Continuing Education Activity

According to the National Safety Council’s statistics, foreign-body airway obstruction (FBAO) is the fourth leading cause of unintentional death, resulting in 5,051 documented deaths in 2015. In children under the age of 16, foreign-body airway obstruction is one of the leading causes of accidental deaths. Due to the prevalence and rapidity of unconsciousness and death associated with choking, all persons, including those outside of the health field, should have a basic understanding of how to care for a choking victim. Simple maneuvers taught to laypeople such as the Heimlich maneuver have been proven to save lives. This activity reviews presentation, causes, and evaluation of foreign-body airway obstruction (FBAO) and highlights risk factors and interventions that should be used by an interprofessional team to recognize and manage patients presenting with this condition.

Objectives:

• Review the risk factors causing a foreign body airway obstruction.
• Describe the range of presentation and physical exam findings of a patient with a foreign body airway obstruction and explain other possible diagnoses.
• Explain the evaluation and treatment of complete and partial foreign body airway obstruction.
• Summarize the importance of collaboration and communication amongst the interprofessional team to improve outcomes for patients suffering from foreign body airway obstruction.

Introduction

According to the National Safety Council’s statistics, foreign-body airway obstruction (FBAO) is the fourth leading cause of unintentional death, resulting in 5,051 documented deaths in 2015. In children under the age of 16, foreign-body airway obstruction is one of the leading causes of accidental deaths.[1] Due to the prevalence and rapidity of unconsciousness and death associated with choking, all persons, including those outside of the health field, should have a basic understanding of how to care for a choking victim. Simple maneuvers taught to lay-people, such as the Heimlich maneuver, have been proven to save lives.[2] Besides complete foreign body airway obstruction that is immediately life-threatening, partial airway obstructions can impede gas exchange and lead to dyspnea, pneumonia, and abscess formation.[3]

Etiology

Choking is the blockage or hindrance of respiration by a foreign body obstruction in the airway.[4] Humans possess mechanisms that protect them from choking, but in adults with neuromuscular impairment or children with narrow airways, these mechanisms may be insufficient to prevent airway obstruction. Glottal closure and the expiration reflex, a forced expiratory effort to eject laryngeal debris, are the primary mechanisms of preventing foreign bodies into the airway.[5] The expiration reflex differs from the cough reflex as the expiration reflex starts with expiration, and the cough reflex starts with an inspiration, implying different sensory or afferent inputs and central nervous processing.[6] The expiration reflex functions to prevent the aspiration of material into the lower airways while the cough reflex draws air into the lungs to promote a more efficient expulsion of mucus and airway debris.[6] Understanding the differences between the cough reflex and expiration reflex is also crucial from a pharmacological perspective as codeine, for example, does not affect the expiration reflex in doses that inhibit cough. At the same time, many other types of anesthesia will depress the expiration reflex more than the cough reflex.[7]

Several factors make children especially prone to choking. A child’s airway is much smaller than that of an adult. Since air resistance is inversely proportional to the cross-sectional radius to the fourth power (Poiseuille's law), a small object can have a drastic effect on a child’s ability to breathe. A child does not generate the same force when coughing as an adult, so their efforts may not be enough to dislodge a foreign body.[4] Additionally, children commonly put objects in their mouths, starting in infancy as they discover their environment.

Round foods are more likely to cause fatal choking in children, with hot dogs being the most common, followed by candy, nuts, and grapes.[8] Among non-food items, latex balloons are reportedly the leading cause of fatal choking events among children.[9] Latex balloons can conform to the airway forming a tight seal making it particularly dangerous to children.

