A patient presents with expiratory crepitations on lung exam; what are the possible causes and what is the recommended initial evaluation and management?

Expiratory Crackles: Causes and Clinical Approach

Expiratory crackles are most commonly caused by sudden airway closure during expiration and should prompt evaluation for COPD, heart failure, pneumonia, or central airway collapse, with chest radiography as the initial imaging study followed by spirometry to establish the diagnosis.

Mechanism of Expiratory Crackles

Expiratory crackles are generated by sudden airway closure events during expiration, which are mechanistically opposite to the explosive airway opening that produces inspiratory crackles 1. These sounds are:

• Less numerous than inspiratory crackles (approximately half as many) 1
• Associated with positive polarity in 69% of cases, compared to predominantly negative polarity in inspiratory crackles 1
• Characterized by progressively decreasing pitch during expiration in 72% of patients 2

Primary Differential Diagnosis

COPD (Most Common)

COPD is the leading cause of expiratory crackles in adults and requires spirometry for definitive diagnosis. 3

• Diagnosis requires FEV1 <80% predicted and FEV1/VC ratio <70% that does not change markedly over several months 3
• Expiratory crackles in COPD reflect small airway dysfunction and dynamic airway collapse 3
• Patients with acute exacerbations show significantly more crackles and wheezes at posterior chest locations compared to stable disease 4
• Physical examination may reveal quiet breath sounds, prolonged expiratory duration, and weight loss as disease progresses 3

Heart Failure

Congestive heart failure presents with expiratory crackles due to cardiogenic pulmonary edema 3. Key distinguishing features include:

• B-natriuretic peptide measurement and echocardiography are essential to distinguish cardiac from pulmonary dyspnea 3
• Crackles in heart failure patients show similar spectral and temporal characteristics to those in pneumonia and interstitial fibrosis 1

Pneumonia

Acute infection causes expiratory crackles through inflammatory airway changes 2, 1:

• Crackles are typically more numerous and widespread than in stable chronic conditions 4
• Clinical context (fever, acute onset, productive cough) helps differentiate from chronic causes

Central Airway Collapse (Often Missed)

Expiratory central airway collapse is an underdiagnosed condition that mimics asthma and COPD and should be considered when standard treatments fail. 5

• Presents with dyspnea, cough, sputum production, and recurrent respiratory infections 5
• Can coexist with asthma, COPD, and bronchiectasis 5
• Tracheomalacia/bronchomalacia may be present in up to 10% of symptomatic patients undergoing bronchoscopy 6

Initial Evaluation Algorithm

Step 1: Clinical Assessment

Document specific features 3:

• Smoking history (most COPD cases are tobacco-related) 3
• Exercise tolerance to monitor breathlessness progression 3
• Symptom pattern: chronic progressive vs. acute onset
• Associated symptoms: peripheral edema (heart failure), fever (infection), wheeze (COPD/asthma)

Step 2: Initial Imaging

Chest radiography is the appropriate initial imaging study 3:

• Excludes other pathologies but cannot positively diagnose COPD 3
• May be normal in early COPD 3
• Identifies cardiomegaly, pulmonary edema, or infiltrates

Step 3: Spirometry (Essential)

Spirometry is mandatory to establish COPD diagnosis and cannot be replaced by clinical assessment alone 3:

• Perform pre- and post-bronchodilator testing 3
• A positive response is FEV1 increase by 200 ml AND 15% of baseline 3
• Serial peak flow recordings over one week can confirm absence of variability if spirometry unavailable 3

Step 4: Advanced Evaluation When Indicated

CT chest with IV contrast is first-line for suspected tracheal deformities or when diagnosis remains unclear 3, 6:

• Dynamic expiratory CT can detect central airway collapse 6, 7
• Identifies emphysema distribution, bronchial wall thickening, and gas trapping 3

Bronchoscopy for persistent symptoms despite appropriate treatment 6, 5:

• Essential for direct visualization of dynamic airway collapse 7, 5
• Particularly important when tracheomalacia or central airway collapse is suspected 6

Critical Pitfalls to Avoid

1. Do not rely on clinical examination alone - COPD diagnosis requires objective spirometric confirmation 3

2. Beware of bronchodilator use in airway malacia - Beta-agonists may worsen dynamic airway collapse by relaxing central airway smooth muscle 7

3. Consider central airway collapse when standard treatments fail - This condition is frequently misdiagnosed as asthma or COPD 6, 5

4. Recognize multifactorial causes - More than 30% of chronic dyspnea cases have multiple contributing factors 3

5. Posterior chest auscultation is critical - Crackles and wheezes are significantly more frequent at posterior chest locations in COPD exacerbations 4

Management Considerations

For COPD with expiratory crackles 3:

• Mild disease: Short-acting β2-agonist or inhaled anticholinergic as needed
• Moderate disease: Regular bronchodilator therapy; consider corticosteroid trial (30 mg prednisolone daily for two weeks with objective spirometric endpoints)
• Severe disease: Assess arterial blood gases to identify hypoxemia/hypercapnia

For suspected central airway collapse 7, 5:

• CPAP immediately decreases respiratory distress and improves airway patency
• Tracheobronchial stenting for symptomatic cases, often as trial before definitive surgery
• Tracheobronchoplasty is definitive treatment after successful stent trial