Chest X-ray shows B/L lung infiltrates next investigation is

In ARDS, a chest radiograph will show bilateral lung infiltrates. Chest CT scanning in ARDS reveals extensive heterogeneity of lung involvement. Chest X-ray in ARDS usually reveals opacities consistent with the pulmonary edema and often involves three-quaers of lung fields. But chest X-ray in ARDS does demonstrate pleural effusion, cardiomegaly, and pulmonary vascular distribution as seen in pure cardiogenic pulmonary edema. Reference: Harrison's Medicine, 20TH edition, page no:2032