When faced with a potential foreign body obstruction in the upper airway or bronchus, quick and accurate diagnosis is crucial for effective management. The TMC and CSE exams often include questions about when and why to recommend a chest radiograph in such cases.
Understanding the indications for imaging, the different radiographic views available, and their diagnostic value is essential for respiratory therapists.
In this article, we will discuss when a chest radiograph should be ordered to evaluate a suspected foreign body aspiration, which imaging techniques are most useful, and how to interpret key findings that confirm or rule out an obstruction.
Take our free course to learn essential tips, insights, and strategies to pass the TMC Exam on your first (or next) attempt.
Recognizing the Need for a Chest Radiograph in Foreign Body Aspiration
Foreign body aspiration is a critical emergency that requires prompt recognition and appropriate diagnostic steps. It is most commonly seen in pediatric patients, but adults—especially those with neurological disorders, impaired swallowing, or altered consciousness—are also at risk.
Symptoms can vary based on the size, location, and nature of the foreign body. Patients may present with sudden-onset coughing, wheezing, stridor, or respiratory distress. In some cases, the obstruction may be partial, leading to persistent respiratory symptoms such as recurrent pneumonia or chronic cough.
When foreign body aspiration is suspected, a chest radiograph (X-ray) is often the first imaging study recommended. While not all aspirated objects are radiopaque (visible on X-ray), certain signs on a radiograph can suggest the presence of a foreign body. The decision to order a chest X-ray depends on the clinical presentation, with specific imaging views providing crucial diagnostic information.
Choosing the Right Imaging Modality
The type of radiographic study chosen depends on the suspected location of the foreign body:
- Anterior-Posterior (AP) and Lateral Chest Radiographs: These are commonly ordered when an obstruction in the trachea or lower airways is suspected. Radiopaque foreign bodies, such as metal or some food particles with calcium content, may be directly visible.
- Lateral Neck X-ray: If upper airway obstruction is suspected, particularly in the larynx or trachea, a lateral neck film can help visualize swelling, obstruction, or the “steeple sign” associated with conditions like croup.
- Expiratory Chest Radiograph: This is particularly useful for detecting non-radiopaque objects, which may cause air trapping. A unilateral hyperinflation of the affected lung due to a check-valve effect (air entering but not exiting) is a strong indicator of a bronchial foreign body.
- Fluoroscopy or CT Scan: In cases where initial X-rays are inconclusive but suspicion remains high, fluoroscopy or a low-dose CT scan may provide better visualization. CT is highly sensitive and can detect radiolucent objects that might not appear on standard X-rays.
Note: By selecting the appropriate imaging technique, respiratory therapists can aid in the timely diagnosis and management of airway obstructions. Recognizing radiographic findings such as hyperinflation, mediastinal shift, or signs of atelectasis can help guide further intervention, including bronchoscopy for foreign body removal.
Interpreting Radiographic Findings
Once a chest radiograph is obtained, careful evaluation of the images is necessary to identify signs of a foreign body obstruction. While radiopaque foreign bodies are directly visible, most aspirated objects—such as food particles, plastic, or organic materials—are radiolucent and may not appear on X-rays.
In these cases, indirect signs must be analyzed:
- Unilateral Hyperinflation: If the foreign body acts as a check valve, allowing air to enter but not exit the affected lung, the radiograph may show overinflation of one lung with a possible mediastinal shift toward the unaffected side. This finding is best visualized on an expiratory film.
- Atelectasis (Lung Collapse): If the obstruction is complete, the affected lung segment may appear as an area of increased radiopacity (whiteness) due to lung collapse. This may also lead to a mediastinal shift toward the affected side.
- Air Trapping on Expiratory View: A standard inspiratory chest X-ray may appear normal, but an expiratory view can reveal air trapping, which strongly suggests bronchial obstruction.
- Deviation of the Trachea or Mediastinum: If significant air trapping or lung collapse occurs, the trachea and mediastinum may shift to the opposite side.
