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A modified CO2/O2 Guedel airway improves capnographic accuracy compared with a CO2/O2 nasal cannula

An infant manikin study

Moll, Jens; Anagnostopoulou, Pinelopi; Frei, Franz J.; Erb, Thomas O.

European Journal of Anaesthesiology (EJA): August 2018 - Volume 35 - Issue 8 - p 566–572
doi: 10.1097/EJA.0000000000000818
Paediatric anaesthesia

BACKGROUND Capnography via a CO2/O2 nasal cannula is commonly used for respiratory monitoring during sedation. However, signal disturbances are frequently encountered, especially in young children.

OBJECTIVE Sampling ports placed closer to the trachea have been shown to result in improved signal quality. In a manikin model of a 6-month-old infant we compared capnography from a modified Guedel airway with a CO2 port located at the tip with that from a CO2/O2 nasal cannula.

DESIGN A comparison study using an artificial model of a breathing 6-month-old infant.

SETTING Department of Paediatrics, Inselspital Bern, Switzerland, from March 2016 to June 2016.

MATERIAL Modified CO2/O2 Guedel airway.

INTERVENTIONS Capnography using a modified CO2/O2 Guedel airway or a CO2/O2 nasal cannula was performed for tidal volumes of 20 to 80 ml (in steps of 20 ml), respiratory rates of 20 to 60 min−1 (in steps of 10 min−1) and with different O2 flows (0 to 2 l min−1, in steps of 0.5 l).

MAIN OUTCOME MEASURES Comparison of differences between tracheal and device CO2. Secondary outcomes included the effect of various respiratory settings and O2 flows on the CO2 difference.

RESULTS The tracheal to device CO2 difference was significantly smaller when using a modified CO2/O2 Guedel airway vs. a CO2/O2 nasal cannula: Mean ± SD, 16.8 ± 4.9 vs. 24.1 ± 5.9 mmHg, P less than 0.0001. An O2 flow of 0.5 to 2 l min−1 did not influence the tracheal to device CO2 difference with the modified CO2/O2 Guedel airway in contrast to the CO2/O2 nasal cannula where there were significant differences (P < 0.0001). The effect of various tidal volumes and respiratory rates proved to be similar in both devices.

CONCLUSION Capnography traces derived from a sample port at the tip of a modified CO2/O2 Guedel airway were more accurate than those obtained from a CO2/O2 nasal cannula.


From the Department of Anesthesiology, University of Basel, University Children's Hospital Basel, Basel (JM, FJF, TOE) and Department of Paediatrics, Pediatric Respiratory Medicine, Inselspital, University of Bern, Bern University Hospital, Bern, Switzerland (PA)

Correspondence to Jens Moll, Department of Anaesthesiology, University of Basel Children's Hospital, Spitalstrasse 33, PO Box CH-4056, Basel, Switzerland Tel: +41 61 704 28 27; e-mail:

Published online 30 April 2018

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© 2018 European Society of Anaesthesiology