Respiratory Failure

Question 1

What are the different types of respiratory failure?

Answer 1

Type 1 - Hypoxia with low PaCO2
Type 2 - Hypoxia with HIGH PaCO2

REMEMBER as 2 is the HIGHER number so has HIGHER PaC02.

Both type 1 and 2 have hypoxia. Respiratory failure occurs when gas exchange in inadequate resulting in hypoxia. Hypoxia is defined as a PaO2 < 8kPa

Question 2

What are the pathological consequences of hypoxia?

Answer 2

• Dyspnoea
• Restlessness
• Agitation
• Confusion
• Central cyanosis

LONG STANDING:

• Polycythemia (increased concentration of heamocrit, can be seen in long term COPD)
• Pulmonary hypertension
• Cor Pulmonale

Question 3

What are the pathological consequences of hypercapnia?

Answer 3

• Headache
• Peripheral vasodilatation
• Tachycardia
• CO2 retention flap
• Confusion
• Drowsiness
• Coma

Question 4

What do the ABG results of type and and type 2 respiratory failure show?

Answer 4

TYPE 1 RESPIRATORY FAILURE:
- Low PaCO2 levels so respiratory alkalosis

TYPE 2 RESPIRATORY FAILURE:
- High PaCO2 levels so respiratory acidosis

Question 5

What are the causes of type 1 respiratory failure?

Answer 5

• VQ mismatch
• Right to left cardiac shunts
• Abnormal diffusion
• Hypoventilation

Question 6

What are the conditions in which VQ mismatch occurs?

Answer 6

• Pneumonia
• Pulmonary oedema
• Pulmonary embolism
• Asthma
• Emphysema
• Pulmonary fibrosis
• ARDS

Question 7

What are the causes of type 2 respiratory failure?

Answer 7

Alveolar hypoventilation

=> Alveolar hypoventilation itself is caused by:

• Pulmonary disease
• Thoracic wall disease
• Neuromuscular disease
• Reduced respiratory drive

Question 8

What are the different ways of administrating oxygen?

Answer 8

NASAL CANNULAE - imprecise oxygen therapy

SIMPLE FACE MASKS - less precise than venturi and not used in type 2 respiratory failure, only type 1

VENTURI MASKS - provides exact % oxygen therapy

NON-REBREATHING MASKS - delivers high concentrations of oxygen used in emergencies

Question 9

What are the investigations in suspected respiratory failure?

Answer 9

=> Bloods
- FBC, U&E, CRP

=> ABG

=> CXR

=> Sputum and blood cultures

Question 10

Differential Diagnosis of Respiratory Failure?

Answer 10

• Hyperventilation secondary to metabolic acidosis
• Hyperventilation secondary to anxiety
• Obesity
• Sleep apnoea

Question 11

What is the management of type 1 respiratory failure?

Answer 11

• Treat underlying cause
• Give 28% oxygen by simple facemask
• Assisted ventilation if PaO2 < 8kPa despite 60% O2

Question 12

What is the management of type 2 respiratory failure?

Answer 12

• In type 2 respiratory failure, the respiratory centre may become insensitive to CO2 instead responding to oxygen levels
• controlled O2 therapy starting at 24%
• Recheck ABG after 20 mins, if PaCO2 has lowered, increase oxygen to 28%

IF PACO2 RISES ABOBE 1.5 kPa AND PATIENT STILL HYPOXIC, CONSIDER ASSISTED VENTILATION

Question 13

How does respiratory failure result in headaches?

Answer 13

• Build up of CO2 causes dilatation of blood vessels in the brain
• Increased pressure of fluid in the brain

Question 14

What is the clinical presentation of atelectasis?

Answer 14

Atelectasis is a common post op complication

• Normal vitals
• Lower zone fine crackles
• Lower zone lung collapse

Question 15

For those with COPD, what should be the target O2 levels

Answer 15

• Acutely ill patients, aim for 94-98%
• Patients at risk of hypercapnia, 88-92%
• For those patients where Co2 levels have resolved to normal, aim for 94-98%