Добавил:
Sekretar
kiopkiopkiop18@yandex.ru
t.me/Prokururor I Вовсе не секретарь, но почту проверяю
Опубликованный материал нарушает ваши авторские права? Сообщите нам.
Вуз:
Предмет:
Файл:Ординатура / Хирургия / Библиотека им академика М.И. Перельмана / Книга_4510_Библиотеки_им_академика_М_И_Перельмана.pdf
346
X
Fig. 10 Bougie loaded
tube, prepared for
intubation
Fig. 11 Laryngeal mask
in place
R. Lima et al.
UVULA
PHARYNX
HYPOPHARYN
EPIGLOTTIS
LARYNX
TRACHEA
ESOPHAGUS
Laryngeal Mask
The laryngeal mask airway (LMA) was initially designed as a method to allow more
effective ventilation and reduce the morbidity related to tracheal intubation.
However, it had an important clinical impact and since 1995 has been included in
difcult-airway algorithms. LMAs consist of a tube attached to a pneumatic cushion, which adapts to the supraglottic structures (Fig.11). It is inserted blindly, and
the quality of the ventilation is tested afterward. The provider needs to bag and carefully seek air leaks that will compromise ventilation.
Several models are available (Fig.12). Second-generation devices incorporate
recent improvements such as a gastric aspiration channel, an integrated bite block,
and the ability to tolerate increased ventilatory pressure. Some studies suggest abandoning the use of rst-generation models and adoption of second-generation versions as the rst-choice LMAs [20].
Compared with endotracheal intubation, the LMA allows greater hemodynamic
stability, less alteration of intracranial and intraocular pressure, and lower incidence of cough and pharyngeal pain. The basic skills for insertion of the laryngeal
mask are acquired more rapidly than those of face mask ventilation or direct laryngoscopy [21–23].
Dicult Intubation: How toAvoid aTracheostomy
347
a
b
c
d
e
f
i
g
h
jk
l m
Fig. 12 Main commercially available laryngeal masks. First-generation: (a) LMA Classic, (b)
LMA Flexible, (c) LM Solus, (d) LM Portex Soft Seal, (e) LM AuraOnce, (f) Air-Q intubating
laryngeal airway, (g) LMA Fastrach, (h) LM Aura-i. Second-generation: (i) ProSeal LMA, (j)
Supreme LMA, (k) AuraGain LM, (l) i-gel, (m) Baska mask
348
ab
R. Lima et al.
Insertion Technique
Several techniques for insertion of the laryngeal mask have been described; the
most popular was described by its inventor, Archie Brain (Fig.13). The size of the
mask should be chosen according to the patient’s weight (Table2).
When correctly positioned, the mask surrounds the larynx and its distal tip is
located in the upper esophageal sphincter. An adequate anesthetic depth should be
obtained before attempting insertion, to avoid reexes such as coughing, choking,
laryngospasm, or even biting the nger of the provider. The technique is to slide the
device along the soft palate and posterior wall of the pharynx, guiding with the nger, until an increase in resistance is observed. At this time, the mask is inated,
with a pressure of not more than 60cm H
cuit. There may be a slight retrocession of the mask with insufation, which indicates correct positioning. The adaptation of the mask is initially tested with light
O, and is coupled to the ventilation cir-
2
cd
Fig. 13 Classic technique for insertion of a laryngeal mask device. With the neck exed and the
head extended by pushing the head from behind with one hand, the laryngeal mask airway (LMA)
is inserted into the mouth with the other hand(a). The inserting hand is positioned like a pen, with
the index nger placed at the junction of the cuff and the tube. The LMA tip is pushed up against
the hard palate after verication that it is lying at against the palate and that the tip is not folded
over. Using the index nger, the mask is pushed into the patient’s mouth, still maintaining pressure
against the palate(b). As the mask moves in, the index nger maintains pressure against the posterior pharyngeal wall to avoid the epiglottis(c). The index nger is fully inside the mouth at the
end of insertion(d). The other hand holds the LMA while the inserting nger is removed from the
mouth. The cuff is inated without holding the tube, permitting the device to position itself
correctly
Dicult Intubation: How toAvoid aTracheostomy
Table 2 Laryngeal mask size according to patient weight
Laryngeal mask size
1 Infants <5
1.5 Infants 5–10
2 Children 10–20
2.5 Children 20–30
3 Children and young adults 30–50
4 Adults 50–70
5 Adults >70
Patient
Weight (kg)
349
manual ventilation by observing the thoracic expansion, in addition to hearing
sounds that indicate a leak or obstruction to the passage of air. Second-generation
masks support airway pressures up to 37cm H2O [24].