For adults, autopsy results from 200 choking victims showed meat, fish, and sausage to be responsible for death in 71% of cases followed by bread and bread products (12%) and fruits and vegetables (7%).[10]

Epidemiology

The incidence of nonfatal choking episodes is difficult to measure because many of these events are transient and do not result in visits to a hospital.[4] Of the children who receive treatment for nonfatal choking, food is the most common precipitant, with 59.5% of cases followed by nonfood items, such as coins, marbles, balloons, and paper, with 31.4%. In 9.1% of cases, the cause was unknown.[11]

Among children, choking rates were highest among infants less than one year, and over 75% of choking incidents occurred in children under 3. No significant difference appeared in the choking rates between boys and girls.[11]

Among adults, conditions associated with a higher risk of choking include Alzheimer disease, parkinsonism, prior stroke, intellectual or developmental disability, poor dentition, intoxication, dysphagia along with psychotropic medications, and advanced age.[12] Researchers observed no significant difference in choking rates between men and women.[12] The estimated rates of fatal choking for adults aged 18 to 64 are at 0.1 per 100000 and 0.7 per 100000 for those over 65 years of age.[10]

Pathophysiology

Airway obstruction can occur anywhere from the pharynx to the bronchi.  Obstruction in the larynx, above the vocal cords, has a better prognosis as therapeutic maneuvers tend to be more effective than when the obstruction occurs below the larynx, which may necessitate removal by instrumentation.[13] Also, the degree of obstruction is important as a partial obstruction will still allow passage of air and may provide additional time before the patient becomes hypoxic. Spasm and edema result from airway obstruction and become more severe as time passes.  Simultaneously the patient’s efforts to expel the object decrease over time, making spontaneous expulsion of the lodged object less likely.[13] While impossible to control, the amount of air trapped in the lungs at the time of complete obstruction will affect the pressure produced by therapeutic measures, such as abdominal thrusts, to remove the object.[13]

Stridor, a variably high pitched respiratory sound, is a common physical exam finding in airway obstruction. The cause is attributed to rapid, turbulent flow through a narrow airway opening. The reduction of airflow increases the energy expended to move air across the airway, resulting in turbulent airflow and, subsequently, stridor and respiratory distress.[14] Stridor is typically heard on inspiration but can also be audible on expiration in severe obstruction. This biphasic stridor suggests severe, fixed airway obstruction at the level of the glottis, subglottis, or upper trachea.[15]

History and Physical

The approach to a choking patient should begin with an assessment of the ABCs (airway, breathing, and circulation). The clinician should focus on skin color, level of consciousness, and work of breathing, noting chest wall retractions, nasal flaring, and the use of accessory muscles.[16] A complete airway obstruction will result in respiratory failure if not recognized and treated early. Sudden onset of respiratory distress accompanied by coughing, stridor, wheezing, or gagging warrants emergent action and should illicit a high suspicion for FBAO. The choking patient may show the universal sign for an airway obstruction by grabbing his or her neck with both hands. When the patient is stable, and the clincian can obtain their history, particular attention should focus on age (either very young or elderly), intellectual or neuromuscular disability, and precipitating events such as eating or playing with toys.[16]

The classical physical exam features include stridor and hoarseness for laryngotracheal foreign bodies and unilateral wheezing and decreased breath sounds for foreign bodies in the bronchi. A pharyngeal examination should is necessary, and if there is a visible foreign body, it may be removed but avoid blind finger sweeps. The pharyngeal exam should also evaluate for other causes of stridor and respiratory distress such as epiglottis and peritonsillar abscess.[16]

While a history of sudden coughing and choking is most predictive of FBAO, providers must have a high clinical suspicion for FBAO as a significant number of patients present with no cough, stridor, or wheezes. In the absence of these physical exam findings, providers should pay particular attention to risk factors such as age or disability and chest x-ray findings of atelectasis, lung hyperinflation, or pneumonia. While the sudden onset of symptoms is most common, the diagnosis cannot be excluded based on the duration of symptoms as many patients present greater than 24 hours after foreign body aspiration.[17]

