Respiratory Failure

Question 1

What are the 2 types of Resp Failure?

Answer 1

Type 1- hypoxaemia with normocapnia (low O2 nomal CO2)
Type 2 - hypoxemia with hypercapnia (low O2, high CO2)

Question 2

What do you see on Type 1 RF ABG?

Answer 2

Low PaO2

Question 3

What do you see on Type 2 RF ABG?

Answer 3

Low PaO2
High PaCO2

Question 4

Discuss Type 1 Resp Failure

Answer 4

Hypoxemia with normocapnia
Usually occurs due to a V/Q mismatch
* Reduced ventilation and normal perfusion (e.g. pneumonia, pulmonary oedema, bronchoconstriction)
* Reduced perfusion with normal ventilation (e.g. pulmonary embolism)

As a result of the ventilation/perfusion mismatch, PaO2 falls, and PaCO2 rises. The rise in PaCO2 rapidly triggers an increase in a patient’s overall alveolar ventilation, which corrects the PaCO2 but not the PaO2 due to the different shapes of the CO2 and O2 dissociation curves.

Question 5

Discuss Type 2 Resp Failure

Answer 5

Hypoxemia with Hypercapnia
Occurs due to alveolar hypoventilation which prevents patients from adequately oxygenating and eliminating CO2 from their blood.
Hypoventilation can occur for several reasons, including:
* Increased resistance as a result of airway obstruction (e.g. COPD)
* Reduced compliance of the lung tissue/chest wall (e.g. pneumonia, rib fractures, obesity)
* Reduced strength of the respiratory muscles (e.g. Guillain-Barré, motor neurone disease)
* Reduced respiratory drive (e.g. opioids and other sedatives)

Question 6

Causes of respiratory acidosis

Answer 6

• Respiratory depression (e.g. opiates)
• Guillain-Barre: paralysis leads to an inability to adequately ventilate
• Asthma
• Chronic obstructive pulmonary disease (COPD)
• Iatrogenic (incorrect mechanical ventilation settings)

Question 7

Causes of respiratory alkalosis

Answer 7

• Anxiety (i.e. panic attack)
• Pain: causing an increased respiratory rate.
• Hypoxia: resulting in increased alveolar ventilation in an attempt to compensate.
• Pulmonary embolism
• Pneumothorax
• Iatrogenic (e.g. excessive mechanical ventilation)

Question 8

Discuss respiratory alkalosis

Answer 8

Respiratory alkalosis is caused by excessive alveolar ventilation (hyperventilation) resulting in more CO2 than normal being exhaled. As a result, PaCO2 is reduced and pH increases causing alkalosis.

A respiratory alkalosis would have the following characteristics on an ABG:

↑ pH
↓ CO2

Question 9

Discuss respiratory acidosis

Answer 9

Respiratory acidosis is caused by inadequate alveolar ventilation leading to CO2 retention.

A respiratory acidosis would have the following characteristics on an ABG:

↓ pH
↑ CO2

Question 10

What is the main IX for Resp failure

Answer 10

ABG