Pseudohypoxaemia in a patient with acute leukaemia.

Patients with acute leukaemia may have spuriously low arterial oxygen tensions (PaO2). The markedly increased numbers of white blood cells in these patients rapidly consume dissolved plasma oxygen resulting in dramatically decreased PaO2 and calculated oxygen saturations. The case history is reported of a patient with a white blood count of 191 000/mm3 in whom multiple arterial blood gas measurements documented hypoxaemia out of proportion to the clinical picture. Pulse oximetry was used to confirm higher haemoglobin oxygen saturations and to establish the spuriously low plasma oxygen tensions in this patient.