Intubation Injuries and Airway Management
Otolaryngologists are frequently asked to evaluate patients who are endotracheally intubated and remain difficult to extubate or have voice or airway complaints after being extubated. Translaryngeal intubation may result in damage to the glottis, the subglottic segment, or the trachea itself. It usually follows periods of prolonged intubation with a translaryngeal cuffed tube in an intensive care setup for ventilation support. It has been observed that intubation injuries are less frequent but more severe in infants and children than adults, probably because children are more likely to have congenital anatomical abnormalities combined with a small airway or are commonly subject to improper tube selection for intubation.
Any physician being asked to evaluate a patient having dyspnea and/or dysphonia after extubation should be aware of both the acute and long-term intubation complications and understand their diagnosis, management, and prevention.
The first endotracheal intubation was performed as early as ad 1000. In 1878, MacEwen first described orotracheal intubation using a brass tube for the administration of anesthesia. Annandale, in 1889, designed a tube fabricated of rubber. Later, Guedel and Waters added an inflatable cuff to such a rubber tube.1,2 In 1964, the first polyvinylchloride tube with an integrated inflatable cuff was marketed. High-volume, low-pressure cuffs were introduced in 1970. Polyvinylchloride has the advantage of being less traumatic because it softens slightly at body temperature compared with room temperature, whereas rubber becomes more rigid and has a greater possibility of inducing mucosal injury. Furthermore, rubber endotracheal tubes (ETT) do not have high-volume, low-pressure cuffs.
Mechanism of Intubation Injury
Intubation injuries can be broadly classified into immediate and late. Immediate or acute injuries are those that occur during the initial intubation. These can occur during a traumatic on-site intubation when airway visualization is difficult due to severe upper airway bleeding or due to inadequate instrumentation or an inexperienced staff. Injuries in this type of intubation include mucosal abrasion, vocal cord hematoma, laryngotracheal tears and dislocation of the cricoarytenoid joint space.
Once the patient has been intubated, the most important consideration is of the airway mucosal capillary perfusion.3 It is important to note that the glottic shape is triangular, being broad at the posterior commissure and narrow at the anterior commissure. The ETT exerts pressure in the posterior larynx at four main sites ( Fig. 16.1 ):
medial surface and the vocal processes of the arytenoid cartilages and cricoarytenoid joints
posterior glottis consisting of the interarytenoid region
subglottis, which is more vulnerable in infants and small children because the cricoid ring is relatively small compared with that of the adults
trachea at the site of the ETT cuff.
In a patient with prolonged intubation, an ETT with circular cross-section occupies the interarytenoid space of the triangular glottis. If such a patient is not adequately sedated, the vocal process of the arytenoid cartilages is traumatized during their adductive movements, causing mucosal abrasion. Prolonged intubation causes pressure necrosis and mucosal ischemia leading to congestion, edema and ulceration leading to perichondritis and potential chondral necrosis ( Fig. 16.2 ). The final stage of a laryngeal “bedsore” is reached when there is necrosis of the cricoarytenoid joint and the cricoid cartilage. All of these events, along with fibrocicatrization, lead to laryngeal stenosis.
Factors Contributing to Intubation Trauma
Difficult anatomy—as in obese, short-necked individuals, protruding anterior teeth, retrognathic mandible, and restricted mouth opening
Difficult intubation of congenitally malformed larynges (webbing, cartilagenous stenosis)
Bleeding in the upper airway, which makes the intubation difficult and risky
Severely inflamed larynges are more prone to injury, as in acute laryngotracheobronchitis where the inflammatory response already present within the larynx makes the mucosa more susceptible to pressure necrosis
Acute or chronic diseased status (altered consciousness, poor tissue perfusion, diabetes mellitus). Medical conditions associated with decreased tissue perfusion increase the likelihood of tissue necrosis and ulceration. These conditions include head trauma, congestive heart failure, liver failure, hypoxemia, and anemia. Gaynor and Greenberg4 noted a very high incidence of severe complications in patients with insulin-dependent diabetes mellitus. Immunosuppressed patients are more prone to bacterial infection of the airway mucosal ulcerations and should be closely monitored for the development of chronic chondronecrosis and its sequelae.
Gastroesophageal reflux and aspiration are common in critically ill patients. This repetitive bathing of the laryngeal structures with gastric acid causes a chemical irritation that adds to local injury from the ETT. It may be beneficial to use H2-blockers or proton-pump inhibitors to minimize reflux in critically ill and intubated patients.
The presence of a nasogastric tube increases the likelihood of reflux. Nasogastric tubes may also cause irritation and ulceration in the postcricoid region causing cricoid ulcers. Injury caused by nasogastric tubes may occur with or without endotracheal tubes, and the concurrent presence of both may worsen the insult.
