Question normal

A 39-year old man with history of ‘asthma’ presents to emergency department at night with symptoms of difficulty breathing as if not getting enough air and feeling light-headed. He denied symptoms of chest pain, tightness or heaviness but described vague abdominal discomfort. Physical examination was unremarkable, lungs were clear and had mild abdominal tenderness without rebound.

Laboratory data shows normal hemoglobin of 140 g/L, platelets of 358, slightly high white blood cell count of 11.7, serum glucose of 4.3 mmol/L, serum sodium of 135 mmol/L, chloride of 97 mmol/L, serum potassium of 4.5 mmol/L, BUN of 6.9 mmol/L, creatinine of 100 umol/L, normal CK of 65. An ECG was normal. A Chest X-ray showed plate-like right lower lobe atelectasis. An arterial blood gas showed a pH of 7.38, pCO2 of 18, pO2 of 90, bicarbonate 11 mmol/L and SaO2 of 97% on room air.

What is your diagnosis?