Evaluation

While the diagnosis of FBAO often has its basis on history and physical, radiographs may be useful to confirm the diagnosis but should not be used to exclude the diagnosis, as radiographs are normal in greater than 50% of tracheal foreign bodies.[17] Upright lateral and frontal radiographs of the neck are recommended for suspected upper airway obstruction, while chest inspiratory and expiratory views can be added for lower airway obstruction.[18] Because most foreign bodies are radiolucent, indirect signs of obstruction such as over-distention of the hypopharynx and prevertebral soft-tissue swelling may aid in the diagnosis. If the foreign body lodges in lower portions of the airway, chest radiographs may reveal unilateral hyperinflation, atelectasis, or mediastinal shift. Expiratory views have demonstrated to improve diagnostic accuracy as the affected lung will remain lucent, as air remains trapped distal to the foreign body.[18]

Treatment / Management

A child with a presumed airway obstruction that is still able to maintain some degree of ventilation should be allowed to clear the airway by coughing. If the child cannot cough, vocalize, or breathe, emergent steps are necessary to clear the airway. For infants under one year of age, alternating sequences of five back blows and five chest thrusts are performed until the object clears or the infant becomes unresponsive. Abdominal thrusts should not be performed in infants as their livers are more prone to injury.[19] For a choking child, over one year of age, subdiaphragmatic abdominal thrusts (i.e., the Heimlich maneuver) should be performed until clearing the object, or the child becomes unconscious. If the infant or child becomes unresponsive, immediately start chest compressions. After 30 compressions, the airway should undergo evaluation, and if a foreign body is visible, it requires removal, but blind finger sweeps should not be performed as they may push the foreign body downwards to the larynx. A series of 30 compressions and two breaths should continue until the object is expelled.[19]

The treatment for an adult with complete FBAO is similar to that of a child where a bystander performs the Heimlich maneuver until expelling the foreign body or CPR if the patient loses consciousness. If nobody is present to assist in the Heimlich maneuver, the choking individual may self-administer thrusts with his or her fist or by forcibly leaning against a firm object such as the back of a chair. For patients who are pregnant or morbidly obese, abdominal thrusts may not be feasible, and chest thrusts against the patient’s sternum may be performed.[20]

If the above described basic life support measures do not clear the obstruction, direct laryngoscopy should be performed with attempts to remove the foreign object with Magill forceps and/or suction. If the object is still causing obstruction and the clinician believes the foreign body is above the level of the vocal cords, a cricothyrotomy with trans-tracheal ventilation is appropriate. If the foreign body lodges below the level of the vocal cords, the provider may attempt endotracheal intubation with the endotracheal (ET) tube used to advance the foreign body into the right mainstem bronchus. The ET tube should then be withdrawn above the carina to allow ventilation of the left lung, and preparations should be made for bronchoscopy in the operating room.[16]

When a partial FBAO is suspected, a diagnostic bronchoscopy should be strongly considered, even in the absence of radiological findings. History of a witnessed aspiration event, physical exam findings, and radiological findings should merit consideration to determine the necessity of bronchoscopy. However, negative physical exam and radiological findings alone should not be used to rule out FBAO.  A multi-year study with 431 patients determined that despite negative physical exam and radiological findings, one-third of these patients were still found to have a foreign body by bronchoscopy.[21]

Differential Diagnosis

The differential diagnosis for a patient with stridor, respiratory distress, and cough is vast and includes FBAO. An approach to help narrow the differential is to determine the onset of symptoms and the presence of fever.[16] A sudden onset of stridor, choking, or gagging suggests a foreign body, anaphylaxis, blunt/penetrating trauma, burn injury, or angioedema. Rapid onset of symptoms in a febrile child may be epiglottis, bacterial tracheitis, retropharyngeal abscess, or peritonsillar abscess. Gradual onset of symptoms or barking cough could be attributable to viral croup. For children under six months, consider anatomical causes such as laryngotracheomalacia, vocal cord paralysis, subglottic stenosis, vascular rings, and airway hemangioma. Esophageal foreign bodies are more common than airway foreign bodies and can contribute to respiratory compromise from mass effect and inflammation. Caustic ingestions such as cleaning supplies and laundry detergent or detergent “pods” that may be ingested by toddlers can similarly present with choking.[18]