Intubation by novice in-training resident doctor, repeated intubations
Duration of intubation is an important factor contributing toward intubation sequelae. Normally intubation side effects can be seen within about 5 to 7 days in an adult and 7 to 14 days in children, noting here that infants do not have a specific time limit of intubation and could undergo continued intubation for 2 to 3 months if required, without performing a tracheotomy; however, this certainly invites a high risk of long-term intubation problems.2 Patients who undergo surgeries of long duration are at increased risk of developing intubation injury sequelae.
Physical characteristics of the tubes, i.e., size and type, are also important in determining intubation injuries. Large-size, rigid or rubber tubes are more traumatic and hence siliconized smooth-walled less irritating tubes are preferred. During an elective endotracheal intubation, recommended ETT norms are a 6.5-size (outer diameter 8.8 mm maximum) for an adult female and 7.5-size tube (outer diameter 10.2 mm maximum) for an adult male.5 In infants and children less than 8 years old an uncuffed tube with a diameter that allows an air leak in the subglottic space with a ventilating pressure of 20 cmH O is preferred.6 High-volume, low-pressure cuff has2 an additional advantage of reducing pressure-induced mucosal ischemia.
The ETT cuff may still induce excessive trauma if it is inflated too high within the larynx. Even with an appropriately sized ETT, excessive motion of the tube may induce repeated mucosal trauma. This may occur as a result of inadequate patient sedation, transmitted movements from the ventilator or manipulations during suctioning.
The evaluation of a patient with suspected intubation injury begins with a thorough history, and the following points should be carefully noted:
The reason for intubation and any coexisting illnesses
The date of initial intubation, failed attempts at extubation, and total duration of intubation
The mode of intubation, i.e., fiberoptic/rigid bronchoscopy-assisted/blind. Needless to say that more initial airway damage can be expected of a blind awake intubation
The place where the patient was intubated—hospital intubations would be more secure than on-site intubations, where lack of optimal instrumentation, inadequate oropharyngolaryngeal suctioning and thereby inability to correctly visualize the glottis adds to to the injury list
Details of securing the tube should be explored, as a wrongly secured tube in the posterior interarytenoid area increases the chances of a posterior glottic stenosis
Level of consciousness and whether excessive movements due to inadequate sedation and ventilator movements are transmitted to the tube
Route (orotracheal versus nasotracheal) of intubation
Size of the tube and presence of a nasogastric tube.
Laryngeal Examination in Patients with Suspected Intubation Trauma
Extubated Symptomatic Patient
In an adult patient, awake dynamic airway examination is performed with a flexible fiberoptic nasolaryngoscope to see the vocal cord mobility. Similar examination in children is performed under spontaneous respiration anesthesia with sevoflurane. All areas of the airway are examined systematically beginning with the nasal cavity, posterior choana, rhinopharynx, oropharynx, larynx, trachea, and bronchi. It must be pointed out that anesthetic drugs can modify the interpretation of dynamic airway functions, and hence the role of an experienced pediatric anesthetist and an optimal plane of anesthesia are very important. In a tracheostomized child, the cannula should be removed and the tracheostomy blocked temporarily to allow normal inspirium and expirium, thereby allowing precise identification of the airway obstruction.
Following dynamic examination, a direct laryngoscopy with 0° and angled optics should be performed for a complete evaluation of the endolaryngeal intubation injuries involving the supraglottis, glottis, and subglottis. During suspension microlaryngoscopy, examination with rigid 0° and 30° scopes is indispensable to identify injury at the posterior glottic level. A false vocal cord retractor is used to better expose the posterior glottis, which may show a cicatricial bridge between the two arytenoid cartilages. Direct palpation of the arytenoid cartilages may reveal fixation of the cricoarytenoid joints. The trachea, bronchi, and esophagus are carefully examined. It is not infrequent to see multisite airway narrowing, which eventually could affect patient treatment.
Benjamin2 advocates direct laryngoscopy in adult patients who had more than 7 days of intubation or in children 1 to 2 weeks after extubation that present with voice or respiratory symptoms and in infants after failed attempts at extubation.
Examination of the larynx is often challenging in an intubated patient. In patients who cannot be moved out of intensive care units, a bedside laryngoscopy with a McIntosh laryngosope and rigid 0° plus angled sinonasal endoscope is performed. In patients who are at high risk of developing a stenosis, the evaluation is made in the endoscopy suite aided by an anesthetist. During direct laryngoscopy, the ETT is removed, allowing complete examination of the glottis, the posterior glottis, and the subglottic region. The rest of the endoscopy protocol is similar to that described earlier for an extubated symptomatic patient. After visualizing the glottic injury, epinephrine-soaked cotton pledgets are used to decongest the laryngeal edema.
