How to Assess Stridor: A Comprehensive Guide for Healthcare Professionals

Stridor is a high-pitched, wheezing sound caused by disrupted airflow, typically due to an obstruction in the upper airway. It's a critical sign that can indicate potentially life-threatening conditions. For medical students and healthcare professionals, the ability to accurately assess stridor is essential. This guide will cover the fundamental aspects of stridor assessment, from understanding its underlying causes to mastering the physical examination and diagnostic approaches.

Understanding Stridor: Types and Causes

Stridor can be classified into different types based on its timing during the respiratory cycle, which provides clues to the location and nature of the airway obstruction.

1. Inspiratory Stridor

Description: Occurs during inhalation and is often heard over the larynx or trachea.

Common Causes:

Laryngomalacia: The most common cause in infants, where the soft, immature cartilage of the upper larynx collapses inward during inhalation.

Epiglottitis: Inflammation of the epiglottis, often due to bacterial infection, leading to severe airway obstruction.

Croup: Viral infection causing swelling of the larynx and trachea, commonly in children.

Vocal cord paralysis: Unilateral or bilateral paralysis can cause a partial obstruction, leading to inspiratory stridor.

2. Expiratory Stridor

Description: Occurs during exhalation and typically indicates an obstruction in the lower trachea or bronchi.

Common Causes:

Tracheomalacia: Weakness in the tracheal walls leading to collapse during expiration.

Bronchomalacia: Similar to tracheomalacia but occurring in the bronchi, causing airway narrowing during exhalation.

Foreign body aspiration: An object lodged in the lower airway can cause expiratory stridor.

3. Biphasic Stridor

Description: Present during both inspiration and expiration, suggesting a fixed obstruction at the level of the glottis or subglottis.

Common Causes:

Subglottic stenosis: Narrowing of the space below the vocal cords, often due to prolonged intubation or congenital anomalies.

Laryngeal tumors: Benign or malignant growths in the larynx can cause a constant obstruction.

Bilateral vocal cord paralysis: Both vocal cords are paralyzed, leading to significant airway compromise.

Clinical Assessment of Stridor

Assessing stridor requires a thorough clinical examination, which includes history-taking, physical examination, and possibly advanced diagnostic procedures.

1. History-Taking

Understanding the patient's history is crucial in determining the cause of stridor. Key questions to ask include:

Onset: Did the stridor develop suddenly or gradually?

Sudden onset may indicate foreign body aspiration or acute epiglottitis.

Gradual onset suggests chronic conditions like laryngomalacia or subglottic stenosis.

Associated Symptoms: Are there symptoms like fever, drooling, or difficulty swallowing?

Fever and drooling are red flags for epiglottitis.

Difficulty swallowing could indicate a mass or foreign body.

Previous Medical History: Is there a history of recent illness, surgery, or intubation?

Recent upper respiratory infections point toward croup.

Intubation history raises suspicion for subglottic stenosis.

Age of the Patient: Pediatric stridor has different causes than adult stridor.

In infants, laryngomalacia is common.

In adults, vocal cord paralysis or tumors are more likely.

2. Physical Examination

A comprehensive physical examination is essential for evaluating stridor. It involves inspection, auscultation, palpation, and potentially more advanced techniques.

Inspection

Observation of Breathing Patterns: Watch for signs of respiratory distress, such as nasal flaring, retractions, or use of accessory muscles.

Color of the Skin: Cyanosis indicates severe hypoxia and urgent airway compromise.

Neck Position: A hyperextended neck may suggest that the patient is trying to maximize airway patency.

Auscultation

Location of Stridor: Listen to the neck and chest to determine if the stridor is inspiratory, expiratory, or biphasic.

Inspiratory stridor suggests upper airway obstruction.

Expiratory stridor suggests lower airway obstruction.

Severity of Stridor: Mild stridor may be heard only with a stethoscope, while severe stridor is audible without a stethoscope.

Palpation

Tracheal Deviation: Palpate the trachea for any deviation, which might indicate a mass or pneumothorax.

Thyroid Gland: Enlargement of the thyroid can cause compressive symptoms leading to stridor.

Lymph Nodes: Enlarged lymph nodes could suggest malignancy or infection.

3. Advanced Diagnostic Techniques

Flexible Laryngoscopy

Indication: Performed when the cause of stridor is unclear after a physical exam.

Procedure: A flexible scope is passed through the nose to visualize the larynx, vocal cords, and upper trachea.

Findings: This can identify laryngomalacia, vocal cord paralysis, tumors, or foreign bodies.

Imaging Studies

X-rays: Lateral neck X-rays can reveal conditions like epiglottitis (thumb sign) or foreign body.

CT Scans: Useful for evaluating deeper structures and assessing masses, stenosis, or tracheomalacia.

MRI: Provides detailed images of soft tissues and is useful in evaluating tumors or vascular abnormalities causing stridor.

Bronchoscopy

Indication: If a foreign body is suspected or if there is a need for detailed visualization of the trachea and bronchi.

Procedure: A bronchoscope is passed into the trachea and bronchi to directly observe and possibly retrieve a foreign body or biopsy a lesion.

Findings: Can confirm diagnoses like foreign body aspiration, bronchomalacia, or tumors.

Management of Stridor

The management of stridor depends on its underlying cause and severity. Immediate airway management is critical in severe cases, while chronic conditions may require ongoing monitoring and intervention.

1. Emergency Management

Airway Stabilization: In cases of severe airway obstruction (e.g., epiglottitis or foreign body aspiration), securing the airway is the top priority.

Endotracheal Intubation: May be necessary to maintain airway patency.

Tracheostomy: In cases where intubation is not possible or fails, a tracheostomy may be required.

Pharmacological Treatment:

Epinephrine: Nebulized epinephrine can reduce airway swelling in conditions like croup.

Corticosteroids: Used to reduce inflammation in cases of croup or subglottic stenosis.

2. Long-Term Management

Surgical Intervention: Some conditions, such as subglottic stenosis or laryngeal tumors, may require surgical correction.

Laser Surgery: For removing benign laryngeal lesions.

Tracheal Reconstruction: In cases of severe tracheomalacia or stenosis.

Speech Therapy: For patients with vocal cord paralysis, speech therapy can help improve voice and breathing.

Monitoring and Follow-Up: Regular follow-up with a specialist is essential for chronic conditions like laryngomalacia or vocal cord paralysis.

3. Patient Education and Support

Educating Patients and Families: Ensuring that patients and their families understand the nature of stridor, its causes, and the importance of seeking immediate care if symptoms worsen.

Support Groups: For chronic conditions, support groups can provide emotional support and practical advice for managing stridor.

Conclusion

Assessing stridor is a critical skill for medical students and healthcare professionals, as it can be a sign of serious underlying conditions that require prompt attention. By understanding the different types of stridor, conducting a thorough clinical assessment, and utilizing appropriate diagnostic tools, clinicians can make accurate diagnoses and provide effective treatment.