Oxygen Delivery

Question 1

What does shunt mean?

Answer 1

Alveoli perfused but not ventilated e.g. pneumonia

Question 2

What is dead space?

Answer 2

Alveoli ventilated but not perfused e.g. PE

Question 3

What is the effect of positive airway pressure?

Answer 3

Outside lungs > inside lungs

• so air moves down the pressure gradient
• -> less respiratory effort and reduced work of breathing

Question 4

What is recruitment?

Answer 4

At the end of expiration, small bronchioles/alveoli collapse (normal)

Question 5

What is PEEP and what effect does it have?

Answer 5

Positive end expiratory pressure

• helps keep small airways open if elderly/lung disease
• -> increased gas exchange + reduced physiological shunt

Question 6

Which masks are used for simple oxygen delivery?

Answer 6

Nasal cannula
Simple (Hudson) face mask
Venturi face mask
Non-rebreather mask

Question 7

What is the flow of oxygen through a nasal cannula?

Answer 7

2-4 l/min

24-35% FiO2

Question 8

What is the flow of oxygen through a simple face mask?

Answer 8

5-10 l/min

35-60% FiO2

Question 9

What is a Venturi face mask and how is it better than a simple face mask?

Answer 9

Simple face mask with Venturi device on the end

- fixed performance device –> know exactly how much oxygen you are giving (good for COPD)

Question 10

What is the flow of oxygen through a venturi mask?

Answer 10

Depends on which device chosen:

• 24%, 28%, 35%, 40% or 60% FiO2
• tells you on the device which flow is needed

Question 11

What is a non-rebreather mask and what is the flow of oxygen?

Answer 11

Mask with a one way valve + reservoir bag

- 15 l/min, 80-98%

Question 12

What is a bag-valve mask?

Answer 12

In crash trolley, used to give assisted breathes

Question 13

When might oxygen delivery with respiratory support be required?

Answer 13

When patient still hypoxic despite maximum simple oxygen delivery

Question 14

What are the options for the delivery of oxygen with respiratory support?

Answer 14

CPAP, BiPAP or HFNO

Question 15

What are the indications for O2 delivery with respiratory support?

Answer 15

Requiring FiO2 >/= 60%
Type 2 respiratory failure on ABG
Evidence of respiratory distress

Question 16

What is HFNO?

Answer 16

High flow nasal oxygen

- wide bore nasal cannula attached to air-oxygen mixer

Question 17

What is delivered with HFNO?

Answer 17

Up to 70 l/min oxygen

Up to 3cmH2O of PEEP (although not a reliable amount)

Question 18

What is CPAP and how is it delivered?

Answer 18

Continuous positive airway pressure

- hood or tight fitting mask (only works if good seal)

Question 19

What is delivered with CPAP?

Answer 19

High oxygenation

Measurable/titrated PEEP (reduces WOB)

Question 20

Which type of patient is CPAP good for?

Answer 20

Type 1 respiratory failure e.g. pulmonary oedema

Question 21

What is the different between CPAP and BiPAP?

Answer 21

BiPAP provides alternating pressures for inspiration + expiration (higher for expiration –> PEEP)

BiPAP os VENTILATORY support
CPAP is RESPIRATORY support

Question 22

Which type of patient is BiPAP good for?

Answer 22

Type 2 respiratory failure e.g. COPD

Question 23

What are the disadvantages of CPAP/BiPAP?

Answer 23

Claustrophobic
Difficult to tolerate
Can’t eat or drink

Question 24

What is another name for BiPAP?

Answer 24

Non invasive ventilation (NIV)

Question 25

What are the options for delivery of invasive ventilation?

Answer 25

ET tube or tracheostomy

Question 26

What are the risks associated with invasive ventilation?

Answer 26

Ventilation pneumonia
Ventilation lung injury
- volutrauma (volume overload)
- barotrauma (pressure overload)
CV compromise from pressure in lungs e.g. reduced venous return to heart