Difculties of insertion occur in up to 4.5% of cases. Head extension, protrusion of the mandible, and tongue traction may help. Factors that impair the efciency of laryngeal mask ventilation include inadequate positioning, increased
airway resistance, and reduced lung compliance. In the event of ineffective ventilation, one can attempt to reinsert the same mask or one of a different size. Small
leaks that do not compromise ventilation can be tolerated, especially in emergency situations.
Role oftheLaryngeal Mask Airway inAirway Management
The LMA is used in several clinical situations and has proved very useful in airway
management. It has played an important role in difcult-airway algorithms, especially in “cannot intubate, cannot ventilate” situations. The main issues are that,
even when well tted, it does not provide a reliable airway seal and it is not recommended for long-term mechanical ventilation. In these cases, it acts as a rescue
device until the patient can be awakened and intubated or, if necessary, a surgical
airway can be obtained.
LMAs may be used to facilitate tracheal intubation, and the typical scenario in
which this technique is useful is when an LMA has been placed as a rescue device
due to failed direct laryngoscopy or failed intubation. It may be used for blind or
beroptic bronchoscope-guided methods to aid intubation. A specic advantage of
this technique is the ability to continue ventilating and anesthetizing the patient
through the LMA until a conventional endotracheal intubation is performed. It is
advisable to use beroptic bronchoscope-guided techniques to ensure greater success of tracheal intubation through an LMA.
Complications andContraindications
The LMA offers less protection than the endotracheal tube against gastric aspiration. These devices are not recommended for patients at greater risk for
350
Fig. 14 Combitube in place
R. Lima et al.
regurgitation or vomiting. Device failure related to inadequate ventilation is more
likely to occur in patients with increased intrathoracic pressures, such as those
with obesity or obstructive airway disease. Traumatic injuries can happen if positioning proves to be challenging, and upper airway bleeding and swelling can
degenerate into a “cannot intubate, cannot ventilate” situation. In fact, a sore
throat is a common complication after multiple placement attempts or if high cuff
pressure is used.
Other Supraglottic Devices
Other less used supraglottic devices are available, including the Combitube and the
laryngeal tube. The Combitube consists of a double-lumen tube with two cuffs. The
insufation of the distal cuff seals the esophagus while the proximal cuff closes the
oropharynx. Its insertion is performed blindly, allowing adequate ventilation
whether it is positioned in the esophagus or in the larynx (Fig.14). It has been used
in prehospital care.
The laryngeal tube is a single-lumen device in which both cuffs are insufated
from a single ination line. Holes in the tube between the proximal seal and the
distal cuffs deliver the fresh gas mixture to the laryngopharynx. Placement is rapid
and it has been successfully used in “cannot intubate, cannot ventilate” situations
and in LMA failure.
Dicult Intubation: How toAvoid aTracheostomy
351
Videolaryngoscopes
Advances in beroptic and video technologies have led to the development of devices
that facilitate the indirect visualization of the larynx, with minimal mouth opening
and head extension. The indirect image of the larynx by these devices can be obtained
in two ways: (1)through a beroptic bundle or a system of prisms to a lens or a video
system; or (2)through a video camera that transmits a digital image to a display. The
display can be integrated into the device or used as a stand-alone monitor.
The various models have different blade designs: (1)a traditional blade; (2) a
nonchanneled angulated blade; or (3)a channeled angulated blade. The traditional
blade devices are inserted using the direct laryngoscopy technique, while the other
two designs require a slightly different technique. The blade is introduced on the
midline of the oral cavity until its tip reaches the vallecula. The tongue can be pulled
to facilitate the insertion of the blade. There is no need for the snifng position,
which is advantageous in patients with cervical spine injuries or limited neck extension. When in place, the blade can be pulled up for further view improvement. The
nonchanneled blades require a stylet with a “hockey stick” curvature to be used to
guide the tube. Once the blade is positioned, the next step is placing the tip of the
tube in the oropharynx under direct visualization. Failure to do so can lead to accidental tearing or perforation of the tonsil pillars, causing profuse bleeding. The
channeled blades have a more bulky structure which can hinder their insertion into
small-opening mouths. In a simulated difcult-airway scenario (patients with a cervical collar), nonchanneled devices had a higher rate of successful airway management in the rst attempt [25]. Glottic visualization does not always equate to
successful endotracheal intubation.
