Spurious hypoxaemia in a patient with leukaemia and extreme leucocytosis.

Rapid consumption of oxygen by leucocytes can result in erroneous diagnosis of severe hypoxaemia in patients with extreme leucocytosis. We report a case of chronic myeloid leukaemia, extreme leucocytosis and arterial hypoxaemia which was out of proportion to the clinical and radiological evidence of lung disease. The pseudohypoxaemia was confirmed by pulse oximeter and became less significant after successful reduction of leucocyte counts following leucophoresis and chemotherapy. Serial arterial blood gas analysis also demonstrated a slower initial rate of decay of PaO2 as the leucocyte count decreased with treatment.