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“I Can’t Ventilate!” Intraoperative
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Anesthesia Safety Events andAirway
18
Management
MarwanSarkisRizk, SaradaEleswarpu,
andChakibMauriceAyoub
Introduction
Airway catastrophes and hypoxia have been identied as the leading causes of neurological injury and death during anesthesia or resuscitation. In the American
Society of Anesthesiology Closed Claims Analysis, failure to oxygenate patients
with respiratory failure was associated with major morbidity and mortality [1].
Difcult airway management (DAM) is important and critical.
For its latest practice guidelines, the American Society of Anesthesiologists
denes a difcult airway as “a clinical situation in which a conventionally trained
anesthesiologist experiences difculty with face mask ventilation of the upper airway, difculty with tracheal intubation, or both” [2]. Planning and preparedness in
these situations can save lives, and there is advocacy for an algorithm-based strategy. Many international bodies such as the American Society of Anesthesiologists,
European Resuscitation Council, and Difcult Airway Society have developed recommendations and algorithms that facilitate a basic pathway for the management of
difcult airway.
It is crucial that all stakeholders involved in patient airway management be
familiar with the techniques and tools needed to provide adequate oxygenation [3].
The literature provides insights into the various types of protocols, advanced airway
devices [4, 5], and availability of such equipment in different countries [6, 7]. The
important role of simulators to acquire and maintain skills in difcult airway management is also widely established [8]. This chapter focuses on the organization of
resource and staff during catastrophic airway situations.
M. S. Rizk (*)
Department of Anesthesiology, American University of Beirut, Beirut, Lebanon
e-mail: mr04@aub.edu.lb
S. Eleswarpu · C. M. Ayoub
Department of Anesthesiology, Duke University school of Medicine, Durham, NC, USA
© Springer Nature Switzerland AG 2024
J. J. Hoballah et al. (eds.), Principles of Perioperative Safety and Efciency,
https://doi.org/10.1007/978-3-031-41089-5_18
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M. S. Rizk et al.
Difficult Airway Management (DAM): Key Factors
Current clinical practices based on established guidelines emphasize airway evaluation, basic preparation, and algorithm-based strategies for intubation. Respiratory
failure can be caused by many reasons, and it is important that non-patient factors
are also acknowledged. If not addressed, these factors can present a risk that could
complicate airway management and threaten patient safety [9, 10].
“Complexity factors”—a term that is commonly used to describe factors contributing to the complexity of a procedure and includes experience, time pressure, available equipment, position, location, and human factors—should be identied and
considered [11]. In the context of difcult airway, complexity factors encompass
one or more of the following adverse outcomes: failures in technique and equipment; wrong head position; side effects of certain drugs; and pathological airway
obstruction.
The possibility of difcult airway occurring is a risk if underlying causes that
are contributing factors are not addressed. For example, obstructive sleep apnea
patients constitute a recurring risk unless the pharyngeal pathology is corrected
[12]. The depth of anesthesia can also play a signicant role in precipitating a difcult airway scenario or securing a safe airway; laryngeal spasm due to light
anesthesia may result in difcult mask ventilation (DMV), while adequate anesthesia depth will likely result in easy mask ventilation (MV) [13]. “Composite
failure” of airway management is another prominent observation from previous
studies: a phenomenon in which if one airway management technique is difcult
or fails, the chance of alternative techniques being difcult or failing is signicantly higher [14].
Emergency Conditions
Airway management is sensitive to both context and time; it is inuenced by the
clinical condition of the patient, physician expertise, urgency of the situation, and
the environment in which the procedure takes place [15].
Intubating conditions uctuate with changes in the clinical picture as well as
environmental context. For example, a patient who is known to be an easy intubation may become “difcult” when presenting in septic shock with a low oxygen saturation to a remote hospital that has limited resources. If this same patient
was in an intensive care unit in a busy metropolitan hospital, the availability of
more resources and experienced providers would inuence the approach to this
patient’s airway management. While preparing for a challenging intubation, the
most experienced provider should be performing the intubation to minimize
adverse events. The clinical picture can also evolve, often due to factors including time delay, worsening of the disease pathology, or tiring out after a period of
increased work of breathing. For example, a patient with an epiglottitis may be
able to protect the native airway upon initial presentation to a hospital; over time,
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the patient may become tired due to a period of increased work of breathing and
may require immediate establishment of a secured airway. It is the responsibility
of the anesthesiologist to continuously monitor patients and readjust the strategy
accordingly.
A pitfall to avoid during a challenging difcult airway situation is “plan continuation error,” which is a validated detrimental factor in aviation crashes [16]. The
initial airway management plan, seemingly clear and rock solid in the beginning,
could prove inapplicable as the circumstances change. For example, if a tumor starts
bleeding during intubation, the view of a video laryngoscope or ber-optic bronchoscope will be obscured and the physician may have to use another device that does
not rely on a camera for securing the airway. It is crucial that the physician does not
ignore the warning signs and adapts his or her strategy to the changing dynamics of
the situation to avoid adverse events. Experience and training raise awareness of
plan continuation error and avert any potential hazards.
