Upper Airway Obstruction

Etiology

Upper airway obstruction can be classified by the type of noisy breathing it can cause (ie, stertor or stridor). 

Stertor

A blockage can cause stertor at the level of the oral or nasal cavities or the level of the oropharynx or nasopharynx. Causes of a blockage at this level can be classified as congenital or acquired. Congenital causes of the nasal cavity or nasopharyngeal airway obstruction can cause symptoms soon after birth. Neonatal anatomy dictates that newborns are obligate nasal breathers for the first few months of life.[1] This ensures that they can breathe and feed simultaneously. Pyriform aperture stenosis and bilateral choanal atresia are rare but important causes of upper airway obstruction at this level.[2][3] 

Bilateral choanal atresia will cause immediate upper airway obstruction and distress at birth, relieved by crying facilitating breathing via the oral cavity. Acquired causes of nasal or nasopharyngeal obstruction include nasal turbinate hypertrophy secondary to allergic rhinitis, nasal polyposis, nasal foreign bodies, septal deviation, or adenoidal hypertrophy. Congenital causes of upper airway obstruction at the level of the oral cavity include retrognathia (either isolated or associated with Pierre Robin Sequence), glossoptosis, macroglossia, and lymphovascular malformation. Acquired causes at this level include angioedema, Ludwig angina (floor-of-mouth abscess secondary to dental infection), oral cavity or oropharyngeal cancer (squamous cell carcinoma most common, also considered lymphoma of tonsils), tonsillar hypertrophy, and parapharyngeal/retropharyngeal/peri-tonsillar abscess. Potential traumatic causes include penetrating neck injury, burns, or caustic injury, all of which can cause edema.

A very common cause of stertor in children is adenotonsillar hypertrophy. This can lead to obstructive sleep apnea (OSA).[4] Symptoms of OSA in children include snoring/stertor, frequent night awakenings, hyperactivity, poor concentration in school, and enuresis.[5] It is important to perform sleep studies in children with a history suggestive of obstructive sleep apnea and concurrent craniofacial abnormalities or complex medical histories to determine the severity of their OSA. In a sleep study, apnea and hypopnea events are recorded. These are reported as the Apnea-Hypopnea Index (AHI). The AHI correlates to the sum of the number of apneas and hypopneas per hour during sleep. Apnea is the cessation of airflow for more than or equal to ten seconds, and hypopnea is classified as a reduction in respiratory effort with greater than 4% oxygen desaturation.[6] A sleep study result showing an apnea-hypopnea index above 1 is abnormal in a child.[7]

Adults also experience OSA; however, OSA in adults has a different grading system for severity. Less than 5 events in an hour are normal, 5 to 15 demonstrate mild sleep apnea, 15 to 30 events correlate with moderate OSA, and anything above 30 is severe.[6]

Stridor

Stridor is a high-pitched sound associated with obstruction at the level of the larynx. Congenital causes include laryngomalacia, unilateral or bilateral vocal cord palsy, laryngeal web, subglottic stenosis, subglottic hemangioma, or tracheomalacia. Acquired causes in childhood include recurrent respiratory papillomatosis (RRP), vocal cord palsy, subglottic stenosis secondary to intubation, epiglottitis, tracheobronchitis/croup, and inhaled foreign body. Notably, subglottic stenosis or subglottic hemangioma can present like croup, as they both can cause a ‘barking cough.’ It is common for patients with these causes of stridor to be treated on multiple occasions in the Emergency Department before being referred to an otorhinolaryngologist or pulmonologist for further evaluation. Such evaluation includes direct microlaryngoscopy and bronchoscopy.

Colloquially known as "choking," foreign body aspiration is an emergency more frequently encountered in children than adults. Commonly aspirated materials in children include peanuts, buttons, and beads. One study showed that most inhaled foreign bodies in their cohort were organic material.[8] Objects like button batteries are especially dangerous, causing airway obstruction and caustic injury.[9] 

Laryngomalacia is a common but usually not life-threatening form of upper airway obstruction that affects mostly neonates and can become evident within the first year of life.[10] This is due to the relative immaturity and laxity of the laryngeal framework, which improves over time as the child grows. Laryngomalacia causes high-pitched inspiratory stridor and can be associated with feeding difficulties and failure to thrive.

