal Ed. 2005 Nov 1;90(6):F523-526.
LINK (http://fn.bmj.com/cgi/content/full/90/6/F523)

2) Molloy EJ, Deakins K. Are carbon dioxide detectors useful in neonates? Arch. Dis. Child. Fetal Neonatal Ed. 2006 Jul 1;91(4):F295-298.
LINK (http://fn.bmj.com/cgi/content/full/91/4/F295)

3) Evaluation of a new combined transcutaneous measurement of PCO2/pulse oximetry oxygen saturation ear sensor in newborn patients.
Pediatrics. 2005 Jan;115(1):e64-8. Epub 2004 Dec 15.
LINK (http://pediatrics.aappublications.org/cgi/content/full/115/1/e64)

[Skysurfer]

Hello Susan,

we are using the Radiometer MicroGas 7650 for all our children on vents or assisted ventilation (e.g. NCPAP). It´s a great device, if one is aware of it´s limitations...

BROMLEY I.; Transcutaneous monitoring - understanding the principles, Infant, 4(3):95-98, 2008 gives a good overview (from a nursing perspective)

In the neonatal population, one simply can´t use the EtCO2 devices. Neither the sidestream nor the mainstream devices are capable of providing reliable values in the NICU population. That is simply because in this population the tidal volumes aren´t big enough and the respiratory rates are usually too high to allow the baby to generate an end expiratory tidal plateau, which in turn almost reflects the alveolar PCO2.
Healthy newborn (term) children may generate enough tidal volume at normal respiratory rates, but most children in the NICU are preemies or sick term born children which have decreased tidal volumes and/or are tachypneic, which further decreases the tidal volumes...
Another thing is the handling of such devices. They are simply all heavy, are generating too much dead space and are bulky!

HARIGOPAL S., SATISH H.P.; End-tidal carbon dioxide monitoring in neonates, Infant, 4(2): 51-53, 2008 provides an overview (again from a nursing perspective)

The sidestream technology is tricky, because it needs/aspirates 50ml/min (Microstream) of gas from the circuit to function properly, which limits it´s use to the pediatric population. We recently bought such a device for our new transport incubator and weren´t able to use it without problems, so far.

As i said before, we are happy with our TcCO2 monitor. We decreased the heat to 43°C and found no skin burns so far, even with the smallest preemies and if you remind yourself from time to time, that the device only represents the values under the skin surface and that this is the reason why it simply not always correlates with CO2 values in the blood, it´s a safe thing.

Some people are arguing that the CO2 monitoring is overvalued because with the new ventilation modes one can choose "the right" tidal volume and respiratory rate and with stable conditions arterial blood gases should be enough.

i hope that helps

Cheers Norbert

[Stefan Johansson]

I would like to add another argument for Tc-monitoring...
can be used for CO2-monitoring during nCPAP.