Sats

Question 1

What a pulse oximeter does

Answer 1

Measures Hb saturation level with O
DeO Hb absorbs RED
Oxy Hb absorbs INFRARED
Only detects pulsatile arterial blood
NOT work out amount of Hb present eg anaemia
Can estimate pO2 from dissociation curve

Question 2

Advantages

Answer 2

Easy
Portable
Non invasive
Cheap
Continuous
Good for monitoring acutely ill or at risk of deterioration

Question 3

Normal

Answer 3

94-98%

Question 4

Interfering factors that give falsely low reading

Answer 4

Movement artefact
Peripheral vascular disease
Hypothermia
Nail varnish

Question 5

Falsely high cause

Answer 5

Dark skin pigmentation
Raised bilirubin
Carboxyhaemoglobin (CO poisoning)- cant tell difference so total saturation of CO and O is read. Need to do ABG. Dont use for smoke inhalation, heavy smoking or known CO poisoning.

Question 6

Disadvantages

Answer 6

Various influencing factors
Not tell you pH or pCO2
Less accurate under 75%

Question 7

ABG indications

Answer 7

Unexpected deterioration in an ill patient.
Acute exacerbation of chronic chest condition.
Impaired conciousness or respiratory effort.
Signs of CO2 retention eg bounding pulse, drowsy, flapping tremor, headache.
Cyanosis, confusion, visual hallucinations.
To validate pulse ox measurement.

Question 8

COPD

Answer 8

Target 88-92%
Respiratory drive- LT hypercapnia= central chemoRs no longer stimulated by it= hypoxia is main respiratory driver, so too much O therapy can= respiratory depression.

Question 9

COPD

Answer 9

Target 88-92%
Respiratory drive- LT hypercapnia (warm hands, asterixis)= CSF acidity corrected by choroid plexus, central chemoRs no longer stimulated by high CO2= peripheral chemoR sensing hypoxia is main respiratory driver, so too much O therapy can= respiratory depression AND reduced hypoxic vasoconstriction in poorly ventilated alveoli so worse V/Q mismatch.
Use titrated O with monitoring.

Question 10

Alternative sites

Answer 10

Ear lobe
Other finger, other hand
Toes

Question 11

Femoral artery

Answer 11

Continuation of external iliac after cross under inguinal ligament.
Mid point bewteen pubis symphisis and ASIS.
Superficial in femoral triangle.

Question 12

Radial artery

Answer 12

Medial to brachioradalis.