Stridor in adults is usually worrying, as it can be a sign of laryngeal cancer. Adults with sudden onset stridor should be evaluated urgently, as it may signify a rapidly progressing airway emergency. Other causes of stridor in an adult include infectious causes such as epiglottitis or supraglottis, which bacteria, fungi, or mycobacteria may cause. Unusual causes of stridor in an adult include immunologic and auto-immune diseases such as Behcet’s disease, granulomatous polyangiitis, sarcoidosis, and amyloidosis. Acquired subglottic stenosis following prolonged intubation or trauma is also worth considering, especially in the case of biphasic stridor.

Bilateral vocal cord palsy is an uncommon but recognized cause of stridor. Airway burns are important causes of upper airway edema and inflammation, which may cause upper airway obstruction. Any patient following exposure to the fumes from a fire should be assessed, and anyone with singed nasal hairs and edema of the oral cavity should have a flexible nasendoscopy where possible and may need emergency intubation.[10] 

External compression of the trachea can occur as a congenital or acquired process. Some neonates are born with a vascular ring or aortic anomalies that cause tracheal compression. In adults, a slow-growing thyroid goiter can cause tracheal compression, as can other cancers of the head and neck that might impinge on the larynx or trachea.

Epidemiology

The epidemiology of upper airway obstruction varies as much as the etiological causes of this disorder. The following are a few of the most common causes of upper airway obstruction and their respective statistics.

Visits to emergency departments for choking incidents in children were studied by the Centers for Disease Control and Prevention (CDC) in 2000.[11] They reported that 160 children aged 14 years or less died of choking incidents. The number of visits for nonfatal choking incidents was around 17,537 that year. 

It is widely recognized that surgery for adenotonsillar hypertrophy is a common procedure. Quoted rates for these procedures vary from country to country and have been documented as anywhere between 19 per 10,000 children and 118 per 10,000 children.[12] In adults, obstructive sleep apnea has been reported as affecting 26% of the adult population of the United States.[13]

Head and neck cancers account for more than 650,000 cases and 330,000 deaths each year worldwide.[14] It also accounts for 3% of all malignancies recorded in the United States.[14] Men are more often affected than women, at a rate of 2 to 1 versus 4 to 1. 

Pathophysiology

When considering the pathophysiology of upper airway obstruction, it is imperative to understand the variations between adult and pediatric upper airway anatomy. Children have larger heads and a larger occiput, causing hyperflexion of the airway when lying flat and supine.[15] 

Children also have a larger tongue and smaller mandibles compared with adults. Their epiglottis is floppy and can obscure the view of the larynx on laryngoscopy at intubation. A pediatric larynx sits higher than in adults and is shaped like a funnel. The cricoid is at the C4 level at birth, dropping eventually to the C6 level at around age ten. Therefore, a cricothyroidotomy is not a viable procedure in a child younger than 10. Also, pediatric supraglottic cartilages are softer and more distensible than that of adults, leading at times to dynamic collapse, which is seen in laryngomalacia. It is also crucial to remember that babies must breathe nasally from birth for the first few months of life. Regarding the lower airway physiology, children consume more oxygen at rest than adults, as their resting metabolic demand is 2 to 3 times that of adults. They also have a lower functional residual capacity, which translates to a more precipitous onset of hypoxemia and hypercarbia during apnea.[16] 

Due to Poseuille’s Law, a small decrease in a child’s airway diameter can have a devastating effect. This can be caused by edema, stenosis, foreign body, or mucus. Babies from 36 weeks onwards have mature alveoli; however, these continue to develop with septation and microvascular maturation from birth until around 8 years of age.[17] Therefore, the surface area for gas exchange is less in pediatric patients.

