A 7-month-old girl presented to the emergency department with a 12-hour history of difficult breathing. The girl was alert but with a severe tachy-dyspnoea, chest retractions and nodding. Vital signs showed: respiratory rate 70/min, pulse rate 150/min and oxygen saturation 92% on room air. At chest auscultation, mild bilateral basal crackles were noted. Repeated albuterol inhalations, systemic steroid and oxygen administration through high flow nasal cannula were administered, but respiratory distress worsened in the next 2 hours. Capillary blood gas analysis showed: pH 7.37 pCO2 27 mm Hg, HCO3 17 mm Hg. A chest radiograph was performed (figure 1).

Chest X-ray shows enlargement of the cardiac silhouette with abnormal lung fields characterised by alveolar oedema, air bronchogram on the right side and left basal pleural effusion.

Which is the most likely diagnosis in this patient?

Bronchiolitis

Acute respiratory distress syndrome

Acute heart failure secondary to dilated cardiomyopathy

Diabetic ketoacidosis

Which test may help to …