ICU SAQs · Oxygen & gas exchange
The four mechanisms of hypoxaemia and the A-a gradient
A CICM Second-Part SAQ testing the four mechanisms (hypoventilation, diffusion, V/Q mismatch, shunt), the A-a gradient separation, and the oxygen-response test (shunt does not correct).
On this page
Study tools
Target exams
CICMFFICMEDIC
Prompt
A patient has a PaO2 of 55 mmHg on room air. Outline how you would use the mechanisms of hypoxaemia and the A-a gradient to localise the cause, and how each mechanism responds to supplemental oxygen.
Question
A patient has a PaO2 of 55 mmHg on room air. Outline how you would use the mechanisms of hypoxaemia and the A-a gradient to localise the cause, and how each mechanism responds to supplemental oxygen.
References4ShowHide
- [1]Frat JP, Thille AW, Mercat A, et al. High-flow oxygen through nasal cannula in acute hypoxemic respiratory failure (FLORALI). New England Journal of Medicine, 2015.PMID 25981908
- [2]Chu DK, Kim LH, Young PJ, et al. Mortality and morbidity in acutely ill adults treated with liberal versus conservative oxygen therapy. Lancet, 2018.PMID 29726345
- [3]Bersten AD, Soni N (eds) Oh's Intensive Care Manual. 8th edition, Elsevier, 2018.
- [4]Marino PL The ICU Book. 4th edition, Lippincott Williams & Wilkins, 2014.