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 (in steps of 10 min) and with different O2 flows (0 to 2 l min, 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 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.
Trial registration: Not applicable.