Does Nasal Cannula Design Affect Function?
R. Eleanor Anderson, MD, Calvin A. Brown, III, MD, FAAEM
A crossover comparison of four nasal cannulae shows differences in oxygen delivery and ETCO2
To assess whether the design of nasal cannulae influences O2 delivery and detection of end tidal carbon dioxide (ETCO2), researchers enrolled 45 healthy adults in a randomized, crossover study of four different nasal cannulae: bifurcated nasal prongs with both O2 delivery and CO2 sensing in each prong (Hudson), separate nasal prongs for O2 delivery and CO2 sensing (Salter), and nasal prongs with CO2 sensing only and cloud delivery of O2 via either multi-vents (Oridion) or dual vents (Medline). ETCO2 and oxygen delivery (assessed by pharyngeal oxygen percentage and arterial blood gases) were measured for 2 minutes on room air and during supplemental O2 delivery at 2, 4, and 6 liters per minute. The study was funded by the manufacturer of the Salter device.
At higher flow rates, oxygen delivery via prongs was associated with higher pharyngeal O2 percentage and PaO2 than cloud delivery via vents; for example, at a rate of 6 L per minute, pharyngeal O2 percentage was 49.8% with delivery via separate prongs vs. 36.2% with cloud delivery via multi-vents. Mean PaCO2 did not differ significantly with type of nasal cannula or flow rate, averaging 39–40 mm Hg across all devices and flow rates. ETCO2 was significantly lower with bifurcated prongs than with the other three designs, with errant CO2 tracings at higher rates of supplemental O2 delivery.
The optimal nasal cannula design allows both effective O2 delivery and ETCO2 measurement. This small study suggests that bifurcated (septated) prongs may impede proper CO2 detection and that cloud oxygen delivery is inferior to prong delivery. Until more information is available, nasal cannula with these design elements should be avoided when alternatives are available.
Ebert TJ et al. The effectiveness of oxygen delivery and reliability of carbon dioxide waveforms: a crossover comparison of 4 nasal cannulae. Anesth Analg 2014 Nov 11 [e-pub ahead of print]. (http://dx.doi.org/10.1213/ANE.0000000000000537)
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