Pulse Oximetry

Question 1

Pulse oximetry - what does it measure

Answer 1

> arterial oxygen saturation (oxygen bound to Haemoglobin)
Sats usually correlates to arterial oxygenation
As saturated and unsaturated haemoglobin absorb different amounts of light

Question 2

Pulse Oximetry - Method + Normal Values

Answer 2

> Light = passed from source through body part (finger, toe, ear, nose) to photodetector
Normal oxygen sats = ~95%
adequate = 92%
<90% is hypoxaemia (chronic diseases may have lower ranges)

Question 3

Pulse oximetry - benefits and use

Answer 3

> Benefits

• cheap + easy to perform
• non-invasive
• instant feedback

> Use

• assessment tool (pre/during treatment)
• Outcome measure (post treatment)

Question 4

Pulse oximetry - method is affected by

Answer 4

> movement (tremor)
> nicotine stains 
> nail polish 
> bruising 
> clubbing

Question 5

Pulse oximetry - test = compromised by:

Answer 5

> cold peripheries or hyothermia 
> low blood pressure 
> peripheral vascular disease
> anaemia 
*ie anything that would mean less blood in the area or less haemoglobin in blood

Question 6

Arterial Blood Gases - method

Answer 6

> Diagnostic test on blood taken from artery
Catheter or arterial stab (radial, brachial, femoral)
Invasive + Complex
Complications
- arteriospasm (constriction of artery to heal - cuts off blood supply)
- haematoma (bleeding)
- nerve damage
- fainting/vasovagal response (drop in bp)
- infection risk

Question 7

Arterial Blood gases - Results

Answer 7

> pH - related to hydrogen levels should be (~7.4)
partial pressure of Co2
Partial pressure of O2
amount of bicarbonate ions
base excess (gives us an idea of source of acidosis/alkalosis - respiratory or metabolic)

• Acidosis = low pH (too much Co2 or little bicarbonate)
• Alkalosis = high pH (too little Co2 or much bicarbonate)
• Compensation = returning pH to normal