What are the diagnostic criteria for Acute Respiratory Distress Syndrome (ARDS) in pediatric patients?

Pediatric ARDS Diagnostic Criteria

Pediatric ARDS (PARDS) is diagnosed when a child presents with acute onset (within 7 days of a known clinical insult), bilateral chest infiltrates, respiratory failure not explained by cardiac failure or fluid overload, and hypoxemia defined by specific oxygenation thresholds that differ from adult criteria. 1, 2

Core Diagnostic Requirements

All four components must be present simultaneously for PARDS diagnosis:

1. Timing

• Acute onset within 7 days of a known clinical insult or new/worsening respiratory symptoms 1

2. Chest Imaging

• Bilateral opacities on chest radiograph or CT scan 3
• Infiltrates not fully explained by effusions, lobar/lung collapse, or nodules 3
• Lung ultrasound shows bilateral diffuse areas of reduced lung aeration with interstitial syndrome, consolidations, pleural line abnormalities, and possible pleural effusion 4

3. Origin of Edema

• Respiratory failure not fully explained by cardiac failure or fluid overload 3
• Echocardiography should be performed if no clear ARDS risk factor exists to exclude cardiogenic pulmonary edema 3

4. Oxygenation Criteria (Pediatric-Specific)

The key difference in pediatric patients is the use of Oxygenation Index (OI) as an alternative to PaO₂/FiO₂ ratio:

Option A: PaO₂/FiO₂ Ratio (with minimum PEEP 5 cmH₂O)

• Mild PARDS: 200 mmHg < PaO₂/FiO₂ ≤ 300 mmHg 5
• Moderate PARDS: 100 mmHg < PaO₂/FiO₂ ≤ 200 mmHg 5
• Severe PARDS: PaO₂/FiO₂ ≤ 100 mmHg 5

Option B: Oxygenation Index

• Used when arterial blood gas available and patient on mechanical ventilation 1
• OI = (Mean Airway Pressure × FiO₂ × 100) / PaO₂ 6
• Higher OI values indicate more severe disease 6

Essential Diagnostic Workup

Mandatory Tests

• Arterial blood gas: Required to determine PaO₂/FiO₂ ratio and assess for metabolic or respiratory acidosis 3
• Chest radiograph or CT: Necessary to document bilateral opacities 3

Recommended Additional Testing

• Echocardiography: Perform when no clear ARDS risk factor exists to exclude cardiogenic causes 3
• Lung ultrasound: Useful for semi-quantitative evaluation of lung aeration and can help guide respiratory interventions 4

Common Predisposing Factors in Children

The most frequent insults leading to PARDS include:

• Sepsis and pneumonias 6
• Major trauma and shock 6
• Aspiration and near drowning 6
• Burns and envenomation 6
• Meconium aspiration syndrome in neonates (now recognized as a cause of neonatal ARDS) 4

Critical Pitfalls to Avoid

Ventilator Settings During Assessment

• Always calculate PaO₂/FiO₂ ratio with patients on at least 5 cmH₂O of PEEP 5
• Failure to use minimum PEEP requirements will lead to misclassification of severity 5

Differential Diagnosis Challenges

• Diffuse interstitial lung diseases, diffuse pulmonary infections, and drug-induced lung injury can present identically to ARDS 3
• These conditions may require specific treatments rather than standard ARDS management 3
• Cardiogenic pulmonary edema must be actively excluded through clinical assessment and echocardiography 3

Prognostic Indicators

• PaO₂/FiO₂ ratio, alveolar-arterial oxygen difference (A-aDO₂), and ventilation index on the second day after diagnosis are valuable predictors of mortality 6
• Early identification of poor prognostic indicators may allow for timely escalation of therapy 6

Lung Ultrasound Findings (Adjunctive Tool)

While not yet included in formal diagnostic criteria, lung ultrasound demonstrates high utility:

• Bilateral diffuse areas of reduced lung aeration 4
• Areas of interstitial syndrome and consolidations 4
• Pleural line abnormalities 4
• Possible pleural effusion 4
• Can be used to semi-quantitatively measure effects of fluid restriction, alveolar recruitment, and surfactant administration 4