In
this clinical investigation, including 248 adult patients with
a wide range of conventional laryngoscopic views requiring
orotracheal intubation for elective thyroid surgery, tracheal
intubation with the Airtraq Optical Laryngoscope (AOL) performed by novice but instructed users was successful at the first attempt in 97 percent with
successful tracheal intubation after a maximum of two attempts
in all patients. These favorable results may not be obtained when
operators without formal instruction in the technique perform tracheal intubation attempts
with the AOL.
The results of our study strongly support the initial use
of a suitable airway model for formal hands-on training;
this approach was obviously the key factor for success. When the
novice users of the AOL performed the first series of
laryngoscopy and tracheal intubation attempts on patients, they
were already familiar and confident with the technique. The
number for obtaining acceptable clinical performance and
competence with this device, estimated by the instructor,
remained within 10 applications for all operators. The clip-on
AOL Video System instead of the removable rubber coat on the
view finder allows
viewing of the entire procedure on a compatible medical monitor, not
used in this study; simultaneous viewing by the operator and
the instructor might have even accelerated the instruction.
The relatively bulky AOL blade, a limitation of this device, may impede blade insertion,
particularly in patients with limited mouth opening and/or
restricted pharyngeal space (encountered in 10 percent). However,
the AOL
blade favorably incorportes the tracheal tube (TT) already in
the tube-guide channel, eliminating the need for additional
space passing the TT through the oral cavity.
The view finder of the AOL allowed visualization of anatomical
structures with adequate image quality and provided a panoramic
view of the laryngeal aperture when the blade was properly
inserted. There were no problems with poor visibility due to
fogging of the optical system by warming-up the system
slightly above body temperature within a short period of time, a
special feature of the AOL;
also secretions did not appear to interfere with the laryngeal
views because the optical system is protected and remote from the
tip of the blade.
Visualization of the entire laryngeal aperture,
a prerequisite of successful AOL-assisted tracheal intubation,
failed in only one patient at the first attempt but was finally obtained
at the second attempt. The curvature of the tube-guide channel and the orientation of
the optical system of the AOL were usually well aligned with the
laryngeal aperture; when the laryngeal aperture was in the center
of the view finder, advancement of the TT into a midtracheal
position was generally successful at the first attempt, except
in 6 patients. Nevertheless, there were minor problems and
difficulties with impeded TT passage through the laryngeal
aperture in 10 percent, partly attributable to distortion of the
larynx, frequently observed in patients undergoing thyroid
surgery. When the TT impinged on laryngeal structures, usually on the arytenoid cartilages or the interarytenoid area, a backward, upward, and to the left or right movement of the AOL
blade regularly solved this problem. Interestingly, impeded TT
advancement during tracheal passage despite tracheal deviations
and/or compressions by enlarged thyroid glands and using
standard TTs was rarely a
problem.
Severe complaints and injuries associated with airway management were not
observed; this may be due to vizualization of the entire
laryngeal aperture during successful laryngoscopy and controlled TT advancement into a
midtracheal position. Conventional tracheal intubation, particularly after multiple
attempts, may not provide comparable results. It should be noted,
that the insertion of the AOL blade into the oral cavity was
performed with special caution because this maneuver is usually
blind; pharyngeal injuries by uncontrolled blade insertion
cannot be excluded.
The efficacy of the AOL in difficult CL situations is now supported also by other clinical studies. Maharaj and co-workers (3) compared the ease of
tracheal intubation with the AOL or the Macintosh laryngoscope
(ML) in patients with normal airways but with manual cervical
spine immobilization in a randomized, controlled study
(with 20 patients in both groups). All patients, except one
patient in the ML group requiring three attempts, were
successfully intubated at the first attempt; the AOL reduced
the duration of the intubation time and the need for additional
airway maneuvers. Furthermore, they compared the success of tracheal intubation with
the AOL or the ML in patients with anticipated difficult
CL (again with 20 patients in both groups) (4).
AOL-assisted tracheal intubation was successful in all patients
after a maximum of two attempts (in 19 patients at the first
attempt); even after three attempts, conventional tracheal
intubation failed in 20 percent, but these 4 patients were
successfully intubated with the AOL at the first attempt.
Favorable results were also published by Ndoko and co-workers (11),
comparing the success rate of tracheal intubation with the AOL
or the ML at the first attempt in morbidly obese patients (with
53 patients in both groups). Tracheal intubation with the AOL
and the ML was successful in 100 and 89 percent, respectively;
the 6 patients with unsuccessful ML-assisted tracheal intubation
were successfully intubated with the AOL at the first attempt. Obese patients were given preferentional enrollment
into our study; we also had less problems with successful
tracheal intubation in this patient population.
In a case
series of 7 patients with difficult CL (grade 5, visualization of only the soft palate,
despite external laryngeal manipulation) and failed tracheal
intubation after multiple attempts with CL, Maharaj and co-workers (7) were sussessful at the
first attempt of AOL-assisted tracheal intubation with views
of the entire laryngeal aperture. We agree with their
suggestion, that the AOL may
serve as valuable rescue device in situations of difficult CL and failed tracheal intubation.
Provided formal instruction, the success of AOL-assisted
orotracheal
intubation performed by novice users was not affected by
conventional laryngoscopic view grading. The AOL proved
to be uniquely useful for routine and difficult laryngoscopy and
tracheal intubation in clinical practice. The AOL may be also
useful in medical emergency situations, but this suggestion has
to be supported by further studies.