In this study, we found that a pharyngeal cannula provided
a higher FIOi than a nasal cannula at the same oxygen
flow during both open- and closed-mouth breathing.
Compared with a nasal cannula, oxygen was delivered
close to the trachea with a pharyngeal cannula, thus minimizing
dilution of the oxygen with air. Eastwood et al9
reported that nasopharyngeal oxygen supplementation via
a 10 French catheter inserted just behind the soft palate
required a lower oxygen flow compared with a face mask
to maintain oxygen saturation. Transtracheal catheters were
also reported to be more effective than nasal cannulas at
the same oxygen flow in a previous study