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Operator Conditions
Mask ventilation (MV) is a basic technique for providing oxygenation before intubation. Prompt diagnosis of difcult mask ventilation (DMV) could maximize risk
management strategy and avoid catastrophic complications. Most operators rely on
their subjective assessments such as thoracic movement and resistance of the anesthetic bag. In the literature, DMV is interpreted as inadequate mask seal, increased
airway resistance, and decreased respiratory compliance. Clinical skills can be
taught to address difculties in each of these categories [17].
Elling etal. showed that more than 50% of emergency medical technicians were
not able to ventilate a mannequin, and De Regge etal. showed that around 84% of
emergency room nurses were not able to adequately perform mask ventilation [18,
19]. The dexterity of face mask ventilation is acquired through proper training and
maintained subsequently by daily practice. Learning curves are more rapidly
acquired and less variable for mask ventilation than for tracheal intubation. Komatsu
etal. showed that novice interns reached a 20% failure rate or better after a median
of 25 procedures [20]. Davidovic etal. showed that trainee participants in a pediatric context demonstrated improved tidal volumes and inspiratory pressures when
practicing two-person compared to one-person MV [21]. Cocucci etal. showed that
training accurate respiratory rates during pediatric MV can be improved with the
use of a metronome [22].
Simple maneuvers might be used to achieve a tight seal in patients with distorted
anatomy. Examples include inverting the face mask over a cast nose or keeping the
dentures in edentulous patients [23]. In obese patients with relatively large facial
structures, it is recommended to use both hands; as with only one hand, it is practically difcult to appropriately perform airway maneuvers including mouth opening.
After failed intubation during rapid-sequence intubation, inadequately applied cricoid pressure may induce airway obstruction and result in DAM [24].
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M. S. Rizk et al.
Equipment Conditions
During an emergency airway situation, time is of major importance whether the
patient is difcult to intubate or is difcult to ventilate. The location and storage of
equipment in operating rooms are important for easy and quick accessibility. Storing
all the necessary equipment in a designated “difcult airway cart” (DAC) will save
time and effort when an emergency occurs. It is recommended that the DAC should
include a jet ventilator, ber-optic bronchoscope, intubating stylet, video laryngoscope, intubating laryngeal mask airway, Combitube, various laryngoscope blades
(i.e., Miller and Macintosh), an articulating laryngoscope, and different sizes of
oropharyngeal and nasopharyngeal airways (OPAs and NPAs).
The DAC drives efciency in all the units where intubations are frequently performed, i.e., emergency room (ER), intensive care unit (ICU), and operating room
(OR). It is also very effective in areas outside the general operating room where
advanced airway equipment may not be readily available for surgical use.
The availability of a DAC with many new alternative airway devices, adoption of
the ASA difcult airway algorithm, and better monitoring techniques have resulted
in safer airway management practices and reduced the incidence of these serious
complications [25, 26].
Patient Conditions
Head Position
Suboptimal head and neck positioning may lead to DAM [27]. The snifng position
increases the pharyngeal space, which may render MV more efcient [28, 29]. Neck
exion, head extension, chin lift, and jaw thrust (the triple maneuver) are important
simple techniques to increase pharyngeal patency.
Obesity
Obesity is recognized as one of the risk factors for difcult and challenging MV
[30]. Lung volume, pharyngeal collapse, and increased chest wall rigidity impact
difcult MV, particularly in patients with sleep-disordered breathing (SDB) and
obesity. Obesity negatively impacts SDB by increasing pharyngeal airway collapsibility through structural mechanisms such as excessive soft tissue for the craniofacial size and reduced lung volume. Preoperative screening for obesity, lingual
tonsils, and patients with a history of SDB is crucial in an effort to prevent difcult
MV [31–33].
In their study comparing mask ventilation in normal patients and patients with
multiple risk factors for SDB, Sato etal. found that expiratory ow limitation (EFL)
and obesity independently account for reduction of mask ventilation efciency. The
study indicated that the use of two hands can effectively, though not perfectly, compensate for the structural abnormalities resulting in acceptable MV even in severe
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SDB patients. The tidal volume during one-handed MV increased by more than
70% during the rst minute [31]. This has been attributed to the deepening of anesthesia and onset of neuromuscular blockade.
Safar etal. recommended the use of oral or nasal airways to prevent the EFL at
the soft palate and further improve the MV [16]. Also, the right positioning may
improve conditions for effective mask ventilation, such as adopting antiTrendelenburg or Fowler positions to reduce abdominal pressure on the diaphragm [34].
