Patients suspected of having ARDS on the basis of CXR findings and ventilator settings should have theirdiagnosis confirmed by following the below guidance.

1. Verify that the patient is likely to have respiratory failure from either a direct or indirect pulmonary injury or the need for mechanical ventilation support.
2. Consider diagnoses which can mimic ARDS as described above.
3. Obtain a good quality anteroposterior upright CXR and look for diffuse infiltrates. Consider a chest CT if this imaging modality is available and the patient is stable for transport to CT.
4. If cardiogenic pulmonary edema and/or fluid overload cannot be fully excluded as the cause of or a contributing factor to the patient’s respiratory failure, consider placing a central venous pressure catheter and obtain a trans-thoracic echocardiogram if possible.11,12
5. Place the patient on volume- or pressure-control ventilation.

a. Tidal volume (VT) approximately 6-8 mL/kg using Predicted Body Weight (PBW), see ARDSNet Card inAppendix B) targeting a plateau pressure (PPLAT) ≤ 30 cm H2O or if using a pressure control mode of ventilation, set the inspiratory pressure to 30-35 cm H2O and then decrease it gradually to achieve aVT of 6-8 mL/kg.

b. Set the respiratory rate between 6 and 35 and adjust to achieve a pH≥7.3.

c. Set PEEP (minimum 5 cm H2O) and FiO2 according to the ARDSNet table 23 to achieve a SpO2 of 88-95% (PaO2 of 55-80 mmHg). Allow the patient’s gas exchange to equilibrate for 30 minutes and then draw an ABG to calculate the patient’s P:F ratio.

If ARDS is confirmed, document the grade (mild, moderate, severe) in the patient’s record with the diagnostic criteria used. A recent study further demonstrated that Age-Adjusted Oxygenation Index (AOI) accurately predicts prognosis in patients with ARDS.13 Traditionally, the Oxygenation Index (OI) is calculated as where MAPis mean airway pressure. This study relied on the ARDSNet database which recorded PPLAT rather than MAP; so the AOI was calculated as (100 X PPLAT / P:F)+Age . These authors found that an AOI of 80-99 in the first four days of ARDS was associated with 50% mortality.

Pediatric trauma patients are also at risk for development of ARDS.14 While there are many similarities in thepathophysiology of ARDS in adults and children, recent literature has supported a slightly different approachwith the diagnostic criteria used in pediatric ARDS.15,16 Similar to the Berlin criteria for adults, ARDS in childrenrequires respiratory failure not explained by cardiac failure or volume overload. However, instead of utilizationof a P:F ratio, recent recommendations have been made to utilize OI to grade severity of ARDS in the pediatricpopulation. As above, OI can be calculated as (100 X PPLAT / P:F). Mild ARDS can be defined as an OI of 4 to <8, moderateARDS defined as an OI of 8 to <16 and severe ARDS defined as an OI ≥16. 15,16