Respiratory Failure

Question 1

What is respiratory failure?

Answer 1

When the respiratory system fails to oxygenate arterial blood adequately and/or fails to prevent CO2 retention. Can be acute or chronic.

Question 2

What can cause respiratory failure?

Answer 2

• In an abnormality in any of the components of the respiratory system - airways, alveoli, capillaries
• Other causes: control of the resp system in the CNS/PNS, respiratory muscles, chest wall dynamics are abnormal

Question 3

Consequence of respiratory failure

Answer 3

Resp muscle fatigue, hypoventilation, sputum retention, hypoxaemia, resp acidosis, coma, cardiac arrest

Question 4

Type 1 Respiratory Failure

Answer 4

Oxygen (PaO2) of less than 8kPa (hypoxaemia) with a normal or low carbon dioxide (PaCO2).

DISORDER OF OXYGENATION/DIFFUSION
- Hypoxic hypoxaemia most common - can result in hypoxic tissues (time is different for each area)
(Fick’s Law - surface area x difference in concentration / diffusion distance)

Question 5

Type 2 Respiratory Failure

Answer 5

PaO2 of less than 8kPa (hypoxaemia) and an increase in PaCO2 levels greater than 7kPa (hypercapnia).

DISORDER OF VENTILATION (alteration to rate and depth of breathing). Balance between strength and load.

Question 6

What happens in normal respiration?

Answer 6

1. The transfer of oxygen across the alveoli
2. The transport of oxygen to the tissues
3. The removal of carbon dioxide from the blood into the alveoli and into the environment

In Type 1, 1 and 2 are compromised.
In Type 2, 1, 2 and 3 are compromised.

Question 7

How do we treat respiratory failure?

Answer 7

• Hypoxic hypoxaemia - remove secretions

- Type 2 - decrease load and increase strength

Question 8

Hypoxaemia - Give Oxygen?

Answer 8

Nasal Cannula - 2-4 litres
Mask (simple) - 4 litres
Mask (simple) - 4-15 litres
Hi Flow systems - 6-15 litres

Chronic patients can have HYPOXIC DRIVE so more O2 can be lethal.

Question 9

What is hypoxic drive?

Answer 9

Chronic patients (COPD, emphysema) may always be in type 2 respiratory failure as their bodies have learnt to adapt to the high amounts of CO2. It is normally high levels of CO2 which gets us to trigger a breath. In hypoxic drive, it is the low amount of O2 which triggers a breath. So if we give the chronic patient with HIGH CO2 and LOW O2 more oxygen, the body will think it has an adequate amount and stop that trigger to take a breath. Which can result in cardiac arrest.