Securing the airway in a dyspneic patient is a challenging task because of the myriad causes and presentations. Initial assessment may demonstrate factors indicative of upper airway abnormalities; however, they may not be specific nor sensitive enough to accurately predict difficult intubation. A well-equipped airway cart must be immediately available. A standardized escalating approach to secure the airway in a difficult situation begins with a rapid sequence of attempts at standard intubation, followed by attempted tube introduction over a bougie or using a flexible endoscope or laryngeal mask, and finally surgical interventions including cricothyrotomy or tracheotomy.
Encountering a patient with a tenuous upper airway is a daunting situation for most physicians. The fate of the patient depends on prepared professionals trained in the evaluation and management of the airway. While some causes of airway obstruction are evident, many difficult airway situations manifest at induction of anesthesia. Unanticipated difficulty encountered during routine attempted intubation may quickly deteriorate into a life-threatening emergency if ill prepared. The degree of difficulty is often influenced by the patient’s anatomy and health status, the clinical setting, and the ability of the practitioner . Otolaryngologists and anesthesiologists should jointly plan the management of the difficult airway to ensure successful control.
No universally accepted definition of the difficult airway exists, but in broad terms, difficult airway control may be defined as problematic ventilation using a face mask, incomplete laryngoscopic visualization, or as a difficult intubation with standard airway equipment. Difficult ventilation is the inability to deliver the necessary tidal volume via the face mask even when using an oral or nasal airway and necessitating another device such as the laryngeal mask airway. Difficult laryngoscopy is impaired visualization of the true vocal cords despite elaborate external laryngeal repositioning, more specifically a Cormack and Lehane grade 3 or 4 ( Box 1 ) . Difficult intubation has been defined as requiring external laryngeal manipulation, difficult laryngoscopy requiring greater than three attempts at intubation, intubation requiring nonstandard equipment or approaches, or the inability to intubate using all available methods.
Visualization of the glottis during direct laryngoscopy with Macintosh blade
- 1.
Full view of the glottis
- 2.
Partial vocal fold or posterior commissure view
- 3.
Epiglottic tip visualized
- 4.
No exposure of glottic structures
Establishment of standards of care, a management algorithm, and a working knowledge of common equipment are crucial. Organization and coordination among otolaryngologists, anesthesiologists, emergency room physicians, and hospital staff are critical to foster a working environment that has a positive impact on patient outcome. Recognizing deficits and developing a systematic approach to the airway is an important step for improving patient safety and providing good outcomes.
Complications related to management of the difficult airway have significant impact on our patients. The inability to obtain and maintain an airway after induction with general anesthesia is a cause of nearly one third of anesthesia complications, with a large portion of these resulting in significant morbidity or mortality . The incidence of difficult intubation in the operating room ranges between 1.15% and 3.80% , with failed attempts in 0.05% to 0.35% of cases . In the emergency department, difficult intubation occurs in 3.0% to 5.3% of cases with failure rates ranging from 0.5% to 1.1% . Hypoxia from the difficult airway is commonly due to :
- 1.
Excessive number of attempts performed by different operators unsuccessfully
- 2.
Subsequent attempts with the same devices
- 3.
Inadequate oxygenation between attempts
- 4.
Aspiration of gastric contents during face mask ventilation
- 5.
Traumatic edema of the laryngeal auditus
Evaluation
Patient evaluation may occur in a controlled setting in the clinic or preoperative holding area or while the patient is decompensating in the emergency room, operating room, or out in the field. Both the environment and patient stability dictate the scope of evaluation and management. The ability to quickly assess a situation, plan the approach, and intervene by successfully securing an airway is vital. A breadth of understanding of the airway anatomy in relation to patient age and underlying etiology are key to prepare for the subsequent intervention.
Elective
If the situation is not urgent, a detailed history is obtained. The progression or regression and severity of symptoms should be noted. The history must also address difficulty with previous general anesthesia, sleep apnea or snoring, head and neck abnormalities, and other coexisting disease that might impair the airway or prevent standard intubation.
