Foreign Body Aspiration
Episode 29 focuses on foreign body aspiration, a life-threatening phenomenon that is more common in young children. Join us to learn about this important Pediatric Otolaryngology topic - we will review epidemiology, presentation, investigations, treatment, and prevention, and also review some airway anatomy!
Show Notes
Introduction
Hi Listeners! Welcome to The Oto Approach, a podcast created by medical students for medical students, to teach you about all things otolaryngology. I am your host, Alison, and today we are going to talk about Foreign Body Aspiration.
Basics and Prevalence:
Foreign body aspiration is when an object is inhaled into the respiratory tract and trapped there [1]. This is a life-threatening phenomenon that is more common in children, especially those under the age of three [1]. Specifically, 80% of foreign body aspirations occur in patients under three years old and foreign body aspiration is the fourth most common cause of death for toddlers [1]. Patients with developmental disabilities or physiologic/anatomic abnormalities of the respiratory tract are also at higher risk of aspirating foreign bodies [2].
Foreign body aspiration is a particularly important phenomenon to recognize as 2.5% of incidents result in death, whether that be from acute asphyxiation, hypoxia, respiratory failure or more chronic phenomenon from a missed diagnosis [3].
Etiology
As discussed, young children and infants are at a higher risk of foreign body aspiration, with most episodes involving pediatric patients under two years of age [1,4]. This is due to a myriad of reasons. First, as you may guess, patients of this age tend to “explore the world with their mouths”, putting everything they can get their hands on into their mouths – including small objects that can easily get trapped in the respiratory tract [1]. Additionally, young children and infants do not yet have molars in the posterior aspect of their mouths, making it easy for small items or unchewed food to slip back into their pharynx and down their airway [1].
Toddlers tend to be energetic, engaging in high activity while eating and being easily distracted by things while chewing and swallowing their food [5]. This, along with an uncoordinated swallow more common in early life, means that food can slip down into their airways when the epiglottis is not properly protecting it [1,5].
Foreign body aspiration can be particularly deadly in young patients as their airways have smaller radii, meaning that smaller objects can more fully occlude it, disrupting ventilation and leading to death [6].
Anatomy
Airway anatomy is particularly important to appreciate the mechanism of foreign body aspiration and airway occlusion, as symptoms and severity depend on the location of the foreign body [3].
Let’s review some basic airway anatomy:
The airway starts at the nose and mouth, and air is inhaled through them down the pharynx, or throat, and into the larynx, or voice box [7]. The larynx lies just anterior to the esophagus and is protected by the epiglottis during swallowing [7]. Air flows through the larynx into the trachea, which divides into the left and right main bronchi at the level of the sternal angle [7,8]. The point at which the trachea splits is called the carina [8]. The right main bronchus descends at a steeper angle than the left, which has to accommodate for the heart and associated structures – keep this in mind [8]! It will be relevant to the clinical pearls discussed at the end of the episode.
The main bronchi divide into secondary lobar bronchi, which divide into tertiary segmental bronchi [8]. Conducting bronchioles branch off of the segmental bronchi to form terminal bronchioles [7,8]. Bronchioles, unlike the rest of the airway discussed thus far, lack cartilage and end in alveoli, outpockets of the lung that facilitate gas exchange, or respiration [7,8].
Foreign bodies in the upper airways are more immediately life-threatening as they can acutely disrupt or fully prevent ventilation, preventing the inhalation of air into the lungs and exhalation of air out of the lungs [1,9].
Contrastingly, foreign bodies in the lower airways may go undetected for some time [9]. This is because the foreign body will only prevent respiration at the alveoli distal to its location, allowing other alveoli to continue gas exchange.
History
The presentation for foreign body aspiration is widely varied.
Children with upper airway compromise or more complete airway obstruction will present with acute respiratory distress, including choking, cyanosis [1]. The patient may grab at their throat, be unable to cough or speak, and you may hear high-pitched squeaks as they try to pass air through the blocked passage [10].
More distal airway obstruction may present with a sudden onset of wheezing, cough, and dyspnea [1,11]. Note that up to 20% of aspirations may be unwitnessed, so it is important to keep in your differential despite not having the story of a patient choking or putting small objects in their mouths [12].
Patients with longstanding undetected airway foreign bodies may present with recurrent pneumonia, hemoptysis, failure to thrive or a misdiagnosis of asthma unresponsive to treatment [2,11,13].
Physical
On physical exam, the patient may have asymmetric breath sounds (with decreased air entry on the side of the foreign body), cyanosis, and unilateral wheeze [14].
Patient Work-up and Investigations
Clinical suspicion of foreign body aspiration should be high despite a normal physical exam, as wheezes may only be heard in 60% of patients with airway foreign bodies and asymmetric breath sounds are only heard 32% of the time [1,15]. Missing a diagnosis of foreign body aspiration and thus delaying treatment can lead to increased patient suffering, as they are at risk of developing obstructive emphysema, recurrent pneumonias, bronchiectasis, lung abscesses, pneumothorax, direct bronchial injury, bronchial stenosis, failure to thrive, and even hypoxic brain injury [1,13].
Stable patients with suspected foreign body aspiration are often sent for PA, lateral, inspiratory, and expiratory chest x-rays, which can show signs of FBA such as atelectasis, air trapping resulting in unilateral hyperinflation, mediastinal shift, and consolidation [1,11,13]. The CXR may also show the foreign body itself if it is radiopaque [1]. That said, 30-50% of chest x-rays in foreign body aspiration are normal.[16].