The patient is reintubated with an ETT that is one size smaller and an antibiotic–cortisone ointment plug is inserted into the glottis to calm the inflammatory process. Additional systemic corticosteroids and antibiotics are given (or continued). In children, if feasible, noninvasive ventilation methods like continuous positive airway pressure and bilevel positive airway pressure should be used as an alternative to continued endotracheal intubation. An intubated patient is under antibiotic cover and 24 hours before extubation, intravenous corticosteroid is administered to reduce the laryngeal edema and inflammation and aid the extubation. Epinephrine and steroid aerosols can be continued after extubation if needed.
Patients brought to the endoscopy suite in an intubated state need to be evaluated during spontaneous respiration to rule out arytenoid fixation or other pre-existing extralaryngeal causes for airway obstruction, which could pose problems at extubation and after. This emphasizes the role of a previous detailed patient history.
Immediate/Acute Complications of Intubation
A myriad of nonspecific and unfortunate complications have been reported after attempted intubation of patients with difficult anatomy or performed by inexperienced clinicians. These include rare reports7 of inadvertent esophageal intubation leading to swallowing of the ETT, laryngoscope bulb aspiration, and gastric perforation. More frequent complications include difficult intubation that may result in dental trauma, laceration to the mucosa of the oropharynx, hypopharynx, larynx, trachea, or esophagus, with the pyriform sinus being at the highest risk.4 The endolarynx is especially vulnerable because of its delicate anatomy. Acute postintubation injuries are summarized in Fig. 16.3 and illustrated in Fig. 16.4 .
Dislocation of the Arytenoid Cartilage
Dislocation of the arytenoid cartilage is a rare acute complication of intubation. The most common symptom is hoarseness, followed by breathlessness, dysphagia and vocal fatigue. The diagnosis is usually made by detection of decreased vocal fold mobility and anterior tilting of the arytenoid at indirect or flexible laryngoscopy. The vocal-fold is lax with submucosal arytenoid hematoma and shortened compared with the opposite side. The most consistent finding is the two vocal folds showing an unequal level. Early repositioning of the arytenoid is best performed at the time of diagnosis because this improves the likelihood of normal voice restoration. Prolonged dislocation may lead to cricoarytenoid joint ankylosis with complete joint fixation. However, there is no clear time period as to when this occurs and reductions as late as 1 year from the initial injury have shown dramatic improvement in voice quality.1,8
The arytenoid reduction procedure is performed under general anesthetic and suspension microlaryngoscopy. The dislocated arytenoid is repositioned posterolaterally and reaccommodated into the articular facet of the cricoid cartilage using a blunt-angled microlaryngoscopic instrument. It should be inserted into the Morgagni ventricle and pulled back until the arytenoid sits in its proper position. Sataloff et al9 recommend local anesthesia and sedation because this allows assessment of the voice and vocal fold mobility intraoperatively. There are reports of patients with spontaneous reduction of the dislocation needing no further surgical intervention.9 Bilateral ankylosed cricoarytenoid articular spaces together with a posterior glottic stenosis (PGS) present as frozen larynx, which is disastrous for the patient and a very difficult condition to treat.
Treatment of Acute Intubation Lesions
In clinical practice, two situations may occur: (1) swelling of the lax glotto–subglottic mucosa without ischemic necrosis, and (2) ulcers with fibrin and granulation tissue resulting from ischemic necrosis of the glottic and subglottic mucosa.
Treatment of Soft Tissue Stenosis without Mucosal Necrosis
Airway obstruction manifests itself within a few minutes of or up to a few hours after extubation. Premature babies are more prone than older children to develop this condition.10 Treatment consists of:
Topical decongestion with epinephrine pledgets
Reintubation with an ETT that is one size smaller
Application of an endolaryngeal plug of gentamycin–corticosteroid
Ointment (Diprogenta [Merck, Sharpe and Dohme, worldwide])
Systemic antibiotics, corticosteroids and antireflux treatment.
With the above conservative treatment, most patients can be extubated within 2 to 4 days.
Anterior Cricoid Split
This operation was introduced by Cotton and Seid in 198011 to avoid a tracheotomy in premature babies. It is indicated in the presence of adequate pulmonary reserve provided that no other upper or lower airway obstruction exists. Strict criteria for proper indications have been established12 and include: at least two extubation failures secondary to a subglottic laryngeal pathology, weight greater than 1500 g, off ventilator support for at least 10 days, supplemental oxygen requirement below 30%, noncongestive heart failure for at least 1 month, no acute respiratory tract infection, and no hypotensive medications for at least 10 days before the procedure.13
Anterior cricoid split is based on the principle that an anterior vertical midline transection of the cricoid ring allows the cartilage to spring open. This helps leakage of submucosal edema fluid through the wound. The surgery is illustrated in Fig. 16.5 .