Pulse Oximetry

Question 1

What is Pulse oximetry?

Answer 1

Non-invasice measurement of estimated saturation of the arterial haemoglobin with oxygen

Question 2

How does PO work?

Answer 2

A sensor with the light of 2 different wavelengths (650nm and 805nm) is passed through the patient to a photo detector. The light is parted by haemoglobin by amounts which differe depending on whether it is saturated or desaturated with oxygen. Hameoglobin fully saturated = appear darker

calculating the absorption at the two wavelengths the processor can compute the proportion of haemoglobin which is oxygenated

Also displays pulse rate

Question 3

Where is a PO placed

Answer 3

thin part of the body

fingers, toes, ears or feet

Question 4

Normal values of SPO2

Answer 4

95% above

Question 5

when does the oxyhaemoglobin dissociation curve become sttep?

Answer 5

below 90%
Reflects the rapid desaturation that occurs with diminishing oxygen partial pressure (PaO2)

most machine = alarm 90%

Question 6

Issues with PO

Answer 6

Reading tells how full the Hb is but if low Hb total O2 may be inadequate

bbody temp
poor peripheral circulation
nail polish
some drug groups cause peripheral vasoconstriction

Question 7

SpO2 should be recorded with

Answer 7

level of respiratory support - type and inspired O2 concentration