Pertinent Studies and Ongoing Trials

Given the acute nature with which foreign body airway obstructions frequently present and the subsequent need for emergent resuscitation, much of the ongoing research into this and other cardiopulmonary science is reviewed regularly by the International Liaison Committee on Resuscitation (ICOR). The ILCOR consists of members of the leading global resuscitative organizations and is engaged in an ongoing Continuous Evidence Evaluation (CEE) system for ongoing review of resuscitative science. This CEE system has replaced the previous system where resuscitative care recommendations were made on a 5-year cyclic basis. 

Prognosis

The prognosis of FBAO depends on the degree of obstruction and duration of hypoxia. Patients with partial FBAO that can clear the airway have little to no complications and can be managed based on any existing risk factors for future aspiration events. In a complete FBAO, loss of consciousness occurs in seconds to minutes. For patients requiring CPR, outcomes are particularly grim as mortality reaches 90% for out of hospital cardiac arrests, and of those who survive to hospital admission, mortality reaches 60%-70%.[22] While neurologic outcomes worsen as the duration of hypoxia increases, the prognosis is often difficult to predict. Findings that portend a worse prognosis include absent pupillary light reflex, absent corneal reflex, myoclonus status epilepticus, and malignant EEG patterns defined as burst suppression, generalized suppression, alpha coma, post-anoxic status epilepticus, or nonreactive background.[22] Because of the difficulty in predicting favorable outcomes, guidelines recommend delaying the withdrawal of life-sustaining measures until at least 72 hours following the return of spontaneous circulation (ROSC).[23]

Complications

The most feared complication of FBAO is hypoxia resulting in respiratory arrest, anoxic brain injury, and death. Long term complications of undiagnosed airway foreign bodies are atelectasis, pneumonia, or bronchiectasis, occasionally requiring lobectomy or segmentectomy. It is also not uncommon for the treatment of FBAO to have deleterious side effects. Complications of the Heimlich maneuver include injury to the abdominal or thoracic viscera and regurgitation of stomach contents. For patients requiring bronchoscopy, potential complications include bleeding, infection, airway perforation, and pneumothorax.[21]

Deterrence and Patient Education

Multiple measures reduce the risk of choking. For adults, food texture modification should be based on the sufficiency of the airway defense mechanism and cough strength.[24] Avoidance of problem foods, improving mealtime posture, adequate supervision for those at high risk for choking, proper dental care, and monitoring medication side effects are some of the frequently described recommendations for choking prevention.[12]

For children, the American Academy of Pediatrics (AAP) provides guidance for introducing solid foods to infants and recommends that pureed foods be introduced between 4 and 6 months.[25] Certain behaviors, such as walking, talking, laughing, and eating quickly, may increase a child’s risk of choking.[8] The AAP has proposed public health measures such as mandatory food labeling for foods that carry a high choking risk.[4] For non-food items, the Child Safety Protection Act requires choking-hazard warning labels for certain toys and games.

Enhancing Healthcare Team Outcomes

Complete foreign body airway obstruction is a medical emergency and requires immediate action by untrained bystanders to restore the victim's airway. The AAP recommends choking first aid and CPR training for parents, teachers, child care providers, and others who care for children.[4] Nursing home staff and those who care for the elderly would also benefit from this training. Pediatricians should continue to provide parents and caregivers guidance on appropriate food and toy selection as outlined by the AAP. While the Child Safety Protection Act requires choking hazard warning labels on certain toys in the United States, no such system exists for high-risk foods. Naturally, emergency medical staff are well-versed in dealing with such situations, and often train others. Food warning labels, a choking-incident surveillance and reporting system, and choking-prevention campaigns are some proposed legislative solutions to reduce choking incidents.[4] Outcomes will improved with an interprofessional healthcare team consisting of emergency medical technicians, triage and emergency department nurses, emergency department providers, and surgeons. [Level 5]