Module 14
Advanced Airway Techniques
Part 2 - New Generation Supraglottic Ventilatory Devices
Desirable Features and Optimal Methods for Testing
DESIRABLE FEATURES OF SUPRAGLOTTIC AIRWAYS - con't
First time insertion success
should be high and require a minimum of manipulations. With
current devices, first time insertion success ranges from below
70% to above 95%. The average number of manipulations required
to enable insertion ranges widely, from less than 1 manipulation
in 25 cases to more than one per case.
The anesthesiologist requires an
airway that, once inserted, does not require airway
manipulations or repositioning during anesthesia, enabling
‘hands-free’ anesthesia. The most functional devices require an
intervention in less than 1 in 25 cases while others require
intervention in two thirds of cases.
The airway should be stable when
head and neck position varies, such as during rotation to
improve surgical access, or when the head and neck are
repositioned for further procedures. Limited evidence suggests
the stability of different supraglottic airways devices under
these circumstances is variable.
Intraoperative complications
(e.g., airway obstruction, loss of airway, regurgitation,
laryngospasm) should be infrequent. The published incidence of
minor complications with existing devices ranges 6-fold from
less than 10 to 60%. Serious and minor repetitive
complications, or the need to perform repeated or continuous
manipulations to maintain the airway, may force early removal of
the airway. This is the ultimate failure of the airway device,
and occurs with an incidence of less than 1 in 50 cases to more
than 1 in 5 cases.
The ideal supraglottic airway is
reliable for both spontaneous and controlled ventilation. Of
the existing devices, several versions of one device function
poorly during spontaneous ventilation and another is designed
specifically to facilitate controlled, rather than spontaneous
ventilation. Several devices, which produce low-pressure seal
with the airway, may be unsuitable during controlled ventilation
because of the risk of gastric inflation and regurgitation risk.
Protection of the airway from
aspiration is critically important. Supraglottic airways are
increasingly used in more obese patients, those with minor
gastroesophageal reflux and during controlled ventilation.
Several of the newer devices have features that lessen the
likelihood of gastric inflation and enable access to the
esophagus / stomach to drain the stomach or enable venting of
regurgitated matter. For some of these devices, there is
experimental and clinical evidence to support the function of
these innovations, while for other similar devices there is
none. Regurgitation and aspiration are infrequent events.
Evidence proving better safety of one device compared with
another could come only from studies of several million
patients. Such studies are impractical. Instead, safety data
has to be acquired by analyzing the design features, surrogate
measures of airway safety, and bench models. Supraglottic
airways are also used for nasal and oropharyngeal surgery, yet
only a few have been demonstrated to protect of the airway from
pharyngeal secretions. It remains unclear which of the newer
devices are safe for such operations.
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