Respiratory failure

Question 1

Definition

Answer 1

–syndrome in which the respiratory system fails in one or both of its gas exchange functions: oxygenation and carbon dioxide elimination.

–In practice, it may be classified as either hypoxemic (type 1) or hypercapnic (type 2)

Question 2

Type 1 respiratory failure causes:

Answer 2

defined as hypoxia (PaCO2 <8kPa) with a normal or low PaCO2. It is caused primarily by ventilation/perfusion

• pneumonia
• pulmonary oedema
• PE
• Asthma
• emphysema
• Pulmonary fibrosis
• ARDS

Question 3

Type 2 respiratory failure causes

Answer 3

defined as hypoxia (PaO2 <8pKa) with hypercapnia (paCO2 >6.0kPa). This is caused by alveolar hypoventilation, with or witout v/q mismatch

• pulmonary disase - asthma, COPD, end-stage pulmonary fibrosis
• reduced respiratory drive - sedative drugs, CNS tumour
• Neuomuscular disease: cervical cord lesion, Myasthenia gravis
• thoracic wall disease: kyphoscoliosis

Question 4

Clinical features

Answer 4

Hypoxia: Dypsnoea, restlessness, agitation, confusion, central cyaonosis

Hypercapnia: headache, peripheral vasodilation, tachycardia, bounding pulse

Question 5

Investigations `

Answer 5

Aimed at determining the underlyin cause:

• FBC
• ABG
• CXR
• Microbiology- sputum and blood cultures
• Spirometry

Question 6

type 1 - management

Answer 6

• treat underlying cause
• Give Oxygen (35-60%) by facemask
• assisted venilaition if PaO2 <8kPa despite 60% O2

Question 7

Type 2 management

Answer 7

• treat underlying cause
• controlled oxygen therapy- start at 24%
• recheck ABG after 20 min. If PaCO2 is steady or slow, increase O2 concentration to 28%. If PaCO2 has risen >1.5pKa and the patient is still hypoxic consider assisted ventilation