Do changes in pulse oximeter oxygen saturation predict equivalent changes in arterial oxygen saturation?
BACKGROUND
This study investigates the relation between changes in pulse oximeter oxygen saturation (SpO2) and changes in arterial oxygen saturation (SaO2) in the critically ill, and the effects of acidosis and anaemia on precision of using pulse oximetry to predict SaO2.


METHODS
Forty-one consecutive patients were recruited from a nine-bed general intensive care unit into a 2-month study. Patients with significant jaundice (bilirubin >40 micromol/l) or inadequate pulse oximetry tracing were excluded.


RESULTS
A total of 1085 paired readings demonstrated only moderate correlation (r= 0.606; P < 0.01) between changes in SpO2 and those in SaO2, and the pulse oximeter tended to overestimate actual changes in SaO2. Anaemia increased the degree of positive bias whereas acidosis reduced it. However, the magnitude of these changes was small.


CONCLUSIONS
Changes in SpO2 do not reliably predict equivalent changes in SaO2 in the critically ill. Neither anaemia nor acidosis alters the relation between SpO2 and SaO2 to any clinically important extent.
Perkins
Gavin D
GD
Intensive Care Unit, Birmingham Heartlands and Solihull NHS Trust (Teaching), Birmingham Heartlands Hospital, Birmingham, UK.
McAuley
Daniel F
DF
Giles
Simon
S
Routledge
Helen
H
Gao
Fang
F
D000138:Acidosis; D000368:Aged; D000369:Aged, 80 and over; D000740:Anemia / Q000503:physiopathology*; D001158:Arteries; D016638:Critical Illness; D005260:Female; D006801:Humans; D007362:Intensive Care Units; D008297:Male; D008875:Middle Aged; D010092:Oximetry; D010100:Oxygen / Q000097:blood*; D010101:Oxygen Consumption / Q000502:physiology*; D006113:United Kingdom
D010100:Oxygen