Diagnostic evaluation for patients with suspected ARDS

ARDS: acute respiratory distress syndrome; ABG: arterial blood gas; PaO₂: arterial oxygen tension; FiO₂: fraction of inspired oxygen; PEEP: positive end-expiratory pressure; DAH: diffuse alveolar hemorrhage; AEP: acute eosinophilic pneumonia; BNP: brain natriuretic peptide; CT: computed tomography.
* Although the PaO₂:FiO₂ ratio can be calculated at this point to facilitate the diagnosis of ARDS, it is most accurate when patients are mechanically ventilated.
¶ Even subtle opacities may indicate the onset of ARDS.
Δ Early recognition of ARDS is critical for the diagnosis so that supportive interventions including oxygenation and mechanical ventilation may be instituted early. Thus, monitoring those at risk helps identify ARDS at an early time point.
◊ Several conditions other than cardiogenic pulmonary edema can mimic ARDS including diffuse alveolar hemorrhage, inflammatory or autoimmune conditions (eg, acute eosinophilic pneumonia, pulmonary vasculitis, cryptogenic organizing pneumonia, acute interstitial pneumonitis, acute fibrinous organizing pneumonia), disseminated malignancy, and rare embolic syndromes such as fat or amniotic fluid embolism syndrome.
§ In most cases considerable clinical judgement is needed and most clinicians arrive at a clinically confident diagnosis of ARDS without having to pursue extensive investigations to rule out pulmonary edema and conditions that mimic ARDS. In our experience only 10 to 15% may require rigorous investigations, although this proportion may be institution-dependent.