299
Trauma
Trauma patients should be managed as having difcult airway. Special strategies are
required for airway management in trauma patients. When dealing with a trauma
patient, one has to take into account several predisposing factors for difcult airway
such as cervical spine injury, full stomach, hemodynamic instability, and lack of
cooperation. Choices for airway management may be limited due to lack of patient
cooperation and time pressure. The option of waking a trauma patient after failure
to secure a patent airway might not be possible. The gold standard is an awake beroptic intubation, which might turn out to be impractical or impossible in massive
face trauma bleeding. Thus, in certain cases, it might be safer to proceed with a
surgical front-of-neck access.
Other Patient Considerations
Opioid Induced
High doses of opioids may cause DMV by decreasing ventilatory compliance. This
phenomenon was rst described by Hamilton and Cullen in 1953. The chest and
abdominal wall rigidity induced by opioids was always thought to be the main reason for DMV [35]. In 1983, Scamman showed that patients with tracheostomies
experienced only a slight decrease in pulmonary compliance after high doses of
fentanyl induction [35]. Later, Abrams etal. published similar ndings in intubated
preinduction patients who received high-dose opioid [36]. Bennet etal. went further
in demonstrating closure of the glottis and supraglottic structures as the proximate
cause of difcult ventilation after induction with 3microg/kg sufentanil by using a
ber-optic bronchoscope to examine the vocal cords before and after narcotics.
Vocal cord closure occurred in 28 of 30 patients after sufentanil administration and
improved only after muscle relaxant administration. They concluded that vocal cord
closure is the main mechanism of opioid-induced DMV [37]. Animal studies show
that the underlying mechanism of vocal cord spasm and muscle rigidity is central
stimulation of microreceptors through efferent motor trafc, particularly to the
laryngeal muscles [38].
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Succinylcholine-Induced Masseter Spasm
The masseter muscle responds to the initial depolarization by a contracture. Usually,
this response is transient, and masseter spasm resolves when fasciculation stops.
Moreover, succinylcholine is known to cause signicant masseter spasm in children
when used in conjunction with volatile anesthetics such as halothane. Sometimes in
adults, it can result in clinically signicant jaw rigidity (jaw of steel), impeding
ventilation and intubation attempts [39]. Masseter spasm can be a benign phenomenon, but it may also be an early sign of malignant hyperthermia [40].
Non-depolarizing Muscle Relaxation (NDMR)
andLight Anesthesia
The effect of administration of NDMR on the ease of mask ventilation is controversial. Immediately after anesthesia induction, there may be some difculty with
MV. However, with the onset of muscle relaxation, this phenomenon gradually
eases, and adequate MV is eventually established. Full neuromuscular blockade
might facilitate mask ventilation by increasing chest wall compliance or by reducing upper airway tone; alternatively, it could make mask ventilation more difcult
by inducing upper airway collapse [41, 42]. Therefore, it was concluded that muscle
tone was the factor behind the initial resistance to MV.
In accordance with Ikeda etal., our data showed that MV was not signicantly
affected with the use of NDMR [43]. We observed only a minimal and nonsignicant
increase in the percentage of patients with Cormack and Lehane (C&L) grade I who
were easy to ventilate before (93% of patients) and after (98% of patients) administration of NDMR.Furthermore, patients with C&L grades II and III exhibited a statistically nonsignicant trend toward a change in the quality of MV before (68% easy,
32% difcult) and after (60% easy, 40% difcult) administration of NDMR.The nonsignicant increase in the percentage of difcult MV in patients with C&L grades II
and III before (32%) and after (40%) NDMR could be attributed to the relaxation of
the oropharyngeal muscles and subsequent obstruction of the submandibular tissues,
in a group of patients already predisposed (i.e., C&L II and III) to difcult MV [44].
It is worth mentioning that impossible MV was not encountered in our patient population before and after administration of NDMR, similar to previous studies [42, 45, 46].
On the other hand, light anesthesia may induce coughing, increased chest wall
muscle tone, and paradoxical vocal cord movement and may be complicated by
tracheobronchial spasm. This phenomenon may cause DMV by reducing compliance and, consequently, decreasing chest wall expansion [47]. This critical situation
can be resolved by deepening of the anesthesia or by using muscle relaxants.
Upper Airway Obstruction
The most common causes of upper airway obstruction include pharyngeal wall collapse in morbidly obese and sleep apnea patients; this is mostly attributed to either
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a proportionally large tongue in relation to the pharyngeal space, tonsillar hyperplasia, or redundant tissues [48]. Upper airway obstruction can also occur after induction of general anesthesia with posterior displacements of the soft palate, base of
tongue, and epiglottis. Attempts at inspiration during anesthesia were found to
cause major secondary collapse of the pharynx with multiple sites of obstruction,
similar to that found in obstructive sleep apnea [49]. In patients with a slight
increased BMI with no apparent signs of airway abnormalities, a difcult airway
may not be anticipated, leading to a more difcult airway management, whereas
there is a low threshold for awake intubation in morbidly obese patients [50].
