Chest Radiography in Asthma: Indications and Findings
Chest radiography is usually appropriate for complicated asthma exacerbations (positive physical examination, abnormal vital signs, or risk factors for poor outcome) but may be appropriate for uncomplicated exacerbations depending on clinical concerns—the primary goal is detecting life-threatening complications like pneumothorax, which causes 27% of deaths in acute exacerbations. 1
When to Obtain Chest Radiography
Complicated Asthma Exacerbations (Usually Appropriate)
Obtain chest radiography when patients present with:
- Abnormal vital signs (tachycardia >160, respiratory rate >60, fever)
- Positive physical examination findings (localized rales, localized decreased breath sounds, localized wheezing)
- Status asthmaticus requiring hospital admission
- Unresponsiveness to bronchodilator therapy
- Organic brain disease or inability to reliably follow-up
- Other risk factors for poor outcome 1, 2
Clinical Pearl: Pneumothorax occurs in 0.5-2.5% of admitted status asthmaticus patients and was the direct cause of death in 27% of acute exacerbation fatalities in one series 1. Chest radiography is highly effective for screening pneumothorax and pneumomediastinum 1.
Uncomplicated Asthma Exacerbations (May Be Appropriate)
For patients with negative physical examination, normal vital signs, and no risk factors, chest radiography may be appropriate depending on:
- Provider's clinical concerns
- Patient's reliability for follow-up
- Severity requiring hospitalization 1
Important Context: The incidence of pneumonia in uncomplicated asthma exacerbation is exceedingly low (<2% show pneumonic opacities) 1. However, in hospitalized adults with acute asthma, clinically significant radiographic abnormalities occur in approximately 15% 3.
Typical Radiographic Findings
Normal or Minimal Changes (Most Common)
- 52.9% have completely normal radiographs 3
- 31.8% show features compatible with obstructive lung disease:
Complications Requiring Management (8.2%)
- Pneumothorax (0.5-2.5% in status asthmaticus)
- Pneumomediastinum
- Focal parenchymal opacities/pneumonia
- Segmental or greater atelectasis 3
Important Incidental Findings (6.7%)
- Tuberculosis
- Heart failure/pulmonary vascular congestion
- Bronchial neoplasm
- Enlarged cardiac silhouette
- New solitary pulmonary nodule 3, 5
Clinical Decision Algorithm
For adults admitted with acute asthma:
- Assess vital signs and perform focused physical examination
- If ANY of the following present → Obtain chest radiograph:
- Tachycardia, tachypnea, fever
- Localized rales, decreased breath sounds, or wheezing
- Failed bronchodilator therapy requiring admission
- Status asthmaticus
- If completely uncomplicated → Consider chest radiograph based on ability to follow-up and clinical judgment
For emergency department presentations:
- Adults: Only 2.2% have abnormal radiographs unless unresponsive to bronchodilators and requiring admission 6
- Children: 13% have abnormal radiographs; obtain if rales and rhonchi present in addition to wheezing 6
Advanced Imaging Considerations
CT chest without IV contrast may be warranted if:
- Chest radiograph is negative or equivocal AND
- Patient cannot reliably follow-up OR
- Any delay in diagnosis could be life-threatening 1
Note: CT, MRI, ultrasound, and CTA have no role in initial imaging of uncomplicated asthma exacerbations 1
Key Pitfalls to Avoid
- Don't skip radiography in hospitalized adults: 34% have major radiographic abnormalities that alter management, independent of fever or leukocytosis 5
- Don't rely solely on clinical examination: 9% of severe acute asthma patients have pulmonary collapse or consolidation not detected clinically 4
- Anteroposterior views are adequate for interpretation in acute settings 4
- Antibiotic use correlates with radiographic focal opacities or infiltrates, even in afebrile patients, not with elevated white blood cell count alone 5