Case 1

A 37-year-old Afro-Caribbean female of moderate build (approximate weight of 70kg) attends the ED complaining of a 2-hour period of SOB. She is married with two children and on the OCP and smokes 10 cigarettes per day. There is nothing else of note on enquiry except that she had a mild faint spell before the SOB started and her periods are heavier than normal. Her family history is unremarkable and she works as an office cleaner and hasn't been on holiday abroad for more than a year.

On examination she is anxious but able to speak fluently and observations on room air reveal the following:

• RR = 22/min
• HR = 98/min
• BP = 108/68
• SaO2 = 92%
• T = 37.3^oC

Her chest seems clear on auscultation and her heart sounds are normal with no murmurs. The rest of the physical examination is unrevealing. You decide to put her on oxygen with a 24% Venturi mask, which picks her oxygen saturation up to 96% and you undertake an ABG. The image shows the ABG results. Click on the image to enlarge.

What is the amount of oxygen being transported in her blood?

Employing the alveolar gas equation, what is the A-a gradient?

From the previous answer, how would you classify this patient?

Which of the following is the likely diagnosis in this patient?