The most narrow region of the adult airway is at the glottis level. Given that the most common cause of upper airway obstruction in adults is OSA, it is important to understand the physiologic processes involved in this presentation. These patients are often obese. They usually have an element of pharyngeal collapse, which can also be associated with retrognathia and underlying conditions such as hypertension and diabetes mellitus.[18]

History and Physical

A history must be elicited from a parent or primary caregiver in children. For example, OSA questions will be addressed to the adult accompanying the child and focus on inquiries involving a history of snoring with apneic episodes and either tiredness or hyperactivity the following day. Children with OSA due to adenotonsillar hypertrophy are described as "mouth-breathers" by parents. As previously mentioned, children can have various symptoms suggestive of OSA, such as hyperactivity and enuresis.

For adults with OSA, history can be slightly different. These patients complain of frequently waking at night and feeling unrefreshed the next day despite having spent the full night in bed. They often have a high body mass index and complain of hypersomnolence. Their cohabitants will often complain that they snore.

It is crucial to identify a patient with acute upper airway obstruction. Respiratory distress can quickly lead to respiratory failure without appropriate management. An urgent and comprehensive assessment of ABCs (airway, breathing, and circulation) must be performed while ensuring the patient is in a safe environment. Approaches differ depending on the patient's presentation.

Every effort should be made to complete an efficient ENT examination in patients at risk of upper airway obstruction, where safe and possible. Often, history and examination can take place simultaneously.

General Inspection

As with all patients, a general examination of body habitus, facial features (paying close attention to any syndromic features), and respiratory effort should take place as part of the comprehensive exam. Mental status should be noted. Any signs of tobacco use or signs of drug or alcohol intoxication or dependence should be assessed.

Children 

Children in respiratory distress may show increased breathing effort via accessory muscles. They also can present with nasal flaring, tracheal tug, intercostal and subcostal recession, and grunting.[19] If respiratory failure is reached, there is shallow breathing, bradycardia, and altered mental status. It is worth noting that altered mental status in an infant often presents as listlessness. Stranger anxiety is a normal developmental sign in babies aged 9 to 18 months, and the absence of this behavior is a worrying sign in a sick child. It is also very worrying if a small child does not resist some elements of examination and treatment, such as the placement of a needle or intravenous cannula. A particular case of critical upper airway obstruction in children can occur due to epiglottitis. In suspected epiglottitis of a child, they will classically present with a short history of sore throat, a muffled voice, and drooling. In advanced cases, the patient may be in the tripod position, a body placement that stents the upper airway open. If epiglottitis is the likely diagnosis, there should be no attempt to examine the oropharynx, as it may upset the child and cause devastating laryngospasm.[20]

Adults

Tachypnea and a feeling of shortness of breath, including failure to complete sentences, can signal respiratory distress in adults. In recurrent respiratory papillomatosis, an adult may present with chronic dysphonia and shortness of breath, which may progress to stridor. They may present with acute respiratory distress; however, in this scenario, they will have acute on chronic symptoms. 

Anterior Rhinoscopy

It is important to assess for septal deviation, hypertrophy of the nasal turbinates, or nasal polyposis during anterior rhinoscopy. A quick test to prove choanal patency can be performed by asking the patient to exhale nasally onto a cold metal spatula (nasal misting test).

Oral Cavity

The oral cavity should also be thoroughly examined, paying close attention to any signs of micrognathia, edema of the lips, trismus, floor of mouth or tongue edema, tumor, or palatal fullness with uvular deviation, as in the case of a peri-tonsillar abscess.

Additional Examination

A cardiorespiratory examination should take place when appropriate. Basic vital signs (ie, pulse, respiratory rate, blood pressure, and O2 saturation) should occur initially as part of the ABCs of assessment. Any noisy breathing and quality of the breathing, including dysphonia, should be noted. 

Evaluation

Following a basic history and exam, some investigations are necessary to diagnose the common and urgent causes of upper airway obstruction.

