Oxygen

Question 1

SaO2

Answer 1

Saturation of arterial blood

Question 2

SpO2

Answer 2

Saturation measured using a pulse oximeter

Question 3

PaO2

Answer 3

The amount of oxygen dissolved in arterial blood plasma

Question 4

What will happen to the amount of oxygen bound to haemoglobin if the partial pressure of oxygen increases?

Answer 4

Increase - but not proportionally

Question 5

FiO2

Answer 5

The fraction of inspired oxygen

Question 6

Why do patients retain CO2?

Answer 6

• V/Q mismatch

- The haldane effect

Question 7

Causes of hypoxic hypoxaemia

Answer 7

Low inspired O2 conc.
Alveolar hypoventilation
Impaired diffusion

Question 8

Shunting

Answer 8

Good perfusion, bad ventilation

Question 9

Dead space

Answer 9

Good ventilation, bad perfusion

Question 10

When does shunting occur?

Answer 10

COPD, pulmonary oedema, sarcoidosis, lung cancer etc.

Question 11

When does dead space occur?

Answer 11

Pulmonary embolism, pulmonary vasculitis, pulmonary hypertension

Question 12

Nasal canula

Answer 12

Well tolerated, low flow - uncontrolled FiO2

Question 13

Hudson face mask

Answer 13

Cheap and simple, but can’t cope with high flow

Question 14

Venturi mask

Answer 14

Fixed performance - good for type 2 res. failure

Question 15

Resivoir mask

Answer 15

Non-rebreather, used in emergencies

Question 16

Flow rate for nasal cannula

Answer 16

2-4 l/min

Question 17

Flow rate for hudson mask

Answer 17

4-8 l/min

Question 18

Flow rate for non-rebreather mask

Answer 18

15 l/min