Lecture 2

Question 1

What causes hypoxaemic RF?

Answer 1

1. Inadequate O2 TRANSFER into the blood
   - reduced fresh air
   - reduced surface area for gas exchange
   - diffusion impairment
2. Inadequate O2 TRANSPORT
   - Hb
   - circulation impairment
3. Extraction/utilisation impairment

Question 2

How can you improve PaO2?

Answer 2

1. Improve diffusion
   - O2 therapy - increases FiO2, PatmosO2
2. Increase SA for gas exchange
   - CPAP/PEEP - prevents the alveoli from fully closing

Question 3

Examples of controlled O2 devices

Answer 3

Venturi

Mechanical ventilator

Question 4

Examples of uncontrolled O2 devices

Answer 4

Simple face mask
High concentration mask
Tracheostomy mask
Nasal catheter/high flow humidified

Question 5

What are the dangers of O2 therapy

Answer 5

1. Absorption atelectasis (when the O2 gets used up - no nitrogen - so the airway collpases)
2. FIre
3. Toxicity if FiO2 > 0.7 for >1-2 days
4. Reduced matching of blood+gas d/t hypoxia induced vasodilation

Question 6

To prevent complications from O2 therapy, keep FiO2 < ?

Answer 6

0.6

Question 7

The alveolar gas equation - describe the important components and if you remember it - say it

Answer 7

P(alv)O2 = Pb - PalvH2O)*FiO2 - PaCO2/RQ

• FiO2 affects how much O2 makes it into our blood
• higher the PaCO2 - lower the PAO2

Question 8

What is the effect of PEEP on alveoli?

Answer 8

postive airway pressure = reduced alveolar emptying = increased FRC= increased SA for gas exchange

also RE-EXPANDS collapsed alveoli

Question 9

What are the benefits of high flow nasal canula (HFNC)?

Answer 9

• combines O2 therapy + humidification + low levels CPAP

Question 10

CPAP vs PEEP

Answer 10

CPAP:

• used with spontaneous breaths
• continuous +ve airway pressure (i.e on inspiration + expiration)

PEEP:

• used with ventilator breaths
• +ve pressure at the mouth at the end of expiration