Oxygen and Respiratory Failure (Respiratory)

Question 1

What is type 1 and 2 respiratory failure?

Answer 1

Type 1: short of oxygen. Type 2: short of oxygen and too much CO2.

Question 2

Are there specific diseases associated with type 1 or 2 respiratory failure?

Answer 2

No, there are no diseases that are always associated with just one type.

Question 3

How does giving controlled oxygen let us find out about damage to the lungs?

Answer 3

The saturation curve becomes useful as the saturation will fall a lot more so will be more easily detectable.

Question 4

What should people’s oxygen saturation not be over if they are on oxygen?

Answer 4

98%.

Question 5

What can happen if you give someone with type 2 respiratory failure oxygen?

Answer 5

It can increase their pCO2 which can cause severe acidosis.

Question 6

What 4 things can cause patients to retain CO2?

Answer 6

V/Q mismatch (most important), the Bohr effect, the haldane effect and hypoxic drive.

Question 7

How can V/Q mismatch cause CO2 retention?

Answer 7

Giving excess oxygen causes vasoconstriction to reverse, perfusion becomes good but ventilation is poor.

Question 8

How can the Bohr effect cause CO2 retention?

Answer 8

People with type II resp failure often have low SaO2 as oxygen dissociates more easily from Hb due to more pCO2.

Question 9

How does the Haldane effect cause CO2 retention?

Answer 9

Chronically hypoxaemic patient has low Hb sats, Co2 occupies empty binding sites on Hb, giving lots of oxygen pushes CO2 off Hb into the system.

Question 10

What is hypoxic drive?

Answer 10

Normal respiration is driven by CO2 chemoreceptors, chronic hypercarbia leads to desensitation of these receptors, oxygen chemoreceptors then become the primary drive for respiration.

Question 11

What does hypoxaemia cause in the body?

Answer 11

Altered mental state, cyanosis, dyspneoa, tachypnoea, arrhythmias.

Question 12

In hypoxia name the PO2 where hyperventilation, loss of consciousness and then death occur?

Answer 12

Hyperventilation: 5.3kPa. Loss of consciousness: 4.3kPa. Death: 2.7kPa.

Question 13

What do the surviving sepsis and critical care consensus guidelines say the target SaO2 should be?

Answer 13

Surviving sepsis: 85-95%. Critical care consensus: >90%.

Question 14

What are the causes of hypoxia?

Answer 14

Circulatory hypoxia, anaemic hypoxia, toxic hypoxia, hypoxic hypoxaemia (due to lungs?).

Question 15

What is circulatory hypoxia?

Answer 15

Where oxygenated blood cannot get to the tissues (global or local reduction).

Question 16

What can cause toxic hypoxia?

Answer 16

Cyanide, arsenic, carbon monoxide and alcohol.

Question 17

What are the many causes of hypoxic hypoxaemia?

Answer 17

Low FiO2 (e.g. altitude), alveolar hypoventilation (opiates, glotic swellings, severe scoliosis, obesity, ondine’s curse), impaired diffusion (failure of alveolar-endothelial interface), shunt (perfusion without ventilation), dead space (ventilation without perfusion), ventilation perfusion mismatch.

Question 18

What is oxygen not a treatment for?

Answer 18

Breathlessness, it should only be used to treat hypoxaemia.

Question 19

When should you give as much oxygen as possible?

Answer 19

Cardiac arrest, polytrauma, severe sepsis, anaphylaxis.

Question 20

What are the target saturations for people at risk of chronic type 2 resp failure and everyone else?

Answer 20

88-92% and 94-98% respectively.

Question 21

What may cause problems when using non-rebreathing masks?

Answer 21

A high tidal volume.