Oxygen and Respiratory Failure

Question 1

Type 1 Respiratory Failure

Answer 1

Short of oxygen

Question 2

Type 2 Respiratory Failure

Answer 2

Short of oxygen and too much carbon dioxide

Question 3

What happens when pO2 rises?

Answer 3

pCO2 also rises, causing acidosis which can be very severe

Question 4

The effect of pCO2 on Hb

Answer 4

Haldane effect- O2 can displace CO2 from Hb

Bohr effect- high conc of CO2 prevent O2 binding to Hb

Question 5

What drives normal respiration?

Answer 5

CO2 chemoreceptors

Question 6

What causes desensitisation of CO2 receptors?

Answer 6

Chronic hypercarbia

Question 7

Symptoms of severe hypoxaemia

Answer 7

altered mental state, cyanosis, dyspnoea, tachypnoea, arrhythmias, hyperventilation (in some cases)

Question 8

Toxic hypoxia

Answer 8

Cyanide inhibits ATP at a cellular level, shifting cells from aerobic to anaerobic respiration, meaning cells no longer take up oxygen

Indistinguishable from CO poisoning clinically

Question 9

Antidote for toxic hypoxia

Answer 9

Nitrates eg Amyl Nitrite

but this can cause dangerously high levels of methaemoglobin

Question 10

Shunting

Answer 10

Perfusion without ventilation

Question 11

Dead space

Answer 11

ventilation without perfusion

Question 12

V/Q mismatch at lung apex

Answer 12

Good V, poor Q

Question 13

V/Q mismatch at lung base

Answer 13

Good Q, poor V

Question 14

Treatment for hypoxaemia

Answer 14

Oxygen, although it can do harm

Question 15

Nasal cannulae

Answer 15

Well tolerated
Low flow only
Uncontrolled FiO2
Dependent on nasal breathing

Question 16

Variable Performance Mask

Answer 16

Cheap and simple
5-15l/min
Uncontrollable FiO2
Unable to cope with high flow requirements

Question 17

Venturi mask

Answer 17

Fixed performance

Flow of up to 250l/min

Question 18

Non-rebreathing mask

Answer 18

Up to 85% FiO2, uncontrolled
flow limited to output of wall
be aware of large VT