8-4
8.5 Measurement Limitations
If you doubt the measured SpO
2
, check patient vital signs first. Then check the patient
ventilator and SpO
2
sensor. The following factors may influence the accuracy of
measurement:
Ambient light
Physical movement (patient and imposed motion)
Diagnostic testing
Low perfusion
Electromagnetic interference, such as MRI environment
Electrosurgical units
Dysfunctional haemoglobin, such as carboxyhemoglobin (COHb) and methemoglobin
(MetHb)
Presence of certain dyes, such as methylene and indigo carmine
Inappropriate positioning of the SpO
2
sensor, or use of incorrect SpO
2
sensor
Drop of arterial blood flow to immeasurable level caused by shock, anemia, low
temperature or vasoconstrictor.