Flexible Laryngoscopy 

No comprehensive ENT examination is complete without flexible nasendoscopy/ laryngoscopy to dynamically assess the pharynx and larynx. This can help diagnose turbinate inflammation, septal deviation, adenoidal hypertrophy, Waldeyer’s ring hypertrophy, or laryngeal/hypopharyngeal pathology. It is particularly useful when assessing the dynamic function of the larynx. A dynamic assessment is essential when assessing vocal cord movement and relatively common conditions affecting the larynx, such as laryngomalacia in children. It can also diagnose a laryngeal tumor in adults.

Oxygen Saturation

Oxygen saturations are an essential first step in assessing a patient with airway obstruction, as they can be a marker of the severity of the obstruction.

Imaging 

Imaging studies help delineate the affected anatomical area and can also aid in the diagnosis of the cause of obstruction. Ultrasound or MRI are the imaging modalities of choice in children, as they do not involve radiation.[21] However, a general anesthetic is usually needed for a young child to tolerate an MRI. Therefore CT is used in situations that are time-sensitive or in cases that may need surgical intervention, such as a retropharyngeal abscess or a possible inhaled foreign body. If a child with a possible inhaled foreign body is stable, inspiratory, and expiratory, chest radiographs can aid in diagnosis. For example, suppose a foreign body partially obstructs the left main bronchus. In that case, there may be hyperlucency of the left lung due to hyperinflation secondary to the ball-valve effect of the foreign body.

Sleep Study

A sleep study or polysomnography should be performed to assess OSA formally. The important results of a sleep study are the patient’s oxygen nadir and the (AHI). The AHI averages the number of apneic and hypopneic episodes per hour. An AHI of anything above 1 is abnormal in a child, and there is a severity grading system for increasing numbers of AHI in adults.

Treatment / Management

As mentioned, the initial step in airway obstruction management is ABC. An oxygen saturation monitor should be placed, and oxygen by mask should be initiated. In a stable patient in the acute setting, there may be time to perform imaging studies, initiate antibiotic treatment, etc. In the unstable patient in the acute setting, it is crucial to efficiently assess the patient while taking a quick history/collateral history. Outside the hospital setting, an ambulance should be called. If choking is suspected, the Heimlich maneuver should be performed. In the unconscious patient's case, a pulse check should be performed, and the patient should be managed as per Basic Life Support Protocols (BLS) while waiting for an ambulance. In the case of acute airway obstruction in a hospital setting, a code should be called, and the Airway Team and the Medical Team involved in managing cardiorespiratory arrest should be called immediately. The nearest healthcare professionals should initiate the BLS algorithm.

Pediatric Inhaled Foreign Body

In the case of suspected inhaled foreign body in children, if the child is in respiratory distress and is unstable, the patient should be moved to the Operating Room (OR) immediately, and the most senior Pediatric ear, nose, and throat and anesthesiology team members should be involved as soon as possible. A direct microlaryngoscopy and bronchoscopy should be performed to remove the foreign body. The child should be supine with a shoulder roll to aid in the neck extension. Inhaled Sevoflurane and oxygen can be used to induce and maintain general anesthesia. It is usually preferable to maintain spontaneous respiration.[22] Occasionally, teams will use total intravenous anesthesia (TIVA) to maintain anesthesia.[23] In this case, propofol with or without remifentanil is used for good airway reflex suppression and quick emergence from anesthesia. Once asleep, a tooth guard or moist gauze (if the patient has no teeth) is used, and a laryngoscope is inserted to view the larynx. Lidocaine is sprayed on the vocal cords (e.g., 4% lidocaine is 0.1 ml per kg). An appropriately sized bronchoscope with a zero-degree Hopkin’s rod endoscope is inserted to view the trachea. If a foreign body is found, optical grasping forceps can be retrieved.(B2)

Management of Acute Upper Airway Obstruction in Adults

Awake fibreoptic intubation

In adults, there will often be different presentations requiring intervention. In the case of upper airway obstruction at the level of the oral cavity or oropharynx, it is important to secure an airway if impending airway obstruction is anticipated. For example, in the case of Ludwig’s angina, i.e., a bacterial infection of the oral cavity, causing tongue and floor of mouth edema, it may be possible to perform awake fibreoptic intubation. In this scenario, the providing physician slides an endotracheal tube (ETT) onto a flexible endoscope.[24] The nose is decongested, and the scope is passed to the glottis level while the patient sits upright. Lidocaine is inserted through the side port of the scope and onto the cords to anesthetize them to avoid laryngospasm. When this has worked, the scope is passed through the level of the vocal cords, and the ETT is then pushed down past the cords using the Seldinger technique. The patient is then given a general anesthetic, and the dental abscess is drained. The patient will likely need to be sedated for 1 to 2 days to allow the edema to settle before pulling the ETT.

