Resp failure

Question 1

Oxygen delivery of:
high flow nasal 
Double jet 
trauma mask 
hudson 
nasal prongs

Answer 1

high flow nasal 90%
Double jet  60-80%
trauma mask 60-70%
hudson 40-60%
nasal prongs 30-40%

Question 2

4 main mechanisms of resp failure

Answer 2

Alveolar hypoventilation
Diffusion deficit
Shunt
Ventilation – perfusion mismatch

Question 3

2 mechanisms of hypoventilation ?

Main type of resp failure in hypoventilation

Answer 3

1. A reduction in minute ventilation.
2. An increase in the proportion of dead space ventilation which can either be anatomical or
   physiological.

Type 2 - CO2 retention

Question 4

What is the alveolar gas equation

Answer 4

Patrial pressure of OXYGEN in alveolar air = partial pressure of oxygen in inspired air - (partial pressure of CO2 in alveolus / R)

PAO2 = PIO2 - PACO2 / R

PAO2 is the partial pressure of oxygen in alveolar air.
PIO2 is the partial pressure of oxygen in inspired air.
PACO2 is the partial pressure of CO2 in alveolar air.
R is the respiratory quotient

Question 5

Pathophysiology of diffusion deficit?
What makes up the normal diffusion barrier?
Most common acute/chronic cause of diffusion deficit?

Answer 5

affecting the barrier which is normally present between alveolar gas and the capillary blood

alveolar epithelial cell, the interstitial space and a
capillary endothelial cell

Pulm oedema/plum fibrosis

Question 6

2 Types of shunt

Answer 6

bypassing the lungs
completely (extra-pulmonary shunt) - cardiac usually

bypassing through the lungs without adequate oxygenation (intra-pulmonary shunt)

Question 7

The 2 most common causes of intrapulmonary shunting

Answer 7

alveolar filling (with pus, oedema, blood or tumour)

atelectasis

Question 8

A most common mechanism of hypoxia and what is it

Answer 8

ventilation-perfusion mismatch

degree of shunt and a degree of dead space in the same lung.

Question 9

CIs to NIV / CPAP - name 4

Answer 9

Decreases consciousness 
facial trauma 
unprotected airways 
vomiting 
poor compliance 
Recent upper GI surgery / high gastric anastomoses

Question 10

CPAP best for?

Usual pressures

Answer 10

cardiogenic pulmonary oedema and can allow time for medical therapy to work. It may also help in
ARDS.

5 and 10 cm of H2O

Question 11

Why not NIV in pneumonia

Answer 11

unlikely to resolve quickly ->use invasive ventilation

Question 12

Indications for respiratory support

Answer 12

hypoxia, hypercarbia, increased WOB, reduced consciousness, exhaustion