Respiratory Failure

Question 1

What is the definition of respiratory failure?

Answer 1

A failure of the respiratory system to maintain adequate gas exchange

Question 2

What is the normal range for arterial oxygen partial pressures?

Answer 2

11.3-13.3 in young adults

But this falls with age

Question 3

What is the definition of type 1 respiratory failure?

Answer 3

Hypoxia PaO2 <8

Normal or raised carbon dioxide <6.0

Question 4

What is the definition of type II respiratory failure?

Answer 4

Hypoxia PaO2 less than 8

Hypercapnia PaCO2 greater than 6

Question 5

What causes type I respiratory failure?

Answer 5

V/Q mismatch- there is a compensatory increase in ventilation due to this which causes the carbon dioxide to fall.

Eg. PE, Pneumonia, Asthma, Pulmonary Oedema

Question 6

What causes type II respiratory failure?

Answer 6

Alveolar hypoventilation causes type II respiratory failure which leads to reduced exchange of carbon dioxide and so hypercapnia

E.g. COPD, Opioid toxicity, Pneumonia, Neurological disease (GBS, MND, Phrenic nerve injury)

Question 7

What are some signs and symptoms of hypoxia?

Answer 7

Cyanosis
Tachycardia
Confusion

Question 8

What investigations should be done to assess hypoxia?

Answer 8

Oxygen saturations

ABG

Question 9

How does hypoxia leads to metabolic acidosis?

Answer 9

Hypoxia causes a shift to anaerobic metabolism which causes production of lactate which forms lactic acid and this causes metabolic acidosis

Question 10

What are some symptoms of hypercapnia?

Answer 10

Hypercapnia causes vasodilation of the cerebral vessels. This causes headache.

Restlessness
CO2 retention tremor
Slurred speach
Reduced consciousness

Question 11

What type of acid base imbalance does hypercapnoea cause?

Answer 11

Respiratory acidosis

Question 12

What are the target oxygen saturations in a patient with known COPD?

Answer 12

88-92%

But high flow oxygen should be given in emergency situations.

Question 13

What might you see on examination of a patient with respiratory failure?

Answer 13

Increased respiratory rate
Use of accessory muscles
Cyanosis- Peripheral and central
Tachycardia
Evidence of Right Heart Strain- JVP, Hepatomegaly. Ascites, Pitting oedema

Question 14

When does the base excess go up?

Answer 14

When acid is added to the system e.g. DKA

Question 15

What is the management for respiratory failure?

Answer 15

Supportive and Definitive (Treat the cause)

Question 16

What is the supportive management for patients with respiratory failure?

Answer 16

Oxygen therapy

• Target 94-98% if healthy
• Target 88-92% if risk of carbon dioxide retention

Ventilation if unable to manage and carbon dioxide continues to rise

Question 17

What investigations are helpful in investigating the cause of respiratory failure?

Answer 17

Depends on the cause

Pneumonia or other infection- CXR, Sputum culture,

Malignancy- CXR, Bronchoscopy, CT

Heart Failure- CXR, BNP, ECHO, ECG,

PE- WELLS Score, CTPA, D-Dimer, V/Q scan

Asthma exacerbation- PEFR

Question 18

How should oxygen be given to COPD patients?- What should you start with

Answer 18

In a controlled manner using Venturi masks

Start with 28% Venturi mask at 4L/Min (White)

Recheck the ABG in 20 minutes and reassess. If the PaCO2 has gone up and patient still hypoxic consider assisted ventilation.

Question 19

When should ventilation be considered for patients with Type 1 respiratory failure?

Answer 19

Despite 60% oxygen PaO2 still less than 8

Question 20

What flow rate can be used for nasal cannula and what concentration does this deliver?

Answer 20

1-4 lites

24-40%

Question 21

When should non-rebreath masks be used?

Answer 21

For delivering high percentage oxygen in emergency situation. Inflate the bag and set to 15L.

Delivers 60-90% oxygen.