2. • Respiratory failure occurs when gas exchange
is inadequate, resulting in hypoxia.
• Def:- Respiratory failure is when the PaO2 < 8k
Pa
• It is subdivided into 2 types according to
PaCO2 level.
3. Type 1 Respiratory Failure
• Is defined as hypoxia (PaO2<8kPa) with a
normal or low PaCO2.
• It is caused primarily by ventilation/perfusion
(V/Q) mismatch eg
• Pneumonia Emphysema
• Pulmonary Odema ARDS
• PE Fibrosing alveolitis
• Asthma
4. Type 2 Respiratory Failure
• Def as hypoxia (PaO2<8k Pa) with hypercapnia
(PaCO2>6k Pa).
• This is caused by alveolar hypoventilation, with or
without V/Q mismatch. Causes include:
1: Pulmonary disease: asthma, COPD, pneumonia,
pulmonary fibrosis, obstructive sleep apnoea
2: Reduced respiratory drive: sedative drugs, CNS tumor
or trauma.
3: Neuromuscular disease: Cervical cord lesion,
diaphragmatic paralysis, poliomyelitis, myasthenia gravis,
Guillian-Barre’ syndrome.
4: Thoracic wall disease: flail chest, kyphoscoliosis.
5. Clinical Features
• C/F are those of the underlying cause together
with symptoms and signs of hypoxia with or
without hypercapnia.
• Hypoxia: Dyspnoea, restlessness, agitation,
confused, central cyanosis. If longstanding
hypoxia: polycythaemia; pulmonary
hypertension; cor pulmonary.
• Hypercapnia: Headach, peripheral vasodilation;
tachycardia; bounding pulse, tremor/flap;
papilloedema; confusion; drowsiness; coma.
6. Investigations
• These are aimed at determining the
underlying cause:
• Blood test: FBC, U&E, CRP, ABG.
• Radiology: Chest Xray
• Microbiology: sputum and blood cultures (if
febrile)
• Spirometry (COPD, neuromuscular disease,
Guillain-Barre’ syndrome)
7. Management
• Management depends on the cause:
• Type 1 Respiratory Failure:
• Treat underlying cause.
• Give O2 (35%-60%) by facemask to correct
hypoxia
• Assisted ventilation if PaO2<8k Pa despite60%
O2.
8. Type II Respiratory Failure
• The respiratory center may be relatively insensitive to CO2
and respiratory could be driven by hypoxia.
• Treat the underlying cause.
• Controlled O2 therapy: start at 24%O2. Oxygen therapy
should be given with care. Nevertheless, don’t leave
hypoxia untreated.
• Recheck ABG after20mins. If PaCO2 is steady or increase O2
concentration to 28%. If PaCO2 has risen >15k Pa and the
patient is still hypoxia, consider a respiratory stimulant (eg
doxapram 15-4mg/min IVI) or assisted ventilation (eg Non-
invasive positive pr ventilation).
• If this fails, consider intubation and ventilation, if
appropriate.
