Diagnostic Approach to ARDS with Clinical Deterioration

Differential Diagnosis and Diagnostic Evaluation

The American Thoracic Society recommends considering alternative diagnoses, such as acute interstitial pneumonia, organizing pneumonia, and acute eosinophilic pneumonia, in patients with ARDS who deteriorate despite broad-spectrum antibiotics 1
Bronchoscopy with bronchoalveolar lavage (BAL) has a 41% diagnostic yield in identifying treatable conditions, including Legionella, anaerobes, resistant pathogens, tuberculosis, fungi, and Pneumocystis, and should be performed immediately in patients with treatment failure 1
BAL fluid should be sent for bacterial culture, fungal culture, viral PCR, Pneumocystis staining, and cell differential to identify organisms and guide specific therapy 1
A detailed exposure and medication history, including substance use, vaping, and recreational drugs, should be obtained to identify potential causes of ARDS-mimics 1
Systemic disease evaluation, including connective tissue disease markers and vasculitis markers, should be performed to identify underlying conditions that may be contributing to ARDS 5

Bronchoscopy with BAL can identify organisms even in patients receiving antibiotics when recovered at high concentrations 2
Transbronchial biopsy should be considered for atypical lesions 3, 4

CT chest with contrast can separate pleural fluid from parenchymal disease and demonstrate parenchymal abscesses, and can help distinguish focal pneumonia from diffuse ARDS 2
CT chest with contrast may reveal patterns suggestive of organizing pneumonia, hypersensitivity pneumonitis, or pulmonary hemorrhage 1

If an inflammatory/autoimmune mimic is identified, methylprednisolone should be increased to 2 mg/kg/day IV, and continued for 2-3 days, then tapered slowly over 4-6 weeks 3, 4
If an infectious mimic is identified, pathogen-specific antimicrobial therapy should be initiated immediately 1
If a drug/chemical-induced disease is identified, the offending agent should be withdrawn immediately, and corticosteroids considered 1

Mechanical ventilation strategy should include low tidal volume ventilation (4-6 mL/kg ideal body weight) and appropriate PEEP 7
Fluid management should be conservative, with vasoactive drugs used to improve microcirculation 7
Infection prophylaxis, including prophylactic antibiotics for Pneumocystis pneumonia, should be considered for patients receiving prolonged steroid therapy 3
Monitoring for steroid complications, including hyperglycemia, should be performed regularly 3