Cricothyroidotomy 

In such cases where intubation would be considered difficult or impossible, a cricothyroidotomy is a very quick procedure that can be performed in adults in cases of a true emergency. While the patient is supine, the operator holds the larynx in place, makes a vertical incision between the thyroid and cricoid cartilage, and inserts a blunt instrument, such as a hemostat, through the cricothyroid membrane. This takes some force. It is helpful to insert a bougie with a lumen and then railroad a small, ie, size 6, ETT over this to secure the airway.[25](B3)

Tracheostomy 

Tracheostomy is sometimes necessary in upper airway obstruction cases where intubation is anticipated to be very difficult or impossible. This can be performed under local anesthetic. If time allows, it should be performed in the OR with experienced staff and with anesthesiology involved. Before the procedure, it is helpful to administer at least 5 to 10 ml of nebulized 1% Lidocaine. In the OR, the patient should have oxygen via a face mask or nasal prongs and be comfortable in a supine position or sometimes semi-recumbent if in respiratory distress. Occasionally, the anesthesiologist may administer medication, for example, ketamine, to reduce anxiety without suppressing the respiratory drive.[26] A solution of 1% lidocaine can be injected directly into the larynx via the cricothyroid membrane, and position in the airway can be confirmed by drawing air back into the syringe before injecting. A tracheostomy is then performed under local anesthesia using the usual steps.[27]

Management of Chronic Upper Airway Obstruction in Adults

A common cause of upper airway obstruction in adults is OSA. Aside from lifestyle modifications such as weight loss, Continuous Positive Airway Pressure (CPAP) manages this condition. It has been found that nasal-positive airway Pressure masks are more easily tolerated than orofacial masks.[13] The use of a nasal mask can be affected by structural ENT changes such as septal deviation and inferior turbinate hypertrophy, sometimes leading to surgery to correct these obstructions. In patients with mild to moderate OSA who have difficulty adhering to CPAP therapy, alternative therapies such as oral devices can be considered. These devices either advance the mandible (i.e., mandibular repositioning splints) or position the tongue anteriorly (i.e., tongue retaining devices).[28] These appliances effectively project soft tissue anteriorly off the posterior pharyngeal wall and improve airway patency. Another such device is a hypoglossal nerve stimulator, which can sometimes be used as an adjunct in patients with moderate to severe OSA who have struggled with CPAP use.[29] (A1)

Surgery is reserved for patients who have failed CPAP therapy and who have a treatable cause of obstruction or as an adjunct to CPAP therapy. Occasionally, as in the case of children with adenotonsillar hypertrophy, surgery can be the primary treatment. Nasal surgeries, including septoplasty and inferior turbinate reduction, have improved CPAP tolerance in some studies compared with no surgical intervention for nasal obstruction.[30] Uvulopalatoplasty is the most commonly performed procedure for OSA. This involves tonsillectomy if tonsils are present, shortening and tightening the soft palate, and sometimes reducing or resectioning the uvula. However, it successfully treats OSA in fewer than 50% of patients and is more likely to be successful in patients with mild OSA.[31](A1)

OSA in children is most commonly caused by adenotonsillar hypertrophy, for which surgery is performed to reduce the bulk of tonsillar and adenoidal tissue. It has been documented that a history of sleep-disordered breathing in the setting of enlarged tonsils and adenoids has resulted in adenotonsillar reduction surgery on almost the same frequency as for recurrent infections.[32](B3)

Differential Diagnosis

Congenital

Congenital causes of upper airway obstruction include craniofacial syndromes that cause midfacial hypoplasia, such as Apert and Crouzon syndromes.[33] Pierre Robin Sequence and other conditions causing micrognathia or retrognathia can cause upper airway obstruction.[34] Rare causes of congenital upper airway obstruction include bilateral choanal atresia or lymphovascular malformation of the tongue or neck.[35] Congenital subglottic stenosis is rare but can occur, especially in babies with Trisomy 21.[36] Congenital laryngeal web is a rare but important cause of upper airway obstruction in neonates.