Foreign body aspiration cannot often reliably be diagnosed by history or physical exam findings, and given that chest x-rays can be normal, the foreign body often needs to be directly visualized on bronchoscopy for definitive diagnosis in cases warranting a high index of suspicion [1,11,14,16].
Treatment
As well as for definitive diagnosis, bronchoscopy is used to treat foreign body aspiration by removing the offending object or particle [13,14]. It has a diagnostic accuracy of about 95% and a successful foreign body retrieval rate of over 97% [17,18].
Rigid bronchoscopes are long metal tubes inserted into the patient’s airway for the purposes of visual diagnostics and intervention [19,20]. Bronchoscopies have the added challenge of a shared airway, meaning that the anesthesiologist ventilates the patient while the otolaryngologist needs to do the procedure in the same place. The distal end of the bronchoscope (inserted deepest in the patient’s airway) has holes along the side to allow for ventilation of the contralateral lung (while the ipsilateral lung is ventilated via the main bronchoscope tube) [19].
The proximal end of the bronchoscope (closest to the patient's oral cavity) has ports for ventilation (where the oxygen supply is attached), instrumentation (for interventions), and the main opening is used for direct or camera visualization [19].
Bronchoscopy is performed in the operating room under general anesthesia [19 ]. The patient is placed supine with their neck extended into the sniffing position [19]. The bronchoscope is inserted through the oral cavity and past the uvula until you can see the epiglottis [19]. The bronchoscope is then inserted further posterior to the epiglottis, which is lifted up so you should be able to see the vocal cords [19]. To prevent damage to the cords, the bronchoscope is rotated 90º, inserted past the cords, then turned 90º back to its original position [19,21]. This allows the smallest diameter of the scope to pass through the small glottis [19,21].
At this point, ventilation is started [21]. The trachea, carina, and each main bronchus is visualized [19,21]. When entering the right bronchus, the patient’s head is turned left, and when entering the left bronchus, the patient’s head is turned right [19,21].
If the foreign body cannot yet be seen, a flexible bronchoscope may need to be inserted through the rigid bronchoscope. The flexible bronchoscope is smaller, and in keeping with its name, more flexible, so it can more seamlessly explore the distal airway, which has more turns and a smaller diameter [22].
When the foreign body is located, if it is safe to do so, grasping forceps are inserted through the instrument port of the rigid bronchoscope and used to remove the foreign body [19].
Risks of bronchoscopy include airway edema, injury to associated organs, bronchospasm, laryngospasm, and transient hypoxia [11,19,22].
Prevention
Given these risks associated with foreign body aspiration in children, it is important that otolaryngologists educate their patients on how to prevent such events.
Any small object that a child can place in their mouth has the potential to be aspirated. Ensuring a young child does not have access to small toys or other small objects goes a long way in preventing foreign body aspiration [2].
Common offenders of food aspiration include peanuts, seeds, and round fruits [1]. To avoid food aspiration, mealtimes should be distraction-free, and the child should be seated while eating [5]. Cutting fruits and other small snacks into more angular shapes (for example, cutting grapes in half or quarters) can decrease the risk of aspiration as edges catch on the teeth to stop the piece from slipping down into the trachea [1,5].
Clinical Pearls
As discussed in the anatomy section of the episode, the trachea divides into the right and left main bronchi [7,8]. The right main bronchus is wider and descends more vertically down into the thoracic cavity, whereas the left main bronchus travels to the left to accommodate the heart [8]. Additionally, the carina is often centred slightly to the left of the mid-thorax in most adults [23]. This means that if a foreign body is aspirated in an adult, it is more likely to travel directly down the right main bronchus, as this pathway is more direct than the angled direction of the left main bronchus [7,23]. In young children, like those under age 2 to 3, the tendency for a foreign body to travel down either main bronchus has been widely debated, some sources citing increased probability for the right bronchus, and others finding no difference in frequency between the two sides [4,23]. That said, most studies seem to support a slight predominance for a foreign body to lodge in the right lung, which becomes more established with age [4,23]. Why would this be? Like adults, the right main bronchus of children is wider and its angle is more vertical compared to the left, making foreign bodies more likely to travel down this route [23]. That said, the tendency for the carina to be positioned farther to the left is something that is seen more often in older children, above the age of 3 years [23]. This may be the anatomical variation accounting for the weaker preference for the right lung that becomes more prominent with age.
Patients with foreign bodies trapped in their upper airways present like an acute choking episode – significant respiratory distress, audible or visible choking, and cyanosis [1]. Similar to the classic phrase we use in croup, another upper respiratory tract condition, DO NOT AGITATE THE PATIENT. They need immediate transfer to the OR for a safe bronchoscopy [1].
The type of foreign body can alter the patient’s presentation! Inorganic foreign bodies (like beads, clips, or small toys) don’t tend to produce much airway inflammation, so they can go undetected for a long time [13]. Contrastingly, organic foreign bodies, such as nuts or small chunks of food, tend to produce more inflammation in the lung parenchyma and thus result in more complications [13]. The inflammatory reaction can cause the organic foreign body to swell, resulting in even further obstruction [1]. The most dangerous type of airway foreign body is a button battery, which can erode the respiratory mucosa, causing local necrosis and even perforation [24].
Closing Remarks
Thank you for listening to this episode of The Oto Approach. The script was developed by myself, Alison Walsh, and kindly edited by Dr. Hannah Brennan. Show notes can be found at www.theotoapproach.com, where you can also sign up for our newsletter and learn more about the team.
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