Lung Physiology 5: respiratory failure

Question 1

what is respiratory failure?

Answer 1

inadequate gas exchange by respiratory system meaning blood gases cannot be maintained at a good level (must have low PaO2, may or may not have rise in PaCO2)

Question 2

Describe the 2 types of respiratory failure?

Answer 2

Type 1 respiratory failure:
respiratory system cannot adequately provide oxygen to the body, leading to hypoxemia. (Low PaO2, low/normal PaCO2)
Type 2 respiratory failure:
respiratory system cannot sufficiently remove carbon dioxide from the body, leading to hypercapnia.
(Low PaO2, high PaCO2)

Question 3

hypoxaemia vs hypoxia

Answer 3

Hypoxaemia; a decrease in the partial pressure of oxygen in the blood

Hypoxia; a reduced level of tissue oxygenation

Question 4

Type 1 respiratory failure mechanism:
causes,

Answer 4

Most pulmonary and cardiac causes produce type I failure

Mismatching of ventilation and perfusion e.g. Pulmonary embolism
low ambient oxygen
Shunting
Diffusion impairment e.g. in pneumonia
Alveolar hypoventilation due to reduced respiratory muscle activity, e.g. in acute neuromuscular disease

MANY individual causes, including, infection, congenital, neoplasm, airway, vascular, parenchyma (lung tissue)

Question 5

Type 2 respiratory failure mechanism:
typical causes

Answer 5

Due to inadequate alveolar ventilation:

Increased resistance e.g. copd
Reduced breathing effort (drug effects, brain stem lesion, extreme obesity)
A decrease in the area of the lung available for gas exchange (such as in chronic bronchitis)
Neuromuscular problems

MANY individual causes, including airway, drugs, metabolic, neurological, muscle, polyneuropathy, primary muscle disorders

Question 6

what is cyanosis? clinical symptoms, feature of hypoxic anaemic

Answer 6

a bluish-purple color of the skin- easiest seen under the tongue

if hypoxic anaemic- may not be able to see blue, not enough haemoglobin to see blue tinge

Central Cyanosis
Oral cavity
May not be obvious in anaemic patients
Irritability
Reduced intellectual function
Reduced consciousness

Question 7

Clinical features of hypercapnia

Answer 7

Irritability
Headache
Papilloedema
Warm skin
Bounding pulse

Leading to:
Confusion
Somnolence
Coma

Question 8

Why must you be careful when giving someone with COPD oxygen? What level should their SpO2 be?

Answer 8

chronic hypercapnic patients e.g. COPD lose CO2 drive, chemoreceptors are thought to reset, rely on hypoxic drive to breath instead so by giving them too much O2 they may lose their hypoxic drive to breathe (aim for SpO2 to 88-92%)