Acquired

Pediatric acute

Acquired acute pediatric causes of upper airway obstruction commonly include infectious causes such as neck abscesses or croup. An inhaled foreign body is an uncommon but important cause of acute upper airway obstruction. Less common but worth mentioning are burns or caustic injuries to the upper airway.

Pediatric chronic

Adenotonsillar hypertrophy is the most common cause of chronic upper airway obstruction in children. Regarding laryngeal pathology, bilateral vocal cord palsy, subglottic hemangioma or stenosis, or recurrent respiratory papillomatosis should be considered. Acquired subglottic stenosis is possible if the child has had previous intubation or, most commonly, following prolonged or repeated intubations. 

Adult acute

In the acute setting of upper airway obstruction in adults, there are many infectious causes. Ludwig’s angina (ie, the floor-of-mouth bacterial infection secondary to dental infection) can cause trismus and severe tongue edema, an airway emergency. Peri-tonsillar abscesses and parapharyngeal abscesses are important differentials for trismus and sore throat. Supraglottitits can also occur in adults. Recurrent respiratory papillomatosis can cause acute or chronic upper airway in adults. Laryngeal cancer can present acutely with stridor and respiratory distress. Advanced untreated cancer of the oral cavity, oropharynx, or hypopharynx also poses a risk of upper airway obstruction.

Adult chronic

OSA is the most common cause of chronic upper airway obstruction in adults. Less common but potential causes of laryngeal pathology and subsequent airway compromise are tuberculosis, sarcoidosis, granulomatosis with polyangiitis, and Behcet disease.[37][38] Acquired causes of nasal or nasopharyngeal obstruction include nasal turbinate hypertrophy secondary to allergic rhinitis, nasal polyposis, nasal foreign bodies, septal deviation, or adenoidal hypertrophy.

Prognosis

In the acute setting, untreated upper airway obstruction causing respiratory distress can lead to respiratory failure and, ultimately, cardiorespiratory arrest. Obstructive sleep apnea is the most common chronic cause of upper airway obstruction. In children, the possible consequences of untreated OSA include failure to thrive, behavioral problems such as hyperactivity, poor performance in school, and cardiovascular disease. In adults, untreated OSA can cause impaired daytime function, including somnolence, metabolic dysfunction, and an increased risk of cardiovascular disease.[39][40][41]

Complications

If acute upper airway obstruction goes untreated, it can result in respiratory distress, which causes bradycardia and fatigue in the patient, ultimately leading to loss of consciousness and cardiorespiratory arrest.[42] If upper airway obstruction is due to foreign body aspiration, it can be acutely fatal. Smaller foreign bodies can enter the lungs, causing atelectasis, pneumonia, or pneumothorax.

It is important to recognize the potential complications of the most common cause of upper airway obstruction: OSA. Untreated OSA in children can cause cor pulmonale.[43] Untreated OSA in adults can result in heart disease, metabolic syndrome, impaired daytime function, somnolence, metabolic dysfunction, and an increased risk of cardiovascular disease or even car accidents.[44][45] 

The treatment goals are to reduce side effects from OSA, improve sleep quality, and reduce the apnea-hypopnea index (AHI). This often takes a multi-disciplinary approach, frequently led by Pulmonology. Once diagnosed, first-line treatment involves weight loss and positive airway pressure use at night.[46] Compared to no treatment, positive airway pressure, such as CPAP, has significantly improved disease severity, daytime somnolence, blood pressure, and motor vehicle accidents.[13]