Videolaryngoscopes have not been used only in emergency difcult-airway situations but also in routine airway management [26], as they allow a higher probability of successful intubations in unexpectedly difcult airways. This probability can
range from 94% to 99% [27, 28]. Some authors have advocated the use of videolaryngoscopes as the new standard of care [29]. We do not suggest routine use of videolaryngoscopes, since it may lead to loss of the skills required for direct laryngoscopy.
Videolaryngoscopes are not fail proof. The presence of secretion or blood in the
upper airway may hinder the use of these devices. Failure to perform an optimal
direct laryngoscopy prevents correct evaluation of patients, increasing the frequency
of unsuccessful intubations. Insisting on direct laryngoscopy, however, can be
harmful, since multiple attempts can lead to airway trauma and edema, making
ventilation impossible. In these cases, videolaryngoscopy is highly recommended.
We comment below on some of the commonly used devices.
Truview
The Truview (Truphatek, Netanya, Israel) can be considered a rst-generation videolaryngoscope. It resembles a common laryngoscope with a handle and a Macintoshdesign blade. The blade, however, contains a lens that allows a 45-degree view at its
352
Eye piece
ab
R. Lima et al.
Optical view tube
Tm
Fibre Clip
Oxygen Port
Fig. 15 Truview videolaryngoscope. (a) Truview handle and blades. (b) True view angle of view.
Reproduced under Creative Commons Attribution License from [30]
Light Guide
View tube
distal end
Blade distal tip
A. Tip of blade
B. Line of sight
C. Prism edge
42±2º
B
A
C
tip (Fig.15). The eyepiece of the lens can be connected to a video camera, but it can
also be used without electronic equipment. It has the advantage of being more
robust, with less chance of trouble because of electronic malfunction. The Truview
can be used in patients with very small mouth openings. A bougie or a tube stylet is
needed to guide the tube [30].
GlideScope
The GlideScope (Verathon, Seattle, WA, USA) is a exible camera that is introduced into a plastic nonchanneled blade (Fig.16). It has a high-resolution display,
which can record the procedure. It is recommended to load the tube with a stylet
matching the angulated prole of the blade.
C-MAC
The C-MAC (Karl Stortz, Tuttlingen, Germany) has a traditional blade design. A
more angulated blade (D-blade) has been released recently, for more difcult intubation situations (Fig.17). It has a display that is connected to the handle by a cable.
The newer models have an integrated display at the handle, which facilitates operator use.
Dicult Intubation: How toAvoid aTracheostomy
Fig. 16 GlideScope
videolaryngoscope
353
Fig. 17 C-MAC videolaryngoscope
354
R. Lima et al.
McGrath
The McGrath (Aircraft Medical, Edinburgh, UK) has a traditional blade design, which
allows direct or indirect laryngoscopy, by an integrated display. It has a narrower and
more delicate blade, which facilitates intubation in patients with small mouths (Fig.18).
King Vision
The King Vision (King Systems, Noblesville, IN, USA) has the advantage of offering two styles of blades: it can be used with nonchanneled or channeled angled
blades. It has an integrated display (Fig.19). The nonchanneled blade is easier to
insert but requires the use of a stylet or bougie.
Fig. 18 McGrath videolaryngoscope
Dicult Intubation: How toAvoid aTracheostomy
Fig. 19 King Vision
videolaryngoscope
355
VividTrac
The VividTrac (Vivid Medical, Palo Alto, CA, USA) is a channeled angled-blade
device. It has a USB cable, which plugs into a mobile or tablet device (Fig.20). It
has a low price compared to other videolaryngoscopes. It offers great visualisualization because it uses the full HD screen of the device (cellphone, tablet or computer).
Airtraq
The Airtraq SP (Prodol Meditec SA, Gueco, Spain) is a channeled angled-blade
device, which has an integrated display (Fig.21). It can also be used through direct
visualization, which avoids the need for electronic components and can even be
used in magnetic resonance rooms. It has a rapid learning curve and greater chance
of successful airway management than direct laryngoscopy [31].
Fiberoptic Bronchoscope
The beroptic bronchoscope is the last-resort device for management of difcult
airways but has some limitations. It consists of a exible insertion cord with a working channel built in, bers that conduct the light to the tip, and bers that provide