Other causes such as pharyngeal and neck tumors may obstruct the upper airway
[51]. Facial and maxillary tumors may cause face deformity, leading to impingement on the upper airway and DAM [52]. Other tumors affecting the thyroid or the
larynx can all produce different levels of upper airway obstruction leading to DAM
[53]. Trauma to the upper airway, including iatrogenic trauma induced by repeated
attempts at tracheal intubation, can lead to bleeding, swelling, and edema of the
pharyngeal and laryngeal structures [54]. Carotid pseudo-aneurysms may bulge into
the pharynx, causing partial obstruction [55].
301
Distal Airway Obstruction
It is recommended that patients with distal airway obstruction, mostly tracheomalacia and mediastinal masses, should be intubated while awake. In these cases, induction with muscle relaxant will cause relaxation of the parasternal muscles leading to
extrinsic airway compression. Subsequently, this will lead to decreased expiratory
ow and elimination of diaphragmatic movement leading to impossible
ventilation.
DMV might also be caused by severe bronchospasm, stiff lungs, bronchopleural
stula, pneumothorax, foreign body aspiration, bronchial tumors, severe kyphoscoliosis, and chest wall deformity, all of which impede lung expansion and reduce
compliance [56]. In these situations, the practice of testing the possibility of MV
prior to the administration of neuromuscular blockers is no longer supported [40].
When facing a DAM, it is imperative to go through this list of differential diagnoses to try to correct the reversible causes, or consider alternative interventions if
initial measures fail.
Evaluation ofDifficult Airway Management
Expertise in airway management is a critical clinical skill for anesthesiologists.
Major morbidities due to complicated airway management can be the most lifethreatening. MV is a core skill in airway management, as it proves to be a lifesaving
technique when all others fail. The Difcult Airway Society in 2015 shared guidelines for the management of unanticipated difcult intubation (DI) in adults. It
states MV as the third step after the failure of tracheal intubation and supraglottic
airway insertion [57].
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Even though MV can be a critical solution in difcult airway management, it can
also be difcult, challenging, or a source of complication. Aspiration is a common
complication of MV, which can be prevented. The patient should observe fasting
guidelines whenever possible. Draining the gastric content before proceeding to
airway management is another option. Application of cricoid pressure during MV
might help to reduce gastric distension, keeping in mind that cricoid pressure might
sometimes impede the ease of MV.Most of the time, a DMV can be improved by
some maneuvers such as administering neuromuscular blockade, head-up positioning, jaw thrust, two-handed mask ventilation, and use of oropharyngeal and nasopharyngeal airways [40]. Successful MV requires good technique and regular
practice. Poor MV performance can have adverse physiological complications, particularly during emergency airway management when the operator starts to hyperventilate forcefully. This hyperventilation leads to decreased PaCO2,
vasoconstriction, and gastric insufation. Ventilating with small tidal volumes
(6–7mL/kg) and short ination duration of 1s are recommended; also avoid rapid
or forceful breaths [37].
Several algorithms for difcult airway management have been developed; the
most common component is the preoperative assessment to predict the difcult airway [4, 5]. Prediction is mainly based on factors focusing on difcult tracheal intubation. Yet the most critical situation is the case in which intubation is impossible
and mask ventilation is, or becomes, inadequate. The prediction of difcult mask
ventilation (DMV) is therefore of vital importance. Unfortunately, the factors to
predict DMV remain unknown and have not been dened in practice guidelines for
the management of difcult airway [4, 5]. Many authors have tried to predict
DMV. Asai etal. failed to anticipate DMV in 57% of the patients who were ultimately difcult to ventilate before anesthesia induction [58].
M. S. Rizk et al.
Expected Difficult Tracheal Intubation (DTI)
Before the procedure, patient airway evaluation is crucial. Patient’s history, oral
and maxillofacial anatomy, pharyngeal and laryngeal structures, and cervical
spine mobility must be assessed for signs that predispose to airway difculty.
Both the Mallampati score and the thyromental distance require special attention.
A view of the oral cavity can show the size of the tongue, adequacy of mouth
opening, and condition of the teeth and uvula. The less the uvula is visualized
behind the tongue and the closer the chin is to the chest wall with the head in midposition, the more difcult the intubation is expected to be. Moreover, obesity,
wide neck circumference, and a drastic overbite promote difculty in airway
management.
If a difcult airway is anticipated, awake ber-optic intubation is recommended
to be performed in cooperative patients. Physicians who do not routinely perform
ber-optic intubations should not attempt a difcult airway, except in an emergency
setting. Failed intubation attempts may lead to trauma and increase in bleeding,
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