Second, although this study showed the efficacy of a
pharyngeal cannula during procedural sedation, the fact
that the pharyngeal cannula administers dry gases directly
to the pharynx may be a problem. No humidifying devices
(such as a bubble humidifier) was used in this study be-
cause those devices might not commonly be used in upper
gastrointestinal endoscopy patients. Dry-gas administra-
tion can cause airway complications, such as ciliary dys-
function, airway injury, atelectasis, and pneumonia.
12-14 A
pharyngeal cannula may be slightly more invasive than a
nasal cannula, and local adverse effects have not been
evaluated. Hence, clinical evaluation is necessary to con-
firm the safety of oxygen administration via a pharyngeal
cannula and the necessity of humidifying devices. The
fraction of expired oxygen might affect the FIO2
, but it was
not measured in this study.
Another limitation of this study is that the mannequin
breathed via both mouth and nose in open-mouth settings.
In contrast, patients can breathe through their noses or
mouths with their mouths open. We did not study the
situation in which the mannequin breathed only through
the mouth because it is inappropriate to evaluate the effect
of oxygen supplementation via a nasal or pharyngeal can-
nula in such a setting.
Conclusions
A pharyngeal cannula provided a higher FIO2
than a
nasal cannula at the same oxygen flow during open- and
closed-mouth breathing in this study. Oxygen adminis-
tration via a pharyngeal cannula rather than a nasal
cannula might be clinically useful in sedated patients,
who are likely to need a higher FIO2
to prevent severe
hypoxia. The breathing pattern did not influence the
FIO2
in this study