- Soft Tissue Swelling on a Lateral Neck X-ray: If the foreign body is in the upper airway (e.g., the larynx or trachea), swelling around the obstruction may be seen. The “steeple sign” suggests subglottic narrowing, commonly seen in croup but potentially indicative of obstruction.
Next Steps in Management
If a foreign body aspiration is confirmed or highly suspected based on radiographic findings and clinical presentation, immediate intervention is required. Management options include:
- Bronchoscopy: This is the gold standard for both diagnosis and removal of a foreign body. A rigid bronchoscopy is typically performed in children, while a flexible bronchoscopy may be used in adults.
- Oxygen and Airway Support: If the patient exhibits respiratory distress, oxygen therapy or noninvasive support may be needed. In severe cases, endotracheal intubation or emergency tracheostomy may be required.
- Observation and Follow-Up: In cases where aspiration is suspected but not confirmed on imaging, patients should be monitored closely. If symptoms persist or worsen, additional imaging or bronchoscopy may be necessary.
TMC/CSE Tips for Chest X-Rays in Foreign Body Aspiration
To excel on the TMC and CSE exams, you must understand when and why a chest X-ray for suspected foreign body aspiration should be recommended.
Here are some key test-taking strategies:
Know When to Recommend Imaging
- If a patient presents with sudden-onset respiratory distress, stridor, or unilateral wheezing, suspect foreign body aspiration.
- For upper airway obstructions, recommend a lateral neck X-ray to assess for swelling or obstruction.
- For lower airway foreign bodies, recommend a chest X-ray with inspiratory and expiratory views to identify air trapping.
Recognize Indirect Signs on Imaging
- Hyperinflation on one side suggests a partial obstruction acting as a check valve.
- Atelectasis and mediastinal shift indicate a complete obstruction causing lung collapse.
- Tracheal deviation toward the affected side suggests lobar collapse.
Understand Next Steps
- If suspicion remains high despite a normal X-ray, recommend bronchoscopy, which is both diagnostic and therapeutic.
- CT scan may be required if the object is radiolucent and still suspected.
Take our free course to learn essential tips, insights, and strategies to pass the Clinical Simulation Exam (CSE) on your first (or next) attempt.
Key Takeaways
When preparing for exam questions about foreign body aspiration, keep these essential points in mind:
- Always suspect foreign body aspiration in cases of sudden-onset coughing, wheezing, or respiratory distress, especially in children.
- Understand which radiographic views are most appropriate: expiratory chest X-ray for lower airway obstruction, lateral neck X-ray for upper airway obstruction.
- Recognize indirect radiographic signs such as air trapping, hyperinflation, atelectasis, and mediastinal shift.
- Know that bronchoscopy is the definitive diagnostic and therapeutic procedure for airway foreign bodies.
Note: By mastering these concepts, you will be well-prepared to answer exam questions and manage real-life scenarios involving foreign body aspiration effectively.
Final Thoughts
Foreign body aspiration is a critical respiratory emergency that requires prompt recognition and appropriate diagnostic imaging. While chest radiographs may not always show the foreign body itself, they can provide crucial indirect signs such as hyperinflation, air trapping, or atelectasis that indicate obstruction.
Choosing the right imaging modality—whether an expiratory chest X-ray, lateral neck radiograph, or CT scan—can aid in early detection and guide appropriate intervention. As a respiratory therapist, understanding when to recommend a chest radiograph and how to interpret key findings is essential for both the TMC and CSE exams, as well as real-world clinical practice.
Mastering these concepts will ensure that you are well-equipped to assist in the rapid diagnosis and management of airway obstructions, ultimately improving patient outcomes.
Written by:
John Landry is a registered respiratory therapist from Memphis, TN, and has a bachelor's degree in kinesiology. He enjoys using evidence-based research to help others breathe easier and live a healthier life.
References
- Cramer N, Jabbour N, Tavarez MM, et al. Foreign Body Aspiration. [Updated 2023 Jul 31]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2025.