Adults
Adults with an impaired airway may present with a myriad of symptoms secondary to the underlying etiology. Signs and symptoms include dyspnea at rest or on exertion, stridor, neck swelling, voice changes, hemoptysis, dysphagia, odynophagia, and cough. Causes of airway impingement vary greatly and include such categories as infection, malignancy, and trauma ( Table 1 ).
| (K)Congenital | Infectious | Toxins and trauma | Tumor | Endocrine | Neurologic | Systemic | |
|---|---|---|---|---|---|---|---|
| Above the larynx | Congenital syndromes (Pierre Robin, Treacher Collins, mucopolysaccharidoses, Down’s), tonsil and adenoid hypertrophy, micrognathia, nasal turbinate hypertrophy, lingual thyroid, choanal atresia, macroglossia, nasoseptal deformity | Submandibular, peritonsillar, retropharyngeal, parapharyngeal abscesses, mononucleosis, diphtheria, Ludwig’s angina | Maxillofacial trauma, retropharyngeal hematoma | Lymphangioma (cystic hygroma) juvenile nasopharyngeal angiofibroma, tongue neoplasia, neurogenic nasal tumor, teratoma | Myxedema | Central sleep apnea | Burn or inhallational injury, Wegener’s, obesity, allergic rhinitis |
| Supraglottic | Laryngomalacia | Epiglottitis, supraglottitis | Stenosis, intubation injury | Neoplasia | Angioedema, sarcoidosis, burn or inhallational injury | ||
| Glottic | Laryngeal stenosis, glottic webbing, laryngeal cleft, laryngeal atresia, vocal cord paralysis/paresis | Laryngitis, diphtheria, tuberculosis | Laryngeal fracture or soft tissue injury, stenosis, foreign body | Neoplasia, respiratory papillomatosis | Vocal cord paralysis/paresis | Hereditary angioedema, burn or inhallational injury | |
| Subglottic | Subglottic stenosis, tracheoesophageal fistulae, vascular sling or ring, aortic arch abnormalities | Laryngotracheal bronchitis | Subglottic stenosis | Neoplasia, fibroma, hemangioma, papilloma | Thyromegaly | Respiratory muscle paralysis | Wegener’s |
| Tracheobronchial | Tracheal stenosis, tracheomalacia, bronchogenic cyst, vascular ring, bronchial web | Tracheitis, bronchitis, tuberculosis | Chronic obstructive pulmonary disease | Neoplasia, fibroma | Goiter | Asthma, burn or inhallational injury |
In an adult, the examination should carefully note facial and neck masses and deformities, scars, quality of dentition, maxillary and mandibular position, pharyngeal structures, and neck mobility. Flexible fiber-optic endoscopy provides a “tour” of the interior of the nose, nasopharynx, pharynx, larynx, and upper trachea. This endoscopy is the most important factor in determining the status of the upper airway and the cause of the impairment.
Predictors of a significantly difficult or impossible intubation in adults include the following :
- 1.
Interincisor distance 3 cm or less
- 2.
Thyro-mental distance 6 cm or less
- 3.
Maxillary dentition interfering with jaw thrust
- 4.
Malampati classification 4 ( Box 2 )
Box 2
- 1.
Clearly visible tonsils, tonsillar pillars, and soft palate
- 2.
Only visible uvula, tonsillar pillars, upper tonsillar pole
- 3.
Partially visible soft palate
- 4.
Only visible hard palate
Modified Malampati
- 1.
- 5.
Neck in fixed flexion
- 6.
Extreme head and neck radiation changes, scarring, or large masses
Additionally, some authors suggest increased age, male sex, history of obstructive sleep apnea, high body mass index, and pretracheal soft tissue may portend a challenging issue . However, other authors did not find high body mass index, neck mobility, increased age, thyromental distance, male sex, or high Malampati score as reliable measures in predicting a difficult airway . Additional factors that may affect a practitioner’s ability to manage the airway include amount of facial hair, dentition, and a history of chronic obstructive pulmonary disease, asthma, or snoring .
