Respiratory failure
31/08/2011
Vivian Ho
Contents
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Definition
Types
Pathogenesis
Effects
Blood gases
Management
Definition
• Failure to maintain gas exchange
• Numbers…
 pO2 < 60 mmHg
 pCO2 > 50mmHg
Types
• Acute / acute on chronic / chronic
• Type 1 vs Type 2
• Causes
Pathogenesis
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Hypoventilation
V/Q inequality
Shunt
Diffusion impairment
Pathogenesis
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Hypoventilation
V/Q inequality
Shunt
Diffusion impairment
Pathogenesis
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•
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Hypoventilation
V/Q inequality
Shunt
Diffusion impairment
Pathogenesis
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Hypoventilation
V/Q inequality
Shunt
Diffusion impairment
PaO2
40
0.25
0.75 Time (s)
Effects
Blood gases 1
pH
pCO2
pO2
Na
K
HCO3
BE
FiO2
7.47
33
47
144
3.7
24
0.5
55%
Blood gases 2
pH
pCO2
pO2
Na
K
HCO3
BE
FiO2
7.19
74
59
132
4.7
28
-1.6
35%
Blood gases 3
pH
pCO2
pO2
Na
K
HCO3
BE
FiO2
7.46
30
58
136
4.8
21
-2
85%
Management
• Treat cause
• Oxygen
• Ventilatory support
To tube or not to tube
Ventilatory support
NIV
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What is it?
How does it work?
When does it work?
What does the evidence suggest?
NIV
• Indications
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Hypercapnic respiratory failure
COPD with resp acidosis pH 7.25-7.35
Cardiogenic pulmonary oedema
Pneumonia in the immunosuppressed
Weaning from the ventilator in hypercapnic
COPD patients
NIV
• Contraindications
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Airway
Facial abn
Respiratory Arrest
Severe hypoxaemia
Untreated pneumothorax
Haemodynamic instability
Agitation
GI bleed / ileus/ surg
Cochrane
• NIV vs Medical therapy alone
– Lower mortality
NNT 8
– Prevent intubation
NNT 5
– Length of stay
– Improved pH/paCO2/RR within 1h of tx
NIV
• Compared with intubation..
– Hosp acq pneumonia
– Complications
Mechanical Ventilation
• Indications for intubation
– Airway
– Ventilation
– Improve Oxygenation
– Decrease work of breathing
– Stabilise chest wall in severe injury
Summary
• Resp failure is the inability to maintain
adequate gas exchange
• Type 1: hypoxaemic
• Type 2: hypercapnic + hypoxaemic
• NIV should be considered in
– patients with hypercapnic resp failure
– cardiogenic pulmonary oedema
– pneumonia in immunosuppressed