Respiratory failure

Question 1

what causes type 1 resp failure?

Answer 1

V/Q mismatch and diffusion failure

Question 2

what causes type 2 resp failure?

Answer 2

Alveolar hypoventilation ± V/Q mismatch

Question 3

what are the causes of V/Q mismatch ?

Answer 3

PE, pulmonary hypertension, pulmonary shunt

asthma (early)

pneumothorax

atelectasia

Question 4

state some obstructive causes of alveolar hypoventilation?

Answer 4

COPD
asthma 
bronchiectasis
bronchiolitis 
cancer 
epiglottitis

Question 5

state some restrictive causes of alveolar hypoventilation?

Answer 5

decreased resp drive (CNS sedation, trauma, tumour)

neuromuscular disease (vertical cord lesion, polio, GBS, MG)

chest wall (flail, kyphoscoliosis, obesity)

fluid and fibrosis

Question 6

how do you calculate A-a gradient?

Answer 6

PAO2= (95 x FiO2) – (PaCO2/0.8)

FiO2 = fraction of inspired air (eg. 21% in air)

Question 7

state three features of chronic hypoxia?

Answer 7

􏰁 Polycythaemia
􏰁 PHT
􏰁 cor pulmonale

Question 8

state 5 features of hypercapnoea?

Answer 8

􏰀 Headache
􏰀 Flushing and peripheral vasodilatation 
􏰀 Bounding pulse
􏰀 Flap
􏰀 Confusion → coma

Question 9

what is the treatment for type 1 resp failure?

Answer 9

􏰀 Give O2 to maintain SpO2 94-98%

􏰀 Assisted ventilation if PaO2<8KPa despite 60% O2

Question 10

what is the treatment for type 2 resp failure?

Answer 10

Controlled O2 therapy @ 24% O2 aiming for SpO2 88-92% and a PaO2 >8kPa

Check ABG after 20mins
- If PaCO2 ↑>1.5KPa and pt. still hypoxic, consider
NIV or respiratory stimulant (e.g. doxapram)

Question 11

what is the SpO2 target for r those at risk or hypercapnic resp failure?

Answer 11

88-92%

Question 12

what O2 mask should be used for those at risk of hypercapnic resp failure?

Answer 12

Blue Venturi @ 2-4L/min

Question 13

what volume per min of O2 can nasal canals give?

Answer 13

1-4L/min = 24-40% O2

Question 14

what volume per min of O2 can Non-rebreathing Mask?

Answer 14

60-90% at 10-15L

Question 15

what are Venturi Mask used for?

Answer 15

Provide precise O2 concentration at high flow rates

Question 16

what are the different colours and O2% of the venturi masks?

Answer 16

􏰁 Yellow: 5%
􏰁 White: 8%
􏰁 Blue: 24%
􏰁 Red: 40%
􏰁 Green: 60%