Children
Parents of young children are questioned about noisy breathing during exercise, at rest or when feeding, previous surgeries or intubations, neck pain, fever, recent upper respiratory infections, birth trauma, and congenital anomalies. The history of an unexplained coughing episode is suggestive of a foreign body of the larynx, trachea, or bronchi.
The physical examination must note the respiratory rate, nasal flaring, and accessory muscle use. Stridor, cough, and voice changes are frequently seen. Generally, most cases of acute airway compromise in children are due to infections, foreign bodies, and trauma; however, congenital malformations, neoplasia, and iatrogenic injury are additional considerations.
Anatomic differences between the adult and pediatric populations include larynx location in the neck, increased airway collapsibility (which attributes to easy obstruction in younger patients), size of occipital bones, relative tongue size, decreased functional pulmonary reserve, and less developed accessory muscles of respiration. The pediatric airway is much smaller than the adult airway in all dimensions including diameter. As the area of the circle is equal to the square of the radius, a very small change in the radius will result in dramatic changes in the patency of the airway. These factors and others help explain why tolerance of apnea and hypoxia is low in infants and children and why situations may quickly sour in a difficult pediatric airway situation. Of note, as a child grows, laryngeal anatomy continually changes; therefore, successful intubation at one point in time does not guarantee future success.
Predictors of a significantly difficult or impossible intubation in pediatric patients include small mouth aperture, hyomental distance 1.5 cm or less in a newborn or infant and 3 cm or less in a child, head and neck impaired mobility (especially in certain syndromes, eg, Downs, juvenile rheumatoid arthritis, Goldenhar), micrognathia, retrognathia, mandibular dysplasia/hypoplasia, macroglossia, space occupying airway lesions, supra-laryngeal inflammatory pathology, nasal airway obstruction, pathologic obesity, and craniofacial abnormalities .
Imaging studies
Radiographic studies may be diagnostic. A chest radiograph may detect a foreign body or large airway obstruction. A CT or MRI of the neck and chest may identify structural causes for airway impairment.
Urgent
Emergent airway cases warrant a concurrent history and physical with careful analysis of acquired information when possible. In an emergent life-threatening situation, the history and physical examination should be undertaken simultaneously. An adult may tolerate slight airway impairment and while a child may initially accommodate to an inadequate airway, increased work required for respiration will recruit accessory muscles until a state of exhaustion is reached or until the airway becomes too narrow to support respiration. The impending respiratory compromise mandates immediate securing of the airway. Since stridor is a symptom and not a diagnosis, a systematic approach must be taken to quickly reach an accurate conclusion ( Box 3 ). Acute stridor may be brought about by an upper respiratory illness exacerbating an underlying anomaly affecting the airway. Additionally, esophageal foreign bodies may push anteriorly against the trachea and impinge upon the airway.
S: severity of subjective impression regarding the severity of the obstruction
P: progression of symptoms
E: eating or feeding difficulties, aspiration
C: cyanotic episodes
S: sleep, any obstruction affecting sleep
R: radiology, specific abnormalities detected
Flexible laryngoscopy may be of immediate assistance during airway evaluation. This should include visualization of bilateral nasal cavities, the nasopharynx, and laryngeal anatomy.
Equipment
Every operating room should be equipped with a dedicated airway management equipment cart. This should be in a location that is readily available and contain instruments for both adult and pediatric patients. Standard equipment should include rigid laryngoscope in multiple sizes with both straight and curved blades, cuffed endotracheal tubes ranging from 2.0 to 8 mm ID, CO2 detector, tracheal introducer, malleable stylet, Magill forceps in adult and pediatric sizes, laryngeal mask airway (LMA) devices in multiple sizes, face masks for adult and pediatric patients, and a cricothyrotomy set. Additional equipment that may be needed includes flexible fiber-optic scope and light source, nasal trumpet, oral airway, and high-frequency jet ventilator. These devices should be properly maintained and checked for functionality. A dedicated pediatric airway cart should also be readily available.
Across hospitals and emergency rooms, a wide variety of equipment and instrument availability is encountered. This may be because of a lack of clinical data supporting the benefit of one approach over another, operator preference, equipment cost and maintenance required, skill